The absence of major proteomic alterations in the outer membrane between two cell types, together with the presented data on GFP activity in mutant strains, experimentally support the previously proposed continuum of the outer membrane and the periplasm in Anabaena sp. Also, somewhat different properties of the Anabaena sp. First, Alr protein, as shown here, is a TolC homologue present in both cell types. Second, phylogenetic analysis of the surprisingly abundant protein family of 24 TonB-dependent iron transporters in Anabaena sp.
Five members of this family are detected in the outer membrane of vegetative cells under iron-repletion and two of them, All and Alr, are explored closer. It is demonstrated that the function of these iron transporters is required for maintaining iron homeostasis of the filaments under iron-replete conditions. Consequently, their gene expression is constant and not enhanced by iron limitation. All and Alr have different specificity for siderophore substrates and in addition to iron transport, All protein is capable of copper uptake and influence on copper homeostasis in Anabaena sp.
Clean Aktueller Stand des Farbensehens der Pavianarten. Die vorliegende Arbeit vergleicht die detaillierten Strukturanalysen in der Retina von 4 Pavianarten mit den Untersuchungen in der Retina des Mantelpavians. Die daraus berechneten spektralen Empfindlichkeiten zeichnen sich durch gute Reproduzierbarkeit aus. Die Spektraldaten der Photopigmente der Mantelpaviane reihen sich in die Spektraldaten der Altweltaffen ein.
Bei den Mantelpavian Weibchen wird eine Variation von 2,0: Epstein-Barr Virus EBV is involved in several human malignancies via its latent gene products, which interact with cellular proteins and mimic discrete functions of cellular signalling pathways. Established in vivo model systems do not reflect the main aspects of EBV-associated diseases in humans. My PhD work aimed at engineering a transgenic mouse, which carries a conditionally inactivated EBV genome. This study took advantage of the well-established techniques of mouse genetics in order to stably integrate the entire EBV genome into the murine genome.
This approach would not only overcome the inability of EBV to infect animal cells but it would also permit to study the complete virus in an immunocompetent and easy-to-handle living organism. I undertook two routes to establish a transgenic mouse with the complete EBV genome inserted. One route was based on the site-specific integration into the hprt locus of murine embryonic stem cells. In addition, the EBV genome was genetically manipulated prior to its introduction into murine cells.
On the basis of the E. Two genetically modified and inversely oriented loxP sites were introduced in E. In transgenic animals this inversion can be reverted and the latent genes can be re-activated at will by cross-breeding with Cre-expressing mouse re-inversion. The ability of Cre to invert the big fragment was verified in infection experiments with human primary B cells. Despite sustained efforts, both gene delivery techniques did not lead to a transgenic mouse with the entire EBV genome inserted, but resulted in the integration of only subgenomic segments of the InvTarg recombinant EBV DNA.
A number of technical problems were identified during this work, indicating more specific direction for further research. On the basis of the experience gained here, the project of an EBV transgenic mouse can be carried on. In addition, the InvTarg maxi-EBV conditional vector might be employed in other experimental conditions, like different cell types or distinct stages of cell differentiation, for studies on latent EBV genes. Clean Proteomanalyse des bovinen Endometriums und zweier Oozytenstadien. Von den molekularen Signalen, die an dieser Interaktion beteiligt sind, sind bis heute nur wenige bekannt.
Diese so genannte Periimplantationsphase wurde anhand monozygoter Zwillinge analysiert. Auf Proteomebene wurden ungereifte mit in vitro gereiften bovinen Oozyten verglichen. Dihydrolipoamide S-Succinyltransferase und 6-Phosphogluconolactonase sind Enzyme des Energiemetabolismus. Die zugrunde liegenden onkogenen molekularen Mechanismen sind weitgehend unbekannt. B und p53 in der Arraytransfektion erfassen kann. Durch das Reportersystem konnte mit Hilfe der Arraytransfektion die HHVThymidinkinase als den Transkriptionsfaktor p53 induzierend ermittelt werden.
Dieser Prozess der Wachstumstransformation stellt ein Modellsystem dar, das die pathogenen Mechanismen in der Tumorentsteh-ung widerspiegelt. Many transcription factors integrate a variety of cellular stimuli to produce a transcriptional response. There is increasing evidence that the timing and kinetics of activation are crucial in determining specificity and strength of gene expression, however so far only few tools are available to address these questions in live cells and these have severe drawbacks, like very low signal strength, complicated handling, irreversibility and lack of good targeting properties.
Using fluorescence resonance energy transfer FRET we here develop genetically encoded indicators that enable imaging activation of CREB family transcription factors due to phosphorylation of the critical serine and subsequent recruitment of a coactivator in single live cells. After that, we analyzed the properties of ICAP in primary hippocampal neurons, where we characterize different signaling pathways with distinct kinetics that lead to CREB activation.
Furthermore, combining the imaging of CREB activation with calcium imaging we see a summation of CREB activation in neurons that can be achieved by appropriately timed depolarizing stimuli and occurs even when individual stimulations are separated by hours. On the whole, these array of biosensors complement the toolbox for the investigation of the activation of the CREB family of transcription factors in living cells and organisms.
JA und OPDA induzierten unterschiedliche Calciumsignaturen, die sich jeweils aus einer cytosolischen Calciumantwort gefolgt von einem Calciumsignal im Zellkern zusammensetzten. Clean Histone lysine methylation in the context of nuclear architecture. The impact of histone lysine methylation as an essential epigenetic mechanismn for gene regulation has been demonstrated by numerous studies where it was functionally and structurally linked to euchromatin and heterochromatin.
In this work the 3D architecture and spatial interrealtionships of different histone lysine methylation sites was investigated in various human cell types. Clean Cluster analysis and comparison of various chloroplast and nuclear transcriptomes in Arabidopsis thaliana. Clean Latent Epstein-Barr virus infection and the germinal center reaction. The development of the vascular network comprises tightly regulated processes, involving vasculogenesis and angiogenesis. The cells, which are mainly participating in these processes, are endothelial cells and vascular smooth muscle cells, the latter ones especially being important for the stability of blood vessels.
Uncontrolled proliferation of VSMCs contributes crucially to the development of vascular disease, e. Sox17, a member of subgroup F of the Sox family proteins, was for the first time detected in vascular smooth muscle cells in different mouse tissues, like liver, brain, heart, lung, spleen and kidney in vivo and in human coronary artery smooth muscle cells in vitro. Moreover, a new possible protein complex, consisting of SOX17, KLF4 and EGR-1, was found in human coronary artery smooth muscle cells, as well as in 4 day old embryoid bodies.
All members of this complex are induced by PDGF-BB, a growth factor which becomes activated in angiogenesis and pathological vascular conditions, stimulating the migration and proliferation of vascular SMCs. By this the complex might be involved in migration and proliferation of vascular SMCs, and moreover in pathological vascular conditions, like the progression of atherosclerosis.
Because of the fact, that a complex, consisting of Sox17, Klf4 and Egr-1, was also observed to be formed in differentiating ES-cells day 4 , supports a broader role of this protein complex in the differentiation of cell-specific lineages during development, in particular vascular smooth muscle cells and endoderm lineages. The complex might have an inhibitory, as well as an activating role, as Sox17, Klf4, and Egr-1 are known to behave bifunctional. At least this could be an indication for an involvement of the complex in modulating the wnt-signaling pathway during embryonic development.
Clean Study of protein-bacteriochlorophyll and protein-lipid interactions of natural and model light-harvesting complex 2 in purple bacterium Rhodobacter sphaeroides. The natural design of the photosystems of plants and photosynthetic bacteria using chlorophylls Chls or bacteriochlorophylls BChls as photoreceptors are robust. The basic principles of the biological system of light-harvesting complex 2 LH2 are studied with the use of natural and model sequences expressed in vivo in modified Rhodobacter Rb sphaeroides strains.
Three aspects have been explored in the thesis: Nevertheless, these residues are important for the structural thermal stability. Thus, the phytol chains were shown to be important for optimal pigment binding, especially for BChl-B; which appears to be highly sensitive to the proper packing of the phytols. Phospholipid determination of LH2 only expressing strains of Rb sphaeroides shows that the nonbilayer-forming phospholipid, phosphatidylethanolamine PE is present in elevated amounts in the intracytoplasmic membranes and in the immediate vicinity of the LH2 complex.
Specific local interactions between LH2 protein and lipids not only promote LH2 protein stability but appear to modulate the morphology of intracytoplasmic membranes. Based on these findings, the presence of LH2-lipid specificity is postulated. This gives rise to a better understanding of the interplay between BChl, apoproteins and membrane lipids in the assembly of a highly efficient light-harvesting complex in its native lipid-environment. Clean Population structure and speciation history of two closely related wild tomato species.
Die drei hierbei im Vordergrund stehenden Aspekte waren die pharmakologische Validierung der Lerntests, der regionenspezifische Nachweis neuronaler Aktivierung und Untersuchungen zur Expression lernspezifischer Gene. Quantitative Unterschiede wurden nicht gefunden. AMF-exploiting myco-heterotrophic plants don't perform photosynthesis, but receive all essential nutrients, including carbon from arbuscular-mycorrhizal fungi. In scope of this thesis five new species of AMF-exploiting myco-heterotrophic plants were described. In another species the anatomy of the subterranean structures and the fungal colonisation pattern were investigated.
The fungal hosts of eleven species from tropical Africa were identified by partial 18S rDNA sequence analysis. Das Indikatorgen selbst basiert auf der induzierbaren Transkriptionseinheit von HIV-1, die spezifisch durch das virale Protein Tat aktiviert werden kann und die Transkription eines Reportergens DsRed kontrolliert. Weder durch eine Colokalisations-Untersuchung noch eine Chromatin IP konnte jedoch eine spezifische Assoziation des episomalen Indikatorgens mit dem Histon H3 nachgewiesen werden. Clean Differentiation of dendrites and the analysis of spine- like structures on Lobula Plate Tangential Cells in Drosophila melanogaster.
The development of dendrites leads to the establishment of cell-type specific morphology of dendritic trees that eventually determines the way in which synaptic information is processed within the nervous system. The aim of this study was to investigate dendritogenesis of Drosophila motion-sensitive Lobula Plate Tangential Cells LPTCs and to understand the role of cytoskeletal molecules in these developmental processes. I employed genetic techniques to obtain fluorescent labeling exclusively in the neurons of interest. In order to visualize the LPTCs confocal imaging was applied.
Time point analysis allowed me to follow and describe the phases of LPTC differentiation in the intact Drosophila brain starting from the third instar larva throughout the pupal stages until adulthood. I determined the time when the initial growth of LPTC dendrites starts and showed it to be directional from the beginning. Additionally, I demonstrated that the phase of extensive dendritic growth and branching precedes reorganization processes that lead to establishment of the final architecture of LPTC dendritic trees.
In parallel, I attempted to analyze the contribution of actin and tubulin in the shaping of the neurons. In these experiments actin-GFP localized to dendritic termini whereas tubulin-GFP was mainly observed in the primary dendritic branches. These data showed clear similarities between the cytoskeletal organization of LPTCs dendrites and vertebrate neurons. The discovery of the actin enrichment in dendritic termini made me conduct a set of experiments to test if these protrusions are the counterparts of vertebrate spines. I performed a thorough quantitative analysis of spine- like protrusions present on LPTC dendrites.
Morphological features like the density and shape of the LPTC spine- like protrusions appeared to be comparable to hippocampal spines. Using immunohistochemical methods I demonstrated that LPTC spine-like protrusions are sites of synaptic contacts. The ultrastructural analysis supported the immunohistochemical data and showed that synaptic transmission takes place at the LPTC spine-like protrusions.
Next, I tried to genetically modify these structures by generating LPTC mutant for genes which have vertebrate homologues known to alter spine morphology. To conclude, I showed an initial description of LPTC dendritogenesis and the subcellular localization of actin and tubulin in these neurons. The actin enriched spine-like structures detected on the LPTC dendrites are sites of synaptic contacts, thus resemble vertebrate spines. Clean Identifizierung und Charakterisierung neuer Interaktionspartner des mitochondrialen Hsp Wie alle HspProteine arbeitet mtHsp70 dabei mit Cochaperonen zusammen.
In dieser Arbeit wurden neue Interaktionspartner von mtHsp70 identifiziert und funktionell charakterisiert. Ein bisher nicht bekanntes Protein wurde zusammen mit mtHsp70 aus S. Allerdings aggregieren in Abwesenheit von Hep1 mitochondriale HspProteine. Clean Mechanism of proteasome-mediated processing of proteins. Clean Histone H3 lysine 9 methylation: A signature for chromatin function. In most eukaryotes the histone methyltransferases SU VAR , G9a and their orthologues play major roles in transcriptional regulation.
Histone H3 lysine 9 methylation is associated to transcriptional silencing in vivo. A detailed analysis of the reaction products shows that recombinant SU VAR adds three methylgroups to full-length H3 and only two methylgroups to an H3-tail peptide. The transfer of two methylgroups to an unmethylated H3-tail peptide is achieved in a nonprocessive manner. The full-length enzyme elutes with an apparent molecular weight of kDa from a gel filtration column, which indicates the formation of a dimer. The N-terminus was shown to be required for this dimerisation and to retrieve full activity in vitro.
We show that the interaction occurs by domain swapping of two motifs within the N-terminus. The fact that the N-terminus is responsible for a concentration dependent dimerisation of SU VAR may indicate a role for this domain in the dosage-dependent effect on position effect variegation. Drosophila G9a adds three methyl groups to unmethylated H3 in vitro as has been described for mouse G9a. In vivo, dG9a is present in complexes with a molecular mass of kDa and we show that it specifically interacts with the histone deacetylase Rpd3.
HP1a is predominantly associated with centromeric heterochromatin in Drosophila. Supporting the histone code hypothesis, the chromo domain of HP1 recognises and binds H3K9 methylated peptides. The two HP1 paralogs HP1a and HP1c bind to distinct chromatin structures and we identify distinct interaction partners for these two proteins. Rac1 is a ubiquitously expressed member of the Rho family of small GTPases, which acts as a molecular switch by shuttling in a highly regulated manner between an active GTP-bound and an inactive GDP-bound state. Different signalling pathways, which involve integrins, growth factor receptors, cadherins as well as other Rho GTPases, can induce Rac1 activation.
Only in the GTP bound form, Rac1 can associate with different effector molecules to initiate cellular responses. Initially described as an important regulator of the actin cytoskeleton, Rac1 was later found to be also involved in the modulation of other processes such as cell adhesion, proliferation, survival, differentiation and migration. In epithelial cells, Rac1 was shown to regulate the formation and maintenance of cadherin dependent cell cell contacts, which are essential for the establishment of the polarized cell morphology. Before this project was initiated, almost all knowledge about the function of Rac1 was based on in vitro studies.
As constitutive deletion of the murine rac1 gene leads to early embryonic lethality, mice allowing for a conditional inactivation of the rac1 gene were generated in this study to enable the analysis of the function of Rac1 in selected tissues. To investigate the role of Rac1 in the epidermis and hair follicles and to determine its function in the establishment and maintenance of cell cell contacts between epithelial cells in vivo, mice with a keratinocyte-restricted ablation of the rac1 gene were generated and analyzed.
The results obtained in this study showed that the absence of Rac1 in the murine epidermis leads to a progressive hair loss but surprisingly has no effect on the maintenance of the epidermis. The hair loss is caused by the inability of hair follicle keratinocytes to maintain their differentiation state, which leads to the phagocytic removal of the non permanent parts of the hair follicles by infiltrating macrophages. In contrast, differentiation and proliferation of epidermal keratinocytes as well as the formation and maintenance of cell-cell and cell-matrix contacts, and the deposition of the basement membrane in the epidermis are not affected by the loss of Rac1.
Biochemical analysis of epidermal lysates demonstrated that the absence of epidermal defects in vivo is not a result of compensatory upregulation of closely related members of the Rho family of GTPases, further indicating that the function of Rac1 in epithelial cells in vivo is limited. Also, the analysis of the formation of the embryoid bodies from Rac1-deficient embryonic stem cells showed that the presence of Rac1 is not required for the establishment of cell cell contacts during differentiation of the polarized primitive ectoderm and for the formation of epithelial sheets, supporting the conclusion that the function of Rac1 in the regulation of cell cell adhesion between epithelial cells is dispensable.
However, the re epithelialization after wounding was impaired in the mutant epidermis, demonstrating that Rac1 plays an important role in pathological conditions. The delayed wound closure in the absence of Rac1 is caused by impaired cell migration and proliferation of neo epidermal keratinocytes. Another interesting finding of this study was the observation that, in contrast to the steady state in vivo situation, isolated Rac1 deficent primary keratinocytes display severe defects in cell culture, which lead to their detachment from the matrix. While the initial adhesion is only mildly affected by the lack of Rac1, mutant keratinocytes are unable to spread, show an impaired organization of the actin cytoskeleton and fail to form mature focal adhesions.
The differences between in vivo and in vitro effects resulting from the inactivation of the rac1 gene indicate that the function of Rac1 in epithelial cells depends on the complexity of the cellul. Clean Spatial echo suppression and echo-acoustic object normalization in echolocating bats. The processing of acoustic cues is critical for all animals in a wide range of behaviours including orientation, predator-prey interactions and social communication. The auditory system can process these sound information with amazing precision. Echolocating bats have developed an extraordinary ability to deal with acoustic cues.
Their echo-imaging system has enabled them to detect, pursue and capture tiny prey like insects, to avoid obstacles and to interact with their environment, often in total darkness. Bats heavily rely on the evaluation of echoes for orientation and hunting. The evaluation of external, echolocation- independent sounds also plays an important role for bats, e. The current thesis addresses two different aspects of the very complex echo-acoustic situation these extraordinary animals are confronted with in their daily life.
The first approach of this thesis is concerned with the question how bats deal with misleading spatial information of echoes. Acoustic orientation most often takes place in echoic environments. Accurate sound localization in natural, echoic environments is a vital task of the auditory system.
For a bat, this approach is also useful when localizing external, echolocation-independent sound sources, but it is in conflict with the processing of the echoes of self-generated sounds in an echolocation context. In a two-alternative, forced choice paradigm, it is investigated whether and to what extend the echolocating bats Megaderma lyra and Phyllostomus discolor spontaneously suppress the spatial information of either a second echo of their sonar emission or echoes of different external, echolocation-independent sounds. However, this suppression could not be confirmed in an exact repetition of the experiment.
Furthermore, it is shown that in the bat M. Abstract sounds like an acoustic impulse, a time-inverted contact call, or only the first syllable of the contact call do not induce spontaneous echo suppression. The current data indicate that while bats may be able to suppress the spatial information of echoes, this is not their default mode of auditory processing. The reason for this exceptional absence of spatial echo suppression may lie in the shorter time constants of cochlear processing in the ultrasonic frequency range and the strong influence of cognitive components associated with the precedence effect.
This study emphasises the contribution of high-level semantic auditory processing to echo suppression. The aim of the second approach was to characterize how echolocating Phyllostomus discolor deals with size-induced variations in echoes due to different-sized ensonified objects.
Echolocating bats can identify three-dimensional objects exclusively through the analysis of acoustic echoes of their ultrasonic emissions. However, objects of the same structure can differ in size and the auditory system must achieve a size-invariant, normalized object representation for reliable object recognition. This study describes the behavioral classification of echoes of complex virtual objects that vary in object size.
In a phantom-target playback experiment, it is shown that the bat P. To investigate the requirements of mitotic, kinetochore-associated proteins for human chromosome segregation we analyzed the human Ndc80 complex, a core structural component of the outer kinetochore. The Ndc80 complex contains Hec1 and Nuf2 that interact via their N-termini and a smaller subcomplex of Spc24 and Spc25 is linked to Hec1.
The complex is required for faithful chromosome congression and the recruitment of several proteins of the outer kinetochore, including the mitotic regulatory kinase Plk1. Moreover, PICH is a novel component of the spindle assembly checkpoint and PICH-dependent checkpoint signaling is likely to be mediated via kinetochore associated Mad2.
This study raises questions as to the fate of centromeric DNA in sister chromatid separation and its timing of decatenation. We speculate that this enzyme associates with catenated, centromeric DNA from prometaphase where it may be required to sense the tension between sister kinetochores. The presented thesis has focused on the interactions between protein and pigments in photosynthetic membrane proteins, and the significance of these interactions in membrane protein assembly.
The thesis has been divided into 3 Chapters, two are focused on the interactions between bacterio chlorophyll and proteins, and one is focused on the interactions, between carotenoid and proteins. In order to explore these interactions model proteins have been designed based on the peripheral antenna of Rhodobacter sphaeroides. In the model LH2 complexes, portions of the transmembrane helices, in particular, at the pigment binding sites, are replaced simplified alternating by alanine-leucine stretches.
In the model sequence context, the effects of particular amino acids are amplified, and thus allow for convenient identification of potentially critical interaction motifs. This approach is employed to study the factors that contribute to pigment binding and pigment-protein assembly. To confirm the significance of thus identified motifs, they are subsequently also examined in the WT sequence context. In Chapter 3, it is shown that the residue at position -4 of the beta-subunit has a critical structural role for the proper organisation of the excitonically coupled BChl dimer in the antenna complex.
In Chapter 4, the aspect of diastereotopic ligation to the central Mg of BChl is explored, in particular, the consequences of BChl-ligation for folding and assembly of BChl-proteins. The analysis of H-bonding patterns in Chl-binding photosystem I and II showed that H-bonding at the B Chl-protein interface is structurally distinct depending on the ligation type. Disruption of such H-bonding interactions by site directed mutagenesis significantly altered the structural stability and assembly of the LH2 complex in the membrane.
In Chapter 5, it is shown by mutational analysis of the carotenoid binding pocket of native and model LH2 complexes that the aromatic residues, in particular phenylalanine, are a key factor for carotenoid binding. The phenylalanine not only contributes to the stable Car binding but also lock the Car into a particular molecular configuration.
The importance of aromatic residues in Car binding is further supported by statistical analyses of the plant photosystems which show that phenylalanine residues are frequently in the close vicinity of Car moelcules. This study provides, to the best of our knowledge, the first experimental evidence for the central role of aromatic residues in carotenoid binding and functional specification. Clean Imaging brain-derived neurotrophic factor-mediated calcium signaling and plasticity in developing neurons. Weiterhin wurde eine kleine Stichprobe von zehn modernen kremierten Knochen analysiert.
Clean Variations of the ectomycorrhizal community in high mountain Norway spruce stands and correlations with the main pedoclimatic factors. The species composition of ectomycorrhizal ECM fungal communities can be strongly influenced by abiotic and biotic factors, which determine interactions among the species such as resource partitioning, disturbance, competition, or relationships with other organisms. In order to determine the influence of environmental features on ECM community, soil bedrock pH, exposure, humus features and sampling points locations were taken into account as the most representative and influencing factors in these soil ecological dynamics.
The investigation of the ECM community composition species richness and abundance in relation to the main pedoclimatic factors revealed the importance of bedrock pH and site exposure as variables at a macro-scale level. A spatial niche differentiation of ECM species and ecological ECM groups, based on similar organization and extent of the extramatrical mycelium, were mostly associated to organic layers OF , pH and N tot variables at a vertical micro-scale level of study.
The results suggest that bedrock pH, exposure and humus dynamics play a primary role in the adaptive selection of ECM species constituting the consortium. Regulation, Funktion und neue Substrate. Da Zellen ohne Securin ihre Chromosomen jedoch akkurat und zum richtigen Zeitpunkt trennen, muss es alternative Separase-Inhibitionsmechanismen geben. Die beiden Inhibitoren sind also Komponenten parallel und nicht konvergent wirkender Regulationsmechanismen.
Cdc6 ist ein konserviertes Protein, das in S. Serin Phosphorylierung ist dagegen indirekt an der Kinase-Bindung beteiligt. Denn erstens wird sie nach. Clean Protein fragment complementation assay for studying viral protein-protein interactions. Herpesviruses cause highly prevalent infections associated with usually mild symptoms resulting in life long latency. However, they can provoke fatal disease in susceptible individuals such as immunocompromised patients either in the context of primary infection or after reactivation from latency.
Despite of their emerging medical importance, herpesvirus infections can so far only be controlled by antiviral therapy targeting viral DNA replication, accompanied with side effects and occurrence of resistant strains. In this work, a novel platform for drug discovery was established that is based on a protein complementation assay PCA , which can be used to study viral protein-protein interactions in a simple cell based assay.
In a PCA two inactive fragments of a reporter enzyme are fused to two interacting proteins. Interaction of the proteins leads to proximity of the enzyme fragments, followed by reconstitution of the reporter enzyme activity. Members of the UL34 and UL31 families are conserved herpesvirus proteins. They interact with one another forming the nuclear egress complex NEC , which is essential for the export of viral capsids from the cell nucleus. This crucial protein-protein interaction might serve as a potential drug target for anti-herpesvirus chemotherapy.
In this work the mutual binding sites of the two proteins were localized and studied for their conservation. The assay was validated and applied to representative members of the three herpesvirus subfamilies. Cross-complementation assays showed that partners derived from the same subfamily can replace each other in the PCA, however, homologues from different subfamilies can not. This cross-complementation reflects the in vivo situation: The lack of complementation between the subfamilies is due to their diverged binding sites, which are located in all cases within the first conserved region of the UL31 family proteins.
The study of the binding site in UL34 family members revealed a bipartite binding motif. The increased incidence of psychiatric disorders, such as anxiety disorders and depression, makes a strengthened search of genetic and environmental causal factors essential. Besides clinical studies, the broad preclinical research identifies continuously involved neuronal circuits, proteins, and genes representing new candidates in the progress of pharmacological research and the development of new therapies.
In this context, an animal model of extremes in trait anxiety, simulating pathologic anxiety, was generated to investigate the neuronal and genetic basis. Thus, CD1 mice selectively and bi-directionally inbred concerning their anxiety-related behavior form two lines, the high HAB and the low LAB anxiety-related behavior mice. The two lines display, after 24 generations, robust differences in trait anxiety and, additionally, in depression-like behavior, reflecting the clinical comorbidity of anxiety and depression, both of which are potentially based on a few selected genes in the two lines.
The peptide arginine-vasopressin AVP is one factor found to be differentially expressed between the two mouse lines. In the present manuscript its involvement in the behavioral phenotype is scrutinized. As the antidiuretic hormone, AVP expressed in the hypothalamic paraventricular nucleus PVN and the supraoptic nucleus is well known to regulate peripherally the body water balance. Therefore, the physiological consequence of the differences in Avp expression was analyzed, uncovering signs of central diabetes insipidus in LAB mice, an AVP deficit-related disease in humans.
Symptoms also seen in LAB mice are increased daily fluid intake and high amounts of highly diluted urine as a result of the inability to secrete enough AVP in the blood circulation. Besides the antidiuretic function, AVP of the PVN is potentially involved in emotionality-related behaviors and further in the regulation of the hypothalamo-pituitary-adrenocortical axis, the neuroendocrine stress response.
Thus, the peripherally observable strong deficit in AVP might also be present in the brain of LAB mice, causing a dysregulation of anxiety-related behavior in these animals. Therefore, we tested the maternal rearing behavior of HAB and LAB dams for differences possibly involved in the development of the two phenotypes.
As dams of the two lines differ in their nursing style with LAB mothers showing less arched back nursing, a posture associated with the quality of maternal investment, we cross-fostered pups of the two lines to quantify the maternal influence on the anxiety- and stress-related phenotype of HAB and LAB mice. As we found just slight shifts in some parameters still within the range of the HAB and LAB phenotype, the two breeding lines can be defined as mainly genetically distinct, providing a beneficial tool to identify genes responsible for pathologic alterations in human diseases.
The major goal of the project was the investigation of proteins that regulate dynamic rearrangements of the actin cytoskeleton in Dictyostelium discoideum amoebae. Among the proteins studied in detail were i D. Filopodia are bundles of actin filaments projecting from the cell surface. They are found on a variety of cell types and are needed among others, for cell adhesion, sensory and exploratory functions. Filopodia are frequently found associated with sheet-like arrays of actin filaments called lamellipodia and membrane ruffles.
The in vitro nucleating activity of DdVASP is salt dependent and its nucleating activity is completely abolished at mM salt. However, the F-actin bundling activity as determined by the low speed sedimentation assay was not disturbed. The ability of DdVASP to influence the binding of capping protein to the growing ends of the actin filaments was tested through elongation of capped F-actin seeds and by depolymerization of capped filaments upon dilution below the critical concentration of the barbed ends.
Results from both sets of experiments showed that DdVASP cannot remove capping protein from the barbed ends. In vitro biochemical data led to the conclusion that the bundling activity of DdVASP is the essential in vivo function to stabilise actin filaments in emerging filopodia. As expected the mutant failed to produce any filopodia. The results indicated that VASPs are functionally well conserved throughout evolution. During this study, a third profilin isoform, profilin III, was further characterised.
Profilin III shares a limited homology at the amino acid level with the other two and well studied profilins. This suggests a distinct role for profilin III, because a low protein concentration argues against an actin sequestering function. Immunolocalisation studies showed profilin III in filopodia and enriched at their tips. Cells lacking the profilin III protein show defects in cell motility during chemotaxis. The second part of the project dealt with the characterisation of two D.
The regulatory region harbours the putative inhibitory domain aa and a possible multimerization SARAH domain aa de. Notch-Signale spielen bei der Entwicklung von Lymphozyten eine wichtige Rolle. Die Expression von Zielgenen wurde anhand einer Microarray- Analyse untersucht. Notch2IC konnte Gene induzieren und Gene reprimieren. Genes are of two kinds: All organisms use the same genetic language for their instructions The genetic code is translated into a sequence of amino acids that makes up the protein.
Almost all organisms use the same genetic code 6. Why do we, and other organisms, vary in how we look and function? There are patterns of gene transfer across generations. Cellular and molecular mechanisms drive these patterns and results in genetic variation. The environment interacts with our genetic make-up leading to genetic variation. Man can alter and manipulate the genetic make-up of organisms for the benefit of human life.
H Environmental factors can interact with our genetic information The environment can affect our traits. Even organisms that are related may end up looking or behaving differently The environment can influence cell function throughout changes at the protein level type and amount Environmental factors can cause mutations in genes, or alter gene expression I Man can alter and modify the genetic information.
Advanced technology has enhanced this action. Man uses several techniques to improve the quality of animals and plants Man can manipulate the genetic information and cause change in traits New varieties of farm animals and plants arise by transgenesis and other gene transfer techniques used by man. Genetic engineering is used to provide therapy for certain genetic diseases Bizarre and new creatures occur as a result of gene manipulation by man.
Advanced DNA technology helps improve the health quality of humans 7. Students across all grade levels had a low level of genetic literacy as they failed to answer questions on how genetics related to society, technology, and the environment. Students and teachers attributed difficulty in understanding genetics concepts to the poor quality of the national biology textbook which lacks coherence and logical sequencing of concepts, is overloaded with material, does not encourage critical thinking, does not match students cognitive level, and does not link genetics to everyday life.
Students also underlined the use of traditional teaching methods as another major reason for the difficulty they face in understanding core ideas in genetics. Content analysis of the genetics curriculum showed lack of developmental progression across the grade levels, misalignment between content and objectives, absence of ethical and moral life-related issues, and shallow coverage of STS genetics issues.
Teachers and students evaluation of the LP-driven genetics unit revealed that the objectives and content were aligned, the concepts were coherent and logically sequenced, the content promoted genetic literacy, and the activities and assessment items encouraged critical thinking. This was consistent with the students opinions in the focus groups in which they indicated that the newly designed genetics unit had a clear and logically organized content which is enriched with quality illustrations, figures, questions and real-life examples that enhanced their understanding of genetics. Also, students still found the concepts of mitosis and meiosis very difficult and confusing.
Results suggest two possible sources of these misconceptions and difficulties: Moreover, although the LP-driven genetics unit favors group-discussion, use of inquiry, lab activities, and technology in instruction, classroom observations showed that teacher-centered methods dominate genetics instruction. On the contrary, the student-centered approach illustrated in the designed unit is imperative, especially for deep understanding of the abstract concepts of genetics. When asked to explain her approach, the biology teacher argued that time constraints, the overloaded curriculum, and student preparation for official exams resulted her traditional teaching methods.
Such impediments may lower students motivation to learn genetics. Moreover, classroom observations provided evidence that the language of instruction English is another major factor which might hinder students learning, since it is different from their native tongue Arabic. Jointly, all the factors mentioned above are possible explanations for Lebanese students persistent difficulties in understanding genetics concepts. When students do not have a firm grasp of basic genetics concepts in earlier grade levels, they carry their misunderstandings and misconceptions with them as they progress to higher grade levels.
As a result, students are reaching higher grade levels without an adequate knowledge base that is necessary for understanding more complex genetics concepts. In terms of validating the effectiveness of the genetics unit that was based on the LP, teachers and students feedback provided evidence that the new unit addressed the major problems of the existing curriculum. Surprisingly, however, findings of this study showed that students from both experimental and control groups performed equally well on most of the post-test items.
One possible reason may be the fact that the teacher used some activities included in the new genetics unit for both classes because of her perception that the unit was better adapted to students needs. This could have happened when the researcher was not conducting classroom observations. Other reasons include the lack of proper implementation of the unit, the teacher s weak content knowledge, among other possible reason.
This study presents several implications for practice. First, there is a need for an extensive revision of the Lebanese genetics curriculum. Second, proper sequencing of core concepts and sub-concepts is necessary, using LP as a framework, to enhance students understanding of 9. The best curriculum would fail if teachers are not offered the opportunity to be trained in strategies for the proper implementation of the designed curriculum. In addition, student-related factors e. As a result, it is highly recommended that schools, curriculum designers, and universities establish partnerships with the government to refine scholastic programs based on research in an attempt to nurture students, the knowledgeable citizens.
A learning progression for deepening students understandings of modern genetics across the 5thth grades. Reasoning across ontologically distinct levels: Students understandings of molecular genetics. Aligning curriculum, instruction and assessment. The emergence of a learning progression in middle school chemistry. Findings from the high school biology curriculum study: Molecular basis of heredity. Traits, genes, particles and information: Re-visiting students understandings of genetics. Linking an educative learning progression to teacher practice: Results of an explanatory study.
National Research Council Taking science to school: Learning and teaching science in grades K The national Academic Press. Mapping a coherent learning progression for the molecular basis of heredity. Genetic reasoning with multiple representations. Journal of Research in Science Education, 33,. Tellefsen 2 and Ellen K. Quantum physics is a fascinating but also challenging topic in physics at preuniversity level. This study has investigated how students in upper secondary schools in Norway understand the concept of quantization and the wave-particle duality for light while working with digital resources developed in the project ReleQuant, where qualitative understanding and use of language is emphasized.
Data were collected by means of students written responses to tasks on the digital platform, and by discussions between peers recorded on students own cell phones. It was found that the concept of quantization was poorly understood and often mistaken as quantification. For the wave-particle duality it was found that many students refer to the dual nature of light without paying attention to the contradiction between the models.
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However, some good student responses also indicate that qualitative understanding of quantum physics is possible even on pre-university level. The results contribute to the relatively scarce research literature on student understanding of modern physics on pre-university level. In ReleQuant, results are also used for further development of teaching resources, in line with the Educational Design Research methodology. New versions of the resources pay attention to students problems in understanding of the concept of quantization and emphasize the contradiction between a wave model and a particle model for light in a classical sense.
Implications are discussed for design of teaching resources that support students in reflecting on how quantum physics breaks with classical physics and on its epistemological implications. Quantum physics, student conceptions, Educational Design Research. Theories in quantum physics break with our everyday experience of natural phenomena and with classical physics in fundamental ways that often fascinate young people. However, relatively little research has been undertaken to investigate students conceptions and learning processes in quantum physics on pre-university level.
In contrast to the situation in most other countries, the Norwegian curriculum for physics in upper secondary school gives opportunities to explore interpretations of quantum physics and relativity and discuss the philosophical and epistemological consequences of theories in modern physics Henriksen et al. The curriculum provides opportunities for students to explore the philosophical foundation for quantum physics, how it breaks with classical physics and its epistemological consequences.
This paper reports results from the project ReleQuant, which combines research and development in developing digital teaching resources in quantum physics and theory of relativity by means of methodology from Educational Design Research see Bungum et al. In the development of resources we emphasise qualitative understanding in line with the curriculum requirement, students reflection and their use of written and oral language in the learning process.
The teaching material also exposes students to the nature of science in terms of how quantum physics developed historically, that physicists still disagree on interpretations, the implications of modern physics for our view of the world, and the use of quantum physics in modern technology. The specific study presented here investigates how Norwegian upper secondary physics students interpret fundamental principles in quantum physics before and during work with the digital teaching resources developed in the project ReleQuant.
We focus on two fundamental principles in quantum physics; the wave-particle duality for light and the concept of quantization. Research questions for the study are: How do upper secondary physics students interpret the wave-particle duality for light? How do upper secondary physics students interpret the concept of quantization?
The results contribute to the further development of ReleQuant resources, and in the discussion in this paper we will point to specific changes made in the resources based on the results. The study also has a more general value by throwing light on how upper secondary school students may perceive fundamental principles in quantum physics, and the opportunities and challenges in teaching quantum physics in qualitative ways on preuniversity level.
In mechanics, for instance, research has focused on how the physical description of e. In quantum physics and relativity, challenges are of a different nature, since these topics concern phenomena that cannot be visualized or experienced directly and where classroom experiments may be difficult or impossible to undertake.
Research on university students conceptions of quantum physics indicates that their understanding is often fragmented and dominated by isolated facts not fitted into an internally consistent conceptual framework Hadzidaki, This may be due to how quantum physics on university level is dominated by mathematics and abstract formalism.
Pospiech pointed out that even if quantum physics cannot be fully understood without mathematics, the mathematical formalism often hides the philosophical issues important for understanding the full depth of modern physics. Based on a study of pre-university students understanding of quantum physics, Ireson gave five recommendations for teaching the topic: Avoiding reference to classical physics; 2. Teaching the photoelectric effect by beginning with electrons rather than photons; 3. Using statistical interpretations of observed phenomena and avoiding dualistic descriptions; 4.
Introducing the Heisenberg uncertainty principle for ensembles of quantum objects at an early stage; and 5. Avoiding the Bohr model in the treatment of the hydrogen atom. Ayene, Kriek and Damtie investigated university students conceptions of the waveparticle duality, and found that most students described light in terms of classical models of waves and particles, or as mixed models with aspects of quantum physics combined with Olsen found that the wave-particle duality was poorly understood by senior high school students in Norway, and some students clearly demonstrated misconceptions rooted in a classical physics worldview.
One misconception identified was the view of light as particles moving in a wave-shaped trajectory. Cheong and Song , in their study of university student conceptions, identified three levels of meaning of duality. The first level entails that light has both particle and wave properties, without any reference to a wave function.
The third level includes an understanding of different interpretations of quantum theory, linking the theory to experimental observations. The first level of meaning of duality is most relevant to the Norwegian senior high school physics curriculum, since it describes a qualitative approach to quantum physics. However, the curriculum states explicitly that students should reflect on philosophical aspects of quantum physics and how it breaks with classical physics.
This requires that students understanding of wave-particle duality moves beyond a statement that it is both waves and particles. Singh pointed to the importance of visualizations for students in order to build links between formal and conceptual aspects of quantum physics.
Hadzidaki , discussing teaching and learning in quantum physics, argued that students need to be made aware of the ways in which quantum physics represents a break with the principles of classical physics. This break and its epistemological consequences is an important objective in the Norwegian physics curriculum. METHOD Data for the study presented in this paper were gathered from students work with the digital ReleQuant material in physics classes during three subsequent cycles of development over the period March March Eight classes at five different upper secondary schools participated, involving around students taught by their regular teacher.
Two kinds of data were collected for this study. Firstly, written student responses to questions in the ReleQuant teaching module were collected through the digital platform. For light, this firstly involved a question at the beginning of the teaching where students are invited to describe in writing what they think light is, based on their prior knowledge. Secondly, student discussions were recorded when students were asked to compare their written responses in pairs. For quantization, students were first challenged to suggest everyday entities that are quantized and respond in writing.
Then they did audio recordings of peer discussions on these suggestions. Student discussions in pairs were recorded on the students own cell phones and ed by students to their teacher after the session. To some extent we have counted responses and reported as percentages of responses within categories of responses. However, since students partly worked in pairs and student numbers were varying during the sessions, we present the results mainly qualitatively with semi-quantitative measures in order to indicate how prevalent various student conceptions appear to be.
Some of these students described the experimental evidence supporting each view, in particular interference patterns as a sign of wave properties. However, many students dealt with the two models in combination without further elaboration. For example, one student wrote: Light is energy in the form of small particles, photons. Light gets different colors depending on which wavelength it has. These responses indicate that students hold parallel conceptions of light as waves and particles, without considering the contradiction between these two models.
It is hard to determine what a photon is. Even researchers disagree, there are many explanations and definitions. They behave differently depending on the perspective you take Recorded oral discussions among students confirm the impression that students may think of light in different ways without recognizing any contradiction. For example, in the following dialogue student A speaks of light as electromagnetic waves, while student B explains it as a stream of photons and small particles: What are photons and light, really? It s an electromagnetic wave, isn t it?
Light is simply a stream of photons, then. Yes, you could say that. Photons, then, are A: And then we have - B: Photons are very small, indivisible particles. The students here seem to think they agree on a common understanding, yet they refer to very different models for light. Students conceptions of quantization Concerning quantization, respondents were asked to think of everyday examples of quantized entities.
Many came up with adequate examples such as the number of book pages in a library and the number of persons in a room. However, the students audio-recorded discussions reveal that the ideas underpinning their examples often entail a weak understanding of what quantization means. Their ideas range from quantization as any entity that is countable as integer numbers in principle or in practice, e.
Many also mixed up the phrases and in many cases the concepts quantization and quantification, as in this statement where the student perceives quantization as entities that can be counted as integer numbers: Quantification is, well it is to divide into certain levels, like in everyday life you can say that you have a certain number of friends. You cannot have half a friend. You can have 1,2,3 You can have an integer number. The following response, where the student uses a chain as an analogy, is a very good, but rare, example of how some students expose a good understanding of what quantization means: Like a chain has a smallest value of length.
Because the length must be divisible with the length of one chain ring, in contrast to a thread that you can cut in any length you want. So the thread will be an example of something continuous when you cut the length, while a chain sort of has to make steps in lengths, and is not continuous, because you must consider the chain rings. So the chain is quantized. For most students, however, it was challenging to find good everyday examples of quantized entities in the sense the concept is used in physics.
The problem is reasonable, since quantization beyond the trivial integer number examples is not easy to find in everyday life. Although our sample is not adequate for a statistical generalization, we anticipate that similar student conceptions also will be present in other classrooms. The results indicate that most students are well aware that light can be described as both waves and particles.
Some refer to the experimental basis for the two descriptions, but only few respondents discuss the two models as complementary or seemingly contradictory. It seems that students try to combine the wave and particle view of light in ways that avoid the contradiction between the two models. For some, this leads to the misconception described by Olsen , that the wave-particle duality means that particles are moving in a wave-shaped trajectory. Others speak of energy packages in ways that fit how photons often are drawn in textbooks as short pieces of a wave.
This visualization of a photon helps students combine a wave and a particle in one single conception, but may mask the break between classical physics and quantum physics, and may not be constructive in developing a deeper understanding of quantum physics. The results as a whole confirm the results reported by Ayene, Kriek and Damtie , where students stick to classical conceptions and images in interpreting quantum physics.
These results indicate that teaching of quantum physics should emphasize how quantum physics break with classical physics in fundamental ways. For the Wave-particle duality, this means that students should be made aware of the contradiction between a wave model and a particle model for light interpreted in a classical sense. This might help students avoid the typical misconceptions that are rooted in classical models. Exposing to students how different and conflicting interpretations exist among contemporary physicists may also stimulate their own epistemological reflections and illustrate how science is in continuous development, thus supporting a more nuanced view of the nature of science.
Figure 1 shows a screenshot from the next version of teaching resources, designed to make students more aware of how classical conceptions of a wave and a particle can not be combined in meaningful ways, since a wave is extended in space while a particle is a point or a very small object. Students are here encouraged to discuss whether it is possible that light can be simultaneously a wave and particles, in order to make them aware of the shortcomings of classical models in quantum physics.
Screenshot of ReleQuant page emphasizing how a wave model and a particle model for light contradict each other in a classical sense. For quantization, recorded student discussions indicate that a surprisingly large number of students hold insufficient understanding or mistaken ideas on what the concept quantized means.
Many respondents focused on how quantization concerns countable entities, whereas very few responses involved the idea of discrete levels or values. Some responses seem to be influenced by a confusion of the concept quantized with quantified. The first prototype of the ReleQuant resources encouraged students to use everyday examples in order to elaborate on the concept of quantization.
However, as results from the trials in classrooms exposed that many students had weak conceptions of quantization and that some students acquired limited or mistaken understanding by means of everyday examples, the resources were changed in this regard. Rather than focusing on everyday examples, the next version of the resources invite students to go deeper into the physics and how the issue of quantization can be traced back to ancient philosophy of nature. Even if research in physics education has warned against the use of the Bohr model for the atom e.
Ireson, in teaching modern physics, we find it useful to build on students familiarity with this for illustrating quantization of energy. Figure 2 shows a screenshot of the resources where energy levels in the hydrogen atom are contrasted to the continuously changing kinetic energy of an oscillating spring in order to illustrate the difference between quantization and continuity in the case of energy. The presentation of quantization from a historical perspective is shown in Figure 3.
This includes links to Einstein presentation of the photon in original and translated version. Screenshot from ReleQuant page comparing continuous energy in a spring and quantized energy in the Hydrogen atom. Screenshot from ReleQuant page presenting the concept of quantization from a historical perspective. The use of language and student discussions in ReleQuant has contributed to exposing student conceptions in quantum physics as multifaceted. Even if students are often able to give adequate examples and definitions such as those found in textbooks, their discussions reveal that fundamental concepts in quantum physics are poorly understood.
However, some good responses from students indicate that a deeper qualitative understanding of quantum physics is possible even on pre-university level, in the case of wave-particle duality this means progressing through the second and third level of meaning of duality as described by Cheong and Song As Pospiech has suggested, there is a clear need in teaching to go deeper into what fundamental concepts mean when teaching about quantum physics, and to express their significance for our understanding of the physical world.
Moreover, more research is needed and will be continued in repeated cycles of design and classroom trials in ReleQuant to establish evidence-based knowledge on how teaching material can be designed to support students qualitative understanding and epistemological reflections in physics. Acknowledgement The research is supported by the Research Council of Norway. Wave-particle duality and uncertainty principle: Phenomenographic categories of description of tertiary physics students depictions.
Using thematic analysis in psychology. Qualitative Research in Psychology, 3 2 , Bungum, B. ReleQuant - Improving teaching and learning in quantum physics through educational design research.
Fakultät für Biologie - Digitale Hochschulschriften der LMU - Teil 02/06
NorDiNa, 11 2 ,. Constructing Scientific Knowledge in the Classroom. Educational Researcher, 23 7 , doi: Relativity, quantum physics and philosophy in the upper secondary curriculum: Physics Education, 49 6 , The quantum understanding of pre-university physics students. Physics Education, 35 1 , Myhrehagen, H. Introducing quantum mechanics in the upper secondary school: Physics Education, 35 6 , University of Oslo, Oslo.
Interactive learning tutorials on quantum mechanics. American Journal of Physics, 76 4 ,. Learning is a life-long process and constructing a good learning framework for students is essential in order for them to be productive students throughout their lives. To construct and connect concepts to develop a framework which links content in a concept building process seems to be a better option than to merely flooding students with overwhelming terms and knowledge without making logical connections.
According to Cheema and Mirza , Buldu and Buldu , Horton, McConney, Gall, Woods, Senn and Hamelin concept mapping is one strategy, which has shown promise in being a significant teaching-learning strategy. After various informal discussions with Natural Sciences teachers it became clear that only a few of them utilise concept maps as a teachinglearning strategy.
This study investigated the role of concept mapping as a teaching-learning strategy in South African Natural Sciences classrooms. A quasi-experimental design was utilised for this study. Two Grade 8 Natural Sciences classes took part in this investigation, 48 students participated in the study, 24 within the control group and 24 within the experimental group.
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Both groups completed the pre-test questionnaire, both groups wrote the pre-test assessment on the topic scientific investigation, both groups wrote the post-test assessment on the learnt topic, and only the experimental group completed the post-test questionnaire. The results revealed that concept maps play an important role in Grade 8 Natural Sciences classrooms and although students prefer constructing maps in class, to constructing it on their own, they do use concept maps as a study strategy in preparing for the exams.
According to Nesbit and Adesope and Willis and Miertschin pictures and visual learning may help students to retrieve prior knowledge about the concept and therefore can be used to imbed the knowledge and enhance retrieval. Concept maps take ideas and pictures, which radiate out from a central concept, capturing a specific topic in a non-linear fashion through incorporating graphics and colours Budd, Thus tapping into visual learning and connecting with students whose learning style is not as well served by linear, text-based materials.
To adapt practices that encourage meaningful learning, it seems evident that teachers must also seek to learn ways in which subject matter can be taught meaningfully, by using knowledge representative systems that are useful in classroom settings. Students registered for the Post Graduate Certificate in Education PGCE at our institution need to do action research during their seven weeks of Work Integrated Learning WIL and submit their research report as an exam equivalent at the end of the year.
After various informal discussions with practicing Natural Sciences teachers it became clear that secondary school students are flooded with overwhelming terms and knowledge without constructing and connecting concepts to develop a framework which links content together in a concept building process. Only a few of these practicing teachers indicated that they utilise concept maps as a teaching-learning strategy.
One of the PGCE students thought it worthwhile to investigate the role of concept mapping as a teaching learning strategy in Natural Sciences classrooms in order to view what implications the utilization of concept maps may have on the academic achievement of these students.
Research questions The study addressed the following questions: Do Grade 8 students use concept mapping as a learning-strategy in Natural Sciences? Does the academic achievement differ between a Grade 8 control group not taught with concept maps and a Grade 8 experimental group taught with concept maps? What are the students opinions on the role of concept mapping on their academic achievement when utilized in the classroom by their Natural Sciences teacher during the teaching-learning process?
What are the students opinion on the role of concept mapping on their academic achievement when they utilize concept maps while preparing for a class test? Permission to carry out the research was given by the school principal. Students and their parents were informed about the study and their permission to allow their It was emphasised to all the parties involved that participation would be voluntary and that complete confidentiality would be maintained.
Two Grade 8 Natural Sciences classes were assigned to the study by a school in Gauteng. The study was conducted over a seven week period where two Grade 8 classes class 8. There were 24 students in each of these two groups. On day one both groups were given a questionnaire based on concept mapping to establish whether the students utilize concept mapping as a learning strategy. An assessment task as a pre-test on the topic scientific investigation was then given to both groups. On day two the students from the experimental group were taught how to construct a concept map.
The next three days both groups were taught on the current topic which correlated with the prescribed curriculum.
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The experimental group was taught through the construction of a concept map and were asked to learn and study with the aid of the concept map. The control group was taught using the traditional teaching strategy and were asked to learn and study the topic without the use of concept maps.
During the next class both groups did an assessment task as a post-test based on the topic scientific investigations. The control group was then given a presentation on concept mapping and the construction thereof to avoid any bias that might have arisen. During the next few weeks both groups were taught with the aid of concept mapping as a teachinglearning strategy.
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Quantitative replacement of citrate by phosphane on silver nanoparticle surfaces monitored by surface-enhanced Raman spectroscopy SERS ,. Journal of nanoscience and nanotechnology, Vol. Quaternized polysulfone and graphene oxide nanosheet derived low fouling novel positively charged hybrid ultrafiltration membranes for protein separation,.
Rapid doping of conventional polymers with laser-generated nanoparticles for optics, magnetics, energy and biomedical application,. Rational design of nanoparticle toxicology assays: Record figure of merit values of highly stoichiometric Sb2Te3 porous bulk synthesized from tailor-made molecular precursors in ionic liquids,.
Journal of materials chemistry C: Reproducibility of retention time and peak area in comprehensive two-dimensional liquid chromatography,. Ripening kinetics of laser-generated plasmonic nanoparticles in different solvents,. Selective elimination of bacterial faecal indicators in the Schmutzdecke of slow sand filtration columns,. Applied microbiology and biotechnology, Vol. American Institute of Physics Inc. Selective transport of Fe III using polyeugenol as functional polymer with ionic imprinted polymer membrane method,. Selectivity screening and subsequent data evaluation strategies in liquid chromatography: Sex selection of sperm in farm animals: Size control and supporting of palladium nanoparticles made by laser ablation in saline solution as a facile route to heterogeneous catalysts,.
Size controlled and stable ligand-free palladium nanoparticles for heterogeneous catalysis,. Range, Sven; Bernardes, Carlos E. An experimental and computational study of the influence of particle size on the lattice energy of NaCl,. The journal of physical chemistry C: Solid solution magnetic FeNi nanostrand—polymer composites by connecting-coarsening assembly,. Specific ion and pH effects in the nanoenvironment of ligand-free metal nanoparticles,. Engineering in life sciences: Industry, Environment, Plant, Food, Vol. Strategies to harvest the unique properties of laser-generated nanomaterials in biomedical and energy applications,.
Structure of biocompatible coatings produced from hydroxyapatite nanoparticles by detonation spraying,. Freyer, Katja; Asikainen, Mervi A. Asikainen; Hirvonen, Pekka E. Study and assessment of microbial communities in natural and commercial bioleaching systems,. Sulfate radical-based water treatment in presence of chloride: Formation of chlorate, inter-conversion of sulfate radicals into hydroxyl radicals and influence of bicarbonate,.
Supporting of ligand-free gold nanoparticles on titania and its catalytic activity in liquid-phase oxidation of ethanol,. Synthesis and X-ray crystal structure of diimidosulfinate transition metal complexes,. Trans Tech Publications, - Solid state phenomena; , pp. Synthesis, characterization and in vitro effects of 7 nm alloyed silver-gold nanoparticles,.
Synthesis, morphology and structure of the dense Y1-xEux 2O3 spherical shape particles,. Synthesis of heterobimetallic group 13 compounds via oxidative addition reaction of gallanediyl LGa and InEt3,. Synthesis of metal atom clusters by pulsed laser fragmentation in liquid and investigation of their ripening dynamics,. Synthetic receptors for biomolecules: Lee, Sanghun; Flores, Susana M.
Temperature dependence of surface reorganization characteristics of amphiphilic block copolymer in air and in water studied by scanning force microscopy,. The effect of functionalized gold nanoparticles on pathologically aggregating proteins,. The effect of patterned titanium substrates on the properties of silver-doped hydroxyapatite coatings,. Herzog, Gal; Shmueli, Merav D. The lys-specific molecular tweezer, CLR01, modulates aggregation of the mutant p53 DNA binding domain and inhibits its toxicity,. Thin-film composite membranes for organophilic nanofiltration based on photo-cross-linkable polyimide,.
Tuning the photonic properties of chiral nematic mesoporous organosilica with hydrogen-bonded liquid-crystalline assemblies,. Journal of Materials Chemistry, C: Materials for Optical and Electronic Devices, Vol. Two step and one step preparation of porous nanocomposite cellulose membranes doped with TiO2,. Springer, - Springer Proceedings in Physics; , Vol. Melnikov, Alexey; Alekhin, A. Ultrafast non-local spin dynamics in metallic bi-layers by linear and non-linear magneto-optics,.
Springer, - Springer Proceedings in Physics; , pp. Ultrafiltration membranes with markedly different pH- and ion-responsivity by photografted zwitterionic polysulfobetain or polycarbobetain,. Universal route to polycyclic aromatic hydrocarbon analysis in foodstuff: Zhang, Ruyjong; Neu, Thomas R. Use of lectins to in situ visualize glycoconjugates of extracellular polymeric substances in acidophilic archaeal biofilms,.
Wet-chemical synthesis of different bismuth telluride nanoparticles using metal organic precursors: Zwischenbilanz der fachdidaktischen Arbeit im Fach Chemie und im Bereich des naturwissenschaftlich-experimentellen Arbeitens,. Jendrzej, Sandra; Oberhofer, F. Accumulation of iodine radiolabel by highly pure, laser-generated chemisorbant nanoparticles for medical application,.
Adsorption of colloidal platinum nanoparticles to supports: Affinity polymers tailored for the protein A binding site of immunoglobulin G proteins,. Alloying colloidal silver nanoparticles with gold disproportionally controls antibacterial and toxic effects,. Amplified additive manufacturing by gold nanoparticles during laser sintering of semiconductors,. A novel high-temperature combustion based system for stable isotope analysis of dissolved organic carbon in aqueous samples. Cox's Bazar; Bangladesh; 21 October through 23 October - , - , Article number A pH-sensitive poly methyl methacrylate copolymer for efficient drug and gene delivery across the cell membrane,.
Million, Nina; Nachev-Wilke, P. Aqueous polymer-capsules around laser generated nanoparticles for burn wound treatment,. Artificial oxygen carriers based on perfluorodecalin-filled poly n-butyl-cyanoacrylate nanocapsules,. European Science Education Research Association, , pp.
International journal of science and mathematics education: A study of photothermal laser ablation of various polymers on microsecond time scales,. Eine problemorientierte Experimentierbox zum Thema Neutralisation in zwei verschiedenen Kontexten. Naturwissenschaftliche Bildung zwischen Science- und Fachunterricht: Advanced Biomaterials and Devices in Medicine, Vol. Biocompatible gold submicrometer spheres with variable surface texture fabricated by pulsed laser melting in liquid,. Biofilm formation, communication and interactions of leaching bacteria during colonization of pyrite and sulfur surfaces,.
Calcium phosphate increases the encapsulation efficiency of hydrophilic drugs proteins, nucleic acids into poly D,L-lactide-co-glycolide acid nanoparticles for intracellular delivery,.
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Calcium phosphate nanoparticles show an effective activation of the innate immune response in vitro and in vivo after functionalization with flagellin,. Carbohydrate metabolism in archaea: Current insights into unusual enzymes and pathways and their regulation,. Carbon isotope ratio analysis of steroids by high temperature liquid chromatography - isotope ratio mass spectrometry,. Characterization of a phosphotriesterase-like lactonase from the hyperthermoacidophilic crenarchaeon Vulcanisaeta moutnovskia,.
Characterization of exopolymeric substances EPS produced by Aeromonas hydrophila under reducing conditions,. Charakterisierung und Strukturierung von Kontexten im naturwissen-schaftlichen Unterricht: Vorschlag einer theoretischen Modellierung,. Charge and ligand effects on Au and Pt nanoparticle electrodeposition for medical application,. The journal of physical chemistry. Colonization and biofilm formation of the extremely acidophilic archaeon Ferroplasma acidiphilum,. Fissan, Heinz; Ristig, S. Ahlberg, Sebastian; Meinke, Martina C.
Comparison of silver nanoparticles stored under air or argon with respect to the induction of intracellular free radicals and toxic effects toward keratinocytes,. European journal of pharmaceutics and biopharmaceutics: Concentration driven phase transitions in multiphase porous media with application to methane oxidation in landfill cover layers,.
Control of oil-wetting on technical textiles by means of photo-chemical surface modification and its relevance to the performance of compressed air filters,. The role of carbonaceous deposits in the activity and stability of Ni-based catalysts applied in the dry reforming of methane,. Counting of oxygen defects versus metal surface sites in methanol synthesis catalysts by different probe molecules,.
Angewandte Chemie international edition, Vol. Cu-based catalyst resulting from a Cu,Zn,Al hydrotalcite-like compound: Current state of laser synthesis of metal and alloy nanoparticles as ligand-free reference materials for nano-toxicological assays,. Current state on laser synthesis of metal and alloy nanoparticles, qualified as ligand-free reference materials for nano-toxicological assays,.
Design of bivalent gold nanoparticle-oligonucleotide-peptide conjugates for duplex and triplex hybridization,. Development of a Pedagogical Content Knowledge test of chemistry language and models,. Springer Fachmedien Wiesbaden, - Jahrbuch Grundschulforschung; 17 , pp. Dose-dependent surface endothelialization and biocompatibility of polyurethane noble metal nanocomposites,. Dynamic surface processes of nanostructured Pd2Ga catalysts derived from hydrotalcite-like precursors,.
Effects of silver nitrate and silver nanoparticles on a planktonic community: Klinische Monatsblatter fur Augenheilkunde, Vol. Electrophoretic deposition of ligand-free nanoparticles for the generation of nanostructures on 3D-medical implants,. Pires; Leal, Joao Paulo,. Enthalpies of formation of europium alkoxides: Evaluation of pulsed laser ablation in liquids generated gold nanoparticles as novel transfection tools: Frontiers in Ultrafast Optics: Environmental Progress and Sustainable Energy, Vol.
Fabrication, ultra-structure characterization and in vitro studies of RF magnetron sputter deposited nano-hydroxyapatite thin films for biomedical applications,. Femtogram detection of cytokines in a direct dot-blot assay using SERS microspectroscopy and hydrophilically stabilized Au-Ag nanoshells,. Few-cycle laser pulse induced plasmon assisted thermionic injection in metal-insulator-metal junctions,.
Flame-retardant finishing of cotton fabrics using polyamino carboxylic acids and sodium hypophosphite,. Formation of bromate in sulfate radical based oxidation: Mechanistic aspects and suppression by dissolved organic matter,. Policy, Research and Practice: Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, Vol. Streich, Carmen; Krause, L. Functionalized gold nanoparticles as analytical tools for protein conformational disorders,.
Journal of Materials Engineering and Performance, Vol. Macromolecular Materials and Engineering, Vol. Gold and silver nanoparticle monomers are non-SERS-active: A negative experimental study with silica-encapsulated Raman-reporter-coated metal colloids,. Growth of the acidophilic iron—sulfur bacterium Acidithiobacillus ferrooxidans under Mars-like geochemical conditions,.
Angewandte Chemie International edition, Vol. Impact of biofilm accumulation on transmembrane and feed channel pressure drop: Impact of Desulfovibrio alaskensis biofilms on corrosion behaviour of carbon steel in marine environment,. Colloidal nanoparticles for biomedical applications IX: Improvement and evaluation of a laboratory work for first-semester teacher-students,. Influence of different nano-structured surface topographies on electrode impedance [Poster],. Proceedings BMT , Influence of ligands on the electrophoretic deposition of nanoparticles on surfaces,.
Influence of ligands on themobility of nanoparticles during the electrophoretic deposition,. Fundamentals and Applications; October , , Hernstein - Injection of ligand-free gold and silver nanoparticles into murine embryos does not impact pre-implantation development,. Million, Nina; Nachev, P. In-situ conjugation of nanoparticles using ultrahort pulsed laser ablation in monomer solutions for electrospinning on burn wounds: In situ non-DLVO stabilization of surfactant-free, plasmonic gold nanoparticles: In-situ-Untersuchung der Transfektion mit Calciumphosphat- Nanopartikeln durch time-lapse microscopy,.
Integration lasergenerierter Nanomaterialien in Medizinprodukten und Katalysatoren,. Integration of magnetic, plasmonic, and catalytic colloidal nanoparticle building blocks into biomedical and catalysis supports,. Interaction of colloidal nanoparticles with their local environment: Gamrad, Lisa; Mancini, R. Interference and binding of gold nanoparticle conjugates with Y-Chromosome bearing Spermatozoa,. In-tube extraction-GC-MS as a high-capacity enrichment technique for the analysis of alcoholic beverages,.
Investigation of coking during dry reforming of methane by means of thermogravimetry,. Investigation of the malE promoter and MalR, a positive regulator of the maltose regulon, for an improved expression system in Sulfolobus acidocaldarius,. Investigation of the morphology and elemental composition of the silicon-containing calcium phosphate coating treated by intensive pulsed electron beam,. Cox's Bazar; Bangladesh; 21 October through 23 October - , , Article number In vitro and in vivo interactions of selected nanoparticles with rodent serum proteins and their consequences in biokinetics,.
Ion mobility and clustering of sodium hydroxybenzoates in aqueous solutions: A molecular dynamics simulation study,. Krawinkel, Judith; Richter, U. Laser based intracellular drug delivery with endocytozed peptide-conjugated gold nanoparticles,. Laser fragmentation and mass-specific energy balancing in a free liquid jet for fragmentation threshold determination,. Laser generated bioactive nanoparticles in aqueous polymer-capsules for burn wound therapy,.
John Wiley and Sons, Inc, , pp. LDH-derived Ni-catalysts in dry reforming of methane at high temperatures for an efficient CO2-conversion into syngas: Ligand-free gold atom clusters adsorbed on graphene nano sheets generated by oxidative laser fragmentation in water,. Ligand-free nanoparticles by laser ablation in liquids for biomedical and energy application,.
Waxmann, - Fachdidaktische Forschungen; 6 , pp. Low fouling negatively charged hybrid ultrafiltration membranes for protein separation from sulfonated poly arylene ether sulfone block copolymer and functionalized multiwalled carbon nanotubes,. Macroinitiator-mediated photoreactive coating of membrane surfaces with antifouling hydrogel layers,. Magnesiothermic conversion of the silicamineralizing golden algae Mallomonas caudata and Synura petersenii to elemental silicon with high geometric precision,.
Journal of materials chemistry. B, Materials for biology and medicine, Vol. Manipulation of pyrite colonization and leaching by iron-oxidizing Acidithiobacillus species,.