Dissertations / Theses on the topic 'Significant molecules'
To see the other types of publications on this topic, follow the link: Significant molecules.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Significant molecules.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Peppe, Salvatore. "Some unusual, astronomically significant organic molecules." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09php4241.pdf.
Full textAbstract:
Appendix inside back cover. "June 2002" Bibliography: leaves 157-168. Experimental and theoretical studies were carried out on a number of unusual organic molecules of potential astronomical significance. The experimental work was corroborated by various theoretical approaches and by utilising computer-based quantum chemical calculations. Various covalently bound, anionic and neutral oxocarbon species were formed and studied. Additionally, two analogous heterocumulenic systems were investigated. Some isomers of either system, when energised, were shown to undergo gas-phase rearrangement processes.
2
Morisawa, Yusuke. "Spectroscopic study of some chemically significant molecules in molecular clouds." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144599.
Full text
3
Ray, Samapika. "Study to explore inclusion complexations and assorted interactions of some industrially and biologically significant molecules in diverse systems." Thesis, University of North Bengal, 2022. http://ir.nbu.ac.in/handle/123456789/4789.
Full text
4
Barman, Siti. "Investigation on solvation behaviour and host guest inclusion complexes of some significant molecules with diverse cyclic compounds." Thesis, University of North Bengal, 2017. http://ir.nbu.ac.in/handle/123456789/2588.
Full text
5
Dutta, Ashutosh. "Exploration of diversified interactions of some significant compounds prevalent in several environments by physicochemical contrivance." Thesis, University of North Bengal, 2018. http://ir.nbu.ac.in/handle/123456789/2787.
Full text
6
Day, G. M., T. G. Cooper, A. Cruz-Cabeza, K. E. Hejczyk, H. L. Ammon, S. X. M. Boerrigter, J. S. Tan, et al. "Significant progress in predicting the crystal structures of small organic molecules ¿ a report on the fourth blind test." International Union of Crystallography, 2009. http://hdl.handle.net/10454/4748.
Full textAbstract:
noWe report on the organization and outcome of the fourth blind test of crystal structure prediction, an international collaborative project organized to evaluate the present state in computational methods of predicting the crystal structures of small organic molecules. There were 14 research groups which took part, using a variety of methods to generate and rank the most likely crystal structures for four target systems: three single-component crystal structures and a 1:1 cocrystal. Participants were challenged to predict the crystal structures of the four systems, given only their molecular diagrams, while the recently determined but as-yet unpublished crystal structures were withheld by an independent referee. Three predictions were allowed for each system. The results demonstrate a dramatic improvement in rates of success over previous blind tests; in total, there were 13 successful predictions and, for each of the four targets, at least two groups correctly predicted the observed crystal structure. The successes include one participating group who correctly predicted all four crystal structures as their first ranked choice, albeit at a considerable computational expense. The results reflect important improvements in modelling methods and suggest that, at least for the small and fairly rigid types of molecules included in this blind test, such calculations can be constructively applied to help understand crystallization and polymorphism of organic molecules.
7
Campanher, Carlos Henrique. "A aprendizagem significativa crítica aplicada ao ensino da constante de Avogadro e o Mol." Universidade Federal do Pampa, 2016. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/1038.
Full textAbstract:
Submitted by Andrea Pereira (andrea.pereira@unipampa.edu.br) on 2017-02-13T12:17:05Z
No. of bitstreams: 2
license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5)
FUNDAÇÃO UNIVERSIDADE FEDERAL DO PAMPA.pdf: 3463256 bytes, checksum: 358c02be565099362f593708f371d18b (MD5)Approved for entry into archive by Vanessa Dias (vanessa.dias@unipampa.edu.br) on 2017-02-14T13:27:39Z (GMT) No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) FUNDAÇÃO UNIVERSIDADE FEDERAL DO PAMPA.pdf: 3463256 bytes, checksum: 358c02be565099362f593708f371d18b (MD5)
Made available in DSpace on 2017-02-14T13:27:39Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) FUNDAÇÃO UNIVERSIDADE FEDERAL DO PAMPA.pdf: 3463256 bytes, checksum: 358c02be565099362f593708f371d18b (MD5) Previous issue date: 2016-02-24
O presente trabalho foi elaborado com o objetivo de abordar o ensino da Constante de Avogadro e o número de moléculas, tendo como desafio, contextualizar o ensino da estequiometria, de uma forma que seja significativa. Partindo do princípio que o ensino através de metodologias tradicionais, com um alto número de aulas expositivas e com programas curriculares totalmente conteudistas, causam a desmotivação dos alunos. Estes são aspectos que tornam o processo de ensino - aprendizagem de Química menos interessante, desmotivando o aluno. Como uma proposta, que possa vir a contribuir com uma mudança de rota, a aprendizagem significativa crítica, apresenta-se como uma nova prática de ensino da estequiometria. Os procedimentos didáticos utilizados visam promover a reflexão sobre problemas contemporâneos do aluno e contribuir para a reflexão, do estudante no processo de ensino/aprendizagem da Química e a formação de um indivíduo crítico. A aplicação da proposta foi realizada com uma turma de 2º ano do Ensino Médio de uma escola da rede estadual de ensino, localizado no município de Santiago, no estado do Rio Grande do Sul, na Região Sul do Brasil, durante os meses de março, abril e maio de 2014. A investigação consistiu em efetivar uma prática considerada diferenciada para aquela realidade escolar que pudesse contribuir para a melhoria do ensino/aprendizagem de Química e para a eficácia de metodologias variadas através da elaboração de um material didático mediado pelo uso da pesquisa, com a construção de mapas conceituais, seminários, vídeos, aulas práticas não convencionais e a interlocução professor - aluno. Embasando esta proposta, a teoria da aprendizagem significativa e a teoria da aprendizagem significativa crítica de Ausubel e Moreira respectivamente. A análise da pesquisa foi feita a partir dos resultados obtidos com a aplicação destas metodologias em uma das turmas e sua comparação com os resultados obtidos em outra turma na qual não foram implementadas as metodologias. Os alunos que participaram desta proposta, mostraram um interesse maior na aprendizagem, obtendo um aproveitamento maior em relação a qualidade do material produzido. A aprendizagem de forma significativa crítica, trouxe uma vontade maior de aprender por parte do aluno do que a metodologia clássica.
This work was done in order to address the teaching of the Avogadro constant and the number of molecules, with the challenge to contextualize the teaching of stoichiometry, in a way that is meaningful. Assuming that teaching through traditional methods, with a high number of lectures and fully conteudistas curricula, cause demotivation of students. These are aspects make the teaching process - Chemistry learning less interesting, discouraging the student. As a proposal, which may contribute to a change of route, the significant critical learning, it presents itself as a new teaching practice stoichiometry. Didactic procedures used aim to promote reflection on contemporary student problems and contribute to the reflection, the student in the teaching / learning of chemistry and the formation of a critical individual. The implementation of the proposal was held with a group of 2nd year of high school a school state schools located in the city of Santiago, in the state of Rio Grande do Sul, in southern Brazil, during the months of March, April and May 2014. the investigation was to carry out a considered differentiated practice for that school reality that could contribute to the improvement of the teaching / learning of chemistry and the effectiveness of different methodologies by developing educational material mediated by the use of search with the construction of concept maps, seminars, videos, unconventional practical classes and teacher dialogue - student. Basing this proposal, the theory of meaningful learning and critical theory of meaningful learning of Ausubel and Moreira respectively. The analysis of the research was done from the results obtained from the application of these methodologies in one of the classes and their comparison with the results obtained in another class in which the methods were not implemented. Students, who participated in this proposal, have shown greater interest in learning, getting better use in relation to quality of material produced. Learning significant critically, brought a greater desire to learn from the student than the classical methodology.
8
Muneer, Saiqa. "Novel nanoformulations and nanosensors for bioactive molecules of biomedical significance." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213224/1/Saiqa_Muneer_Thesis.pdf.
Full textAbstract:
This thesis demonstrates novel nanosensors and nanomaterials for the sensitive detection of bioactive molecules (antibody therapeutics and antibiotics) in complex biological matrices utilizing thiol chemistry for label-free SERS detection. In addition to biomedical analysis, formulation development of dry powder inhalers overcomes the issues of adverse effects associated with parenteral or oral route of drug administration. It is expected to accomplish the key requisites like aerosolization properties, physicochemical characteristics, biocompatibility, and biodegradation with minimal side effects. Therefore, this study provided a motivation to address current advancement of detection techniques and development of novel drug delivery systems for the bioactive molecules.
9
Tascilar, Metin. "Clinical significance of molecular markers in pancreatic cancer." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/61858.
Full text
10
ZHANG, XIN. "Surface functionalization of bioactive glasses with natural molecules of biological significance." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2535899.
Full textAbstract:
Natural or artificial materials used for replacement or supplement the functions of living tissues, termed as biomaterials, may be bioinert (i.e. alumina and zorconia,) resorbable (i.e. tricalcium phosphate), bioactive (i.e. hydroxyapatite, bioactive glasses, and glass-ceramics) or porous for tissue ingrowth (i.e. hydroxyapatite-coated metals). Among all the biomaterials, bioactive glass and glass-ceramics are widely used in orthopedic and dental applications and are being developed for tissue engineering. However, to a large extent, the behavior and overall performance of biomaterials are governed by surface properties. Surface modifications therefore provide unique possibilities to control the subsequent surface interaction and response which are required for particular application. By tailoring the material surface, a wide portfolio of additional functionalities is enabled to overcome material deficiencies while maintaining its bulk material properties. As a consequence, the surface functionalization of materials has become pivotal for academic research as well as industrial product development.
Plant-derived polyphenols are compounds possessing one or more aromatic rings with one or more hydroxyl groups. They are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants, with more than 8,000 phenolic structures currently known, ranging from simple molecules such as phenolic acids to highly polymerized substances such as tannins. Numerous researches and investigation reported the notable biological activities of polyphenol, such as cardiovascular protection, cancer prevention and treatment, antiaging activity as well as applications in Alzheimer’s disease, oral health, immune function diabetes and other neurodegenerative disorders.
Till now, a number of previous investigations provide a number of surface functionalization techniques and make it possible to graft various kinds of biomolecules such as proteins, growth factors and enzymes to the surface of bioactive glass and glass-ceramics. However, very few researches have been focused on the coupling of natural bioactive polyphenols on surface of bioactive glass and glass-ceramics.
As a conclusion, the aim of this thesis is to combine bioactive glasses and glass-ceramics with natural polyphenols, in this case they are grape polyphenol and tea polyphenol extracted from grape skin and green tea respectively, in order to make it possible to immobilize biomolecules as well as prepare smart biomaterials with both typical inorganic activity and specific biological benefits from natural molecule.
This thesis can be divided into five chapters. The first chapter introduces the composition, chemical structure, biological properties and potential applications of plant polyphenols. In chapter II, the extraction methods and analysis techniques involved in polyphenol investigation are reviewed. Chapter III mainly illustrated the structure, property and biomedical application of biomaterials as well as methodologies and evaluation of surface functionalization. Materials and techniques related to this thesis are demonstrated in chapter IV. The last chapter, also the core chapter of this thesis, describes the results and discussions in five separate sections: i) surface functionalization of SCNA and CEL2 with gallic acid; ii) surface functionalization of SCNA and CEL2 with polyphenol extracted from grape skin; iii) surface functionalization of SCNA and CEL2 with polyphenol extracted from green tea; iv) surface functionalization of SC-45 with gallic acid and buffered gallic acid and v) surface functionalization of SC-45 with folic acid.
11
Agarwalla, H. "Design and synthesis of molecular probes for biological and environmental significant ions." Thesis(Ph.D.), CSIR- National Chemical Laboratory, Pune, 2016. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2246.
Full text
12
Lapthorn, Cristian Lewis. "The application of ion mobility mass spectrometry to molecules of pharmaceutical significance." Thesis, University of Greenwich, 2016. http://gala.gre.ac.uk/18125/.
Full textAbstract:
Ion mobility-mass spectrometry experiments have been conducted to measure the drift-time and calculate collision cross-sections (CCSs) using travelling wave ion mobility spectrometry, and determine the CCS using drift-tube ion mobility spectrometry systems of analytes. The aim of the study was to identify if predictive approaches could facilitate rapid and definitive assignment of charge location sites and chemical structure. Molecular modelling was conducted to determine the energy minimised/geometry optimised structures and charge distribution of the protonated molecules studied. The geometry and charge distribution data were utilised in subsequent ion mobility calculations using two main methods 1) projection approximation and 2) trajectory method. Fluoroquinolone antibiotics were investigated as previous literature had postulated the ion mobility separation of charge location isomers differing only by their protonation site with little expected difference in their geometry (see Chapter 2). Projection approximation prediction of theoretical CCSs (tCCSs) for the singly protonated molecules of norfloxacin (with the proton assigned to all possible oxygen or nitrogen-containing protonation sites to generate candidates) revealed < 2 Å2 difference in tCCSs based on molecular modelling. In stark contrast the experimental CCS (eCCS) demonstrated > 10 Å2 difference between different components. The product ion spectra are consistent with the hypothesis of charge location isomer mobility separated components. Investigations with other fluoroquinolones, with both drift-tube ion mobility and travelling wave ion mobility, and using the trajectory method, remain consistent with the hypothesis of charge location isomers (see Chapter 3). A larger scale study sought to probe the accuracy of tCCSs over a large number of small molecule drug structures. If tCCSs accurately predict eCCSs, then tCCSs could be used to identify compounds and isomers based on their CCSs (see Chapter 4). Finally, software was developed to considerably accelerate the calculation of trajectory method tCCSs from 8-100 times faster than existing published approaches depending on available computing infrastructure (see Chapter 5). In summary this research project has explored whether eCCSs and tCCSs may be useful as a key structural tool alongside other traditional measurements including chromatographic retention time and m/z.
13
Hardingham, Jennifer E. "Molecular detection and significance of circulating colorectal cancer cells /." Title page, table of contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phh264.pdf.
Full text
14
Sarinas, Simon. "Application of Fourier Transform Raman Spectroscopy to the characterisation of significant biological materials." Thesis, Queensland University of Technology, 1994. https://eprints.qut.edu.au/37167/1/37167_Sarinas_1994.pdf.
Full textAbstract:
Raman spectroscopy has experienced a true "renaissance" since the development of Fourier Transform Raman instrumentation. The objective of this thesis is to illustrate the versatility of FT-Raman spectroscopy for the investigation and characterisation of biological molecules and systems. In addition to the positive attributes possessed by FT-Raman spectroscopy for such analysis, inherent shortcomings of the technique are discussed. This report serves as a concise reference for any researcher or analytical scientist considering FT-Raman spectroscopy for the analysis of biomolecular systems.
15
Day, Richard Michael. "Study of the pathogenic significance of epithelial cell adhesion molecules in inflammatory bowel disease." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286598.
Full text
16
Ali, Hamid Raza. "Molecular classification of breast cancer : histology-based assays and clinical significance." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607764.
Full text
17
Anjomshoaa, Ahmad, and n/a. "Prognostic significance of a gene proliferation signature in colorectal cancer." University of Otago. Department of Biochemistry, 2007. http://adt.otago.ac.nz./public/adt-NZDU20071218.134516.
Full textAbstract:
Aberrant cell proliferation is a fundamental feature of cancer. It is thus not unexpected that many studies have been devoted to the exploration of tumour cell proliferation as a potential indicator of outcome. Indeed, in most malignancies, high expression of proliferation markers and more accurately, increased expression of proliferation-related genes have been strongly associated with poor outcome. In colorectal cancer (CRC), however, discordant results have been reported and the prognostic significance of cell proliferation has not been demonstrated in this type of cancer. As these results were mostly based on the subjective assessment of a single proliferation marker, this work set out to evaluate the association between the proliferative activity of CRCs and their malignant potential using an objective microarray-based multi-gene proliferation signature.
In the first step, a gene proliferation signature (GPS) was derived from analysis of a CRC cell line model. Ten CRC cell lines were harvested under semi- and fully-confluent conditions to obtain RNA from two stages that differed in their proliferative activity. Gene expression profiles of the two growth stages were analyzed on oligonucleotide arrays and a GPS was identified by gene ontology analysis of differentially expressed genes. In the second step, the performance of the signature to classify patients into prognostic groups was examined using two independent cohorts of primary CRC tumours (cohort A: 73 tumours in stages I-IV, cohort B: 55 tumours in stages I-II). Further, the signature was applied to a population of liver metastases to establish its association with the malignant potential of CRC. Finally, the capacity of the signature to detect clinically distinct CRC populations was compared with that of the proliferation marker Ki-67 in a classic immunohistochemical approach.
The GPS consisted of 38 mitotic cell cycle genes, which were over-expressed in actively cycling cells relative to growth-inhibited cells in vitro. Intriguingly, a reduced GPS expression was associated with (i) the presence of lymph node or distant metastasis in cohort A, (ii) an increased risk of recurrence, and (iii) shorter overall and recurrence-free survival in both cohorts of primary CRCs (p<0.05). While the association between the GPS and clinical outcome was not independent of the disease stage in cohort A, reduced GPS expression was an independent predictor of outcome in cohort B. Importantly, adjuvant therapy had no impact on this association. Furthermore, GPS expression was reduced in CRC liver metastases, confirming that decreased proliferation is an indicator of the malignant potential in CRC. While reduced proliferation in liver metastases was also observed by Ki-67 immunostaining, the classic proliferation marker was not able to stratify primary CRCs into different prognostic groups.
To the best of our knowledge, this study is the first to report an association between the reduced expression of a multi-gene proliferation signature and poor outcome in cancer. This finding contradicts the long-held belief that increased proliferation is an indicator of tumour malignancy. In contrast to many other cancers, reduced proliferation appears to be a significant component of a biological signature associated with malignant potential of CRC tumours. Investigating the reasons why CRC differs from other cancer types may provide insights into important underlying biological mechanisms. If this association can be verified in larger cohorts, the GPS may have important clinical implication for identification of high-risk early stage CRC patients.
18
Silva, Carolina de Barros Machado da. "Filogenia molecular e filogeografia do gênero Salminus (Characiformes)." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/9371.
Full textAbstract:
Submitted by Aelson Maciera (aelsoncm@terra.com.br) on 2018-02-01T16:44:30Z
No. of bitstreams: 1
TeseCBMS.pdf: 4190969 bytes, checksum: 7f39aaee9acdf743fad7b9fcaec22326 (MD5)Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-02-01T18:49:59Z (GMT) No. of bitstreams: 1 TeseCBMS.pdf: 4190969 bytes, checksum: 7f39aaee9acdf743fad7b9fcaec22326 (MD5)
Approved for entry into archive by Ronildo Prado (bco.producao.intelectual@gmail.com) on 2018-02-01T18:50:08Z (GMT) No. of bitstreams: 1 TeseCBMS.pdf: 4190969 bytes, checksum: 7f39aaee9acdf743fad7b9fcaec22326 (MD5)
Made available in DSpace on 2018-02-01T18:54:28Z (GMT). No. of bitstreams: 1 TeseCBMS.pdf: 4190969 bytes, checksum: 7f39aaee9acdf743fad7b9fcaec22326 (MD5) Previous issue date: 2016-09-30
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Salminus is a genus comprised of four Neotropical medium- and large-sized fishes species, top predators, with both recreational and commercial importance. The paucity of information on taxonomy, phylogeny and phylogeography make appropriate conservation policies difficult for the genus, which is in a significant population decline. For this reason, our goal was, by using mitochondrial (COI, Cytb and D-loop) and nuclear (RAG2 and S7 intron) molecular makers, to elucidate taxonomic uncertainties, identify cryptic diversity, investigate the phylogenetic relationship among the species and infer the historical processes that shaped the current Salminus distribution. To assist in taxonomic issues, we employed the traditional DNA barcoding and GMYC COI-based analyses in 110 specimens, representing the four valid species. In both methodologies, eight MOTUs (molecular operational taxonomic units) were identified. Only two species, Salminus affinis and Salminus franciscanus, represented a MOTU each. The species Salminus brasiliensis and Salminus hilarii were represented by two and four MOTU, respectively. These MOTUs are distributed in distinct hydrographic basins where morphological polymorphisms had already been described. The average intraspecific distances greater than the optimal threshold of 1.1% (S. brasiliensis – 3.6%, e S. hilarii – 5%), reinforce the idea of more taxonomic units in Salminus. The multiloci analysis recovered interesting information about the cryptic diversity: the paraphyletic mitochondrial lineages of S. brasiliensis, one from Upper Paraná river and another composed of specimens from the other regions of the Platina basin, formed a unique monophyletic group. For S. hilarii, despite the four MOTUs observed, only three of them were recovered. Therefore, based on multiloci analysis and phylogenetic species concept, we proposed a new taxonomic scenario for Salminus. The genus is now composed of six species: S. affinis, S. franciscanus, S. brasiliensis, S. hilarii, Salminus sp. Amazonas and Salminus sp. Araguaia. The phylogeny reconstruction refuted hypotheses previously proposed. S. affinis, the only trans-Andean species, was the sister species of the other Salminus, which formed two main groups: Northwest group, composed of S. sp. Amazonas and S. sp. Araguaia, and Southeast group, formed by S. brasiliensis, S. franciscanus and S. hilarii. The divergence processes among Salminus began in Later Miocene and it is associated with vicariance and geodispersion events that shaped the hydrological landscape in the past 12 million years. For the first time, it was used a model-based approach in order to test alternative biogeographic scenarios and to distinguish phylogeography signatures among the events responsible for Neotropical fishes’ diversification. We evidenced that the distinct vicariance and geodispersion signatures could be detected in our biological model. A clear description of these species brings in a valuable information for conservation, because, now, six biological units need to be protected. As these species are located in distinct hydrographic basins, each basin becomes one important biogeographic unit to maintain the evolutionary and ecological processes that sustain the species permanence and diversity.
Salminus é um gênero constituído por quatro espécies de peixes Neotropicais de médio e grande porte, predadores topo de cadeia, que possuem importância na pesca comercial e esportiva. Escassez de informações quanto a taxonomia, filogenia e filogeografia, dificultam medidas de conservações adequadas para o gênero, que se encontra em acentuado declínio populacional. Por essa razão, este estudo objetivou, através do emprego de marcadores moleculares mitocondriais (COI, Cytb e D-loop) e nucleares (RAG2 e íntron do S7), elucidar incertezas taxonômicas, identificar diversidade críptica, investigar as relações filogenéticas entre as espécies e inferir os processos históricos que modelaram a distribuição atual do gênero Salminus. Para auxiliar nas questões taxonômicas, nós empregamos análise de DNA barcoding tradicional e GMYC utilizando o marcador COI em 110 espécimes, representando as quatros espécies válidas. Em ambas metodologias, oito MOTUs (unidades taxonômicas operacionais moleculares) foram identificadas. Apenas duas espécies, Salminus affinis e Salminus franciscanus, apresentaram uma única MOTU cada. As espécies Salminus brasiliensis e Salminus hilarii foram representadas por duas e quatro MOTUs, respectivamente. Essas MOTUs estão distribuídas em distintas bacias hidrográficas onde polimorfismos morfológicos já haviam sido descritos. As médias das distâncias intraespecíficas superiores ao threshold ótimo de 1.1% (S. brasiliensis – 3.6%, e S. hilarii – 5%), reforçam a ideia de mais unidades taxonômicas em Salminus. A análise multiloci recuperou informações interessantes quanto à diversidade críptica: as linhagens mitocondriais parafiléticas de S. brasiliensis, uma proveniente do Alto rio Paraná e outra formada por espécimes das demais regiões da bacia Platina, formaram um único grupo monofilético. Para S. hilarii, apesar de quatros MOTUs observadas, apenas três foram recuperadas. Portanto, baseada na análise multiloci e no conceito filogenético de espécie, propomos um novo cenário taxonômico para Salminus. O gênero passa a ser constituído por seis espécies: S. affinis, S. franciscanus, S. brasiliensis, S. hilarii, Salminus sp. Amazonas e Salminus sp. Araguaia. A filogenia recriada refutou hipóteses previamente propostas. S. affinis, única espécie transandina, foi a espécie-irmã dos demais Salminus, que formam dois grandes grupos: grupo Noroeste, constituído por S. sp. Amazonas e S. sp. Araguaia, e grupo Sudeste, composto por S. brasiliensis, S. franciscanus e S. hilarii. Os processos de divergência entre as espécies do gênero se iniciou no Mioceno Superior e está associada a eventos de vicariância e geodispersão que modelaram a paisagem hidrogeológica nos últimos 12 milhões de anos. Pela primeira vez, foi utilizado uma abordagem baseada em modelos para testar cenários biogeográficos alternativos e distinguir se existem assinaturas filogeográficas entre os eventos responsáveis pelo processo de diversificação de peixes Neotropicais. Nós evidenciamos que distintas assinaturas filogeográficas entre vicariância e geodispersão puderam ser detectadas em nosso modelo biológico. A clara designação das espécies por si só já acarreta em uma informação valiosa para conservação, afinal seis unidades biológicas precisam ser protegidas. Como essas espécies estão localizadas em distintas bacias hidrográficas, cada bacia passa ser avaliada como uma unidade biogeográfica importante para a manutenção dos processos evolutivos e ecológicos que sustentam a diversidade e permanência das espécies.
19
Wong, Hetty Ngan-Ha 1969. "Characterization and significance of calnexin phosphorylation in mammals and Schizosaccharomyces pombe." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36851.
Full textAbstract:
Alteration in protein folding and its subsequent trafficking has been increasingly recognized as the molecular basis of numerous diseases. Cells have acquired a quality control mechanism to ensure proper folding and assembly of proteins. Misfolded and unassembled proteins are recognized by the quality control machinery at the ER and are retained and subsequently targeted for degradation. Calnexin has been identified as one of the major constituents of the ER quality control machinery. Calnexin is a type I phosphoprotein of the ER membrane. The luminal domain of calnexin displays a lectin-like molecular chaperone activity that interacts transiently with nascent glycoproteins and promotes their efficient and productive folding. The cytosolic domain of calnexin is phosphorylated. A prolonged association of a secretion impaired alpha 1-antitrypsin mutant with phosphorylated calnexin has been observed. Phosphorylation of calnexin was also suggested to regulate the rate of protein transport out of the ER. Furthermore, a prolonged association of newly synthesized MHC class 1 heavy chains with calnexin was found in a B lymphoblastoid cell line transfected with HLA-B701 after incubation with the phosphatase inhibitor, cantharidin or okadaic acid. Hence, phosphorylation on the cytosolic domain of calnexin may provide a potential to communicate and regulate its intralumenal lectin-binding domain.In this study, we have identified the in vivo phosphorylation sites of calnexin in both cultured mammalian cells and the fission yeast, Schizosaccharomyces pombe. By mass spectral analyses, mammalian calnexin is in vivo phosphorylated on three invariant serine residues, two phosphorylation sites are within CK2 recognition motifs and one is within a protein kinase C and/or proline-directed kinase (PDK) phosphorylation motif. By site-directed mutagenesis study, S. pombe calnexin is in vivo serine phosphorylated within a PDK phosphorylation motif. We have also identified ERK-1 as a candidate kinase for mammalian calnexin phosphorylation. Furthermore, we have examined the significance of mammalian calnexin phosphorylation in vitro employing isolated canine pancreatic microsomes. We showed that calnexin interacts with ribosomes and the interaction is regulated by the calnexin phosphorylation. ERK-1 phosphorylated calnexin was shown to exert an enhanced interaction between calnexin and ribosomes. Hence, calnexin phosphorylation may increase the concentration of calnexin in the proximity of translocon and facilitate the translocation and folding of glycoproteins.
20
Cáceres, Aguilar Mario. "Inversiones Cromosómicas de Drosophila: Origen Molecular y Significado Evolutivo de su Tamaño." Doctoral thesis, Universitat Autònoma de Barcelona, 2000. http://hdl.handle.net/10803/3910.
Full text
21
Takada, Yoshinori. "Molecular elucidation of the physiological significance of Ca2+ channelsome in neuronal function." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202810.
Full text
22
Han, Wei 1964. "Molecular electrophysiology underlying repolarization in canine cardiac purkinje cells : characterization and significance." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82889.
Full textAbstract:
Cardiac Purkinje fibers (PFs) play a very important role in cardiac electrophysiology. They are crucial for assuring appropriate timing and sequence of ventricle contraction and play an important role in cardiac arrhythmogenesis, largely via abnormalities in repolarization. Little work has been done to define the molecular electrophysiology of cardiac Purkinje cells (PCs). The primary hypothesis of this thesis was that PCs have unique molecular determinants of repolarization. The specific objectives were to characterize the repolarizing currents in isolated canine PCs, to clarify the molecular basis for these currents and to study role of PC current remodeling in a cardiac disease state. To achieve these goals, we used approaches at three different levels: the cellular level (with microelectrode techniques), the ionic level (with whole-cell patch clamp techniques) and molecular level (with competitive RT-PCR, Western blot analysis and immunocytochemistry).We first optimized PC isolation techniques, which allowed us to characterize repolarizing currents and to visualize channel protein distribution by immunolocalization in cardiac PCs. We then characterized an important repolarizing current, the transient outward current (Ito) in canine PCs. We found that Purkinje Ito has some unique properties compared to those of atrial and ventricular Ito, suggesting a different molecular basis. We therefore characterized the expression of alpha-subunits encoding Ito-like currents and the K+-channel interacting protein 2 (KChIP2) beta-subunit. We demonstrated important differences in the expression of Kv3.4; encoding a TEA-sensitive Ito channel, and of KChIP2, that might play an important role in the specific molecular composition of Purkinje Ito. We also characterized another important repolarizing current, the delayed rectifier (IK) that had been reported to be absent or small in PCs. We found that I K· in PCs has properties typical of those observed in other regions of the heart; and IK channel subunits ERG, KvLQT1 and minK were more sparsely expressed in PCs than in ventricular muscle (VM), potentially explaining the tendency of PCs to generate arrhythmias due to abnormal repolarization. We also noted important differences in the expression of the Ca2+-channel subunits (Cav1.2, Cav3.1, 3.2 and 3.3), the Na+/Ca2+-exchanger subunit NCX1 and the hyperpolarization-activated channel subunits HCN1, 2 and 4. Studies in human PCs confirmed that some of the unique PC ionic properties observed in dogs are also present in man. Finally, we showed that an experimental cardiac disease paradigm (congestive heart failure) causes characteristic ionic remodeling in PCs that may explain their role in potentially lethal arrhythmias associated with heart failure.
Our findings support the hypothesis of a unique and important molecular basis for the control of repolarization in cardiac PCs.
23
Maran, Louise Helena Martins Maran [UNESP]. "Filogenia molecular de Mazama americana (Artiodactyla: Cervidae) como auxílio na resolução das incertezas taxonômicas." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/140141.
Full textAbstract:
Submitted by LOUISE HELENA MARTINS MARAN null (louise.maran@outlook.com) on 2016-06-28T16:37:01Z
No. of bitstreams: 1
Dissertação_Definitivo.pdf: 2004003 bytes, checksum: 2157b94fbd9ba1934694a695aea03633 (MD5)Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2016-06-29T18:55:46Z (GMT) No. of bitstreams: 1 maran_lhmm_me_jabo.pdf: 2004003 bytes, checksum: 2157b94fbd9ba1934694a695aea03633 (MD5)
Made available in DSpace on 2016-06-29T18:55:46Z (GMT). No. of bitstreams: 1 maran_lhmm_me_jabo.pdf: 2004003 bytes, checksum: 2157b94fbd9ba1934694a695aea03633 (MD5) Previous issue date: 2016-05-31
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Estudos recentes com a espécie Mazama americana apontam duas linhagens cromossômicas dentro deste possível complexo de espécies crípticas e entre elas verificou-se a existência de eficiente barreira reprodutiva por isolamento pós-zigótico. No entanto, o efeito das pequenas diferenças cromossômicas entre populações é ainda pouco esclarecido, não sendo claro se seriam polimorfismos intraespecíficos, diferenças subespecíficas ou específicas. Marcadores moleculares permitem investigar se ocorreu fluxo entre estas populações e se este fluxo ainda ocorre no presente, auxiliando na elucidação dos processos evolutivos que ocorreram na diferenciação cromossômica e qual o real efeito dessas variações no isolamento e especiação no táxon. Diante do exposto, o presente trabalho estudou as relações filogenéticas entre variantes cromossômicas, com alto número diplóide, de M. americana com o objetivo de compreender melhor a história evolutiva da espécie e verificar a existência de unidades evolutivamente significativas dentro deste complexo específico, contribuindo para o delineamento de programas de conservação da espécie. As relações filogenéticas da espécie foram examinadas utilizando genes mitocondriais (citocromo b, citocromo oxidade I, região controladora D-loop e NADH dehigrogenase subunit 5), com 44 indivíduos de veados-mateiro provenientes de diferentes localidades do Brasil. Os resultados encontrados não corroboram a existência de unidades evolutivamente significativas dentro do grupo amostrado. A topologia encontrada nas árvores filogenéticas não mostram agrupamentos por citótipos, mas sim uma polifilia dos clados das árvores filogenéticas.
Recent studies on the species Mazama americana point two chromosomal lineages within red brocket deer and among them there was the existence of effective reproductive barrier post-zygotic isolation. However, the effect of these small chromosomal differences between these populations is not clearly established, it is not clear whether they would be intraspecific polymorphisms, subspecific or specific diferences. The molecular markers allow to investigate if there was flows occurred between these populations and whether these flows still occur in the present, helping to unravel the evolutionary processes that have occurred on chromosome differentiation and what the actual effect of these changes in isolation and speciation in the taxon. Given the above, this research project studied the phylogenetic relationships among chromosomal variants of M. americana with the aim of elucidating the evolutionary history of the species and verify the existence of evolutionarily significant units within this particular complex, contributing to the design of programs conservation of the species. The phylogenetic relationships of the species were examined using mitochondrial genes (cytochrome-b, cytochrome oxidase I, control region D-loop and NADH dehidrogenase subunit 5), with 44 individuals of red brocket deer from different locations in Brazil. The results do not support the existence of distinct evolutionary units within the sampled groups. The topologies found in phylogenetic tree show no groupings cytotypes but a polyphyly of clades of the phylogenetic tree.
CNPq: 132063/2014-0
24
Lincoln, Sara Ann Lincoln Ph D. Massachusetts Institute of Technology. "Molecular studies of the sources and significance of archaeal lipids in the oceans." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84916.
Full textAbstract:
Thesis (Ph. D. in Geochemistry)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references.
Marine archaea are ubiquitous and abundant in the modem oceans and have a geologic record extending >100 million years. However, factors influencing the populations of the major clades - chemolithoautotrophic Marine Group I Thaumarchaeota (MG-I) and heterotrophic Marine Group II Euryarchaeota (MG-II) - and their membrane lipid signatures are not well understood. Here, I paired techniques of organic geochemistry and molecular biology to explore the sources and significance of archaeal tetraether lipids in the marine water column. Using metagenomics, 16S rDNA pyrosequencing, QPCR and mass spectrometric analyses, I found that uncultivated MG-IL Euryarchaeota synthesize glycerol dialkyl glycerol tetraether (GDGT) lipids - including crenarchaeol, previously thought limited to autotrophic Thaumarchaeota. This finding has important implications for paleoenvironmental proxies reliant upon GDGTs. To investigate the effects of organic matter and bicarbonate + ammonia amendments on archaeal tetraether lipids and microbial community composition, I conducted large scale microcosm experiments. Experimental conditions did not promote the overall growth of archaea, but several changes in tetraether lipid abundance and relative ring distribution suggest that future incubation labeling studies using whole seawater may be valuable in probing the metabolism of individual archaeal clades in mixed populations. A rapid decrease in GDGT concentrations was observed within the first 44 h of the experiment, suggesting that the residence time of these compounds in the open ocean may be short. Changes in functional gene representation and microbial community composition over the course of the experiment provide potential insight into mechanisms of copiotrophy and the identity of bacteria that may degrade GDGTs. Finally, I present the results of a study of the sources and patterns of bacterial and archaeal GDGTs detected in the Lost City Hydrothermal Vent Field. Branched GDGTs, generally considered markers of terrestrial input to marine sediments, were detected in carbonate chimneys of this alkaline site near the mid-Atlantic Ridge. A relatively uncommon H-shaped GDGT was also present, and appears to be a marker of hydrothermal archaeal input rather than a mesophilic euryarchaeotal signal. Taken together, the work presented in this thesis emphasizes the necessity of understanding the biological underpinnings of archaeal lipids in the environment, increasingly used as biomarkers in microbial ecology and paleoenvironmental reconstruction.
by Sara Ann Lincoln.
Ph.D.in Geochemistry
25
Fiandalo, Michael Vincent. "PROTEASOME REGULATION OF CASPASE-8: SIGNIFICANCE IN CANCER." UKnowledge, 2012. http://uknowledge.uky.edu/biochem_etds/3.
Full textAbstract:
Anti-tumor therapeutic strategies based on combinations of chemotherapeutic agents with a death inducing ligand such as TNF-α Related Apoptosis Inducing Ligand (TRAIL), are directed towards selective and effective cancer cell apoptosis and enhanced therapeutic response. We previously demonstrated that proteasome inhibition sensitizes TRAIL resistant prostate cancer cells to TRAIL-mediated apoptosis via stabilization of the active p18 subunit of initiator caspase-8. The present study investigated the functional link between caspase-8 and the proteasome, by analyzing the impact of caspase-8 ubiquitination and proteasomal degradation on the outcomes of the extrinsic apoptosis pathway in cancer cells. Caspase-8 ubiquitination status was assessed by polyubiquitin immunoprecipitation (IP) and fluorescent microscopy. Apoptosis induction in response to death receptor stimuli or proteasome inhibitor was evaluated using the Annexin V/Propidium iodide staining (PI). To determine the consequences of proteasome inhibition on caspase-8 stability, trafficking, and activity following death receptor activation, we used the TRAIL-resistant human prostate cancer LNCaP cells, and the caspase-8 deficient Neuroblastoma 7 (NB7) cells, as cellular models for reconstituting the non-cleavable mutant forms of caspase-8. Our findings demonstrate that the non-cleavable forms of caspase-8 are capable of inducing apoptosis comparably to wild-type caspase-8 upon treatment with proteasome inhibitor and GST-TRAIL. Furthermore, caspase-8 processing into its active subunits preceded caspase-8 polyubiquitination, implicating caspase-8 processing as a potential regulatory mechanism, rather than a requirement for caspase-8 activation in apoptosis induction. The mechanistic control of caspase-8 by ubiquitination in cancer cells may have significant significance in bypassing mechanisms of therapeutic resistance in human tumors and optimization of anti-cancer treatment strategies in human tumors and optimization of anti-cancer treatment strategies.
26
Du, Shuhua. "Identification of the Functional Significance of a Novel Genetic Modifier of p53 – Ovca1." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1301528581.
Full text
27
Jurutka, Peter Wesley. "Characterization and evaluation of the functional significance of phosphorylation of the vitamin D receptor." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186336.
Full textAbstract:
The hormonal actions of 1,25-dihydroxyvitamin D3 (1,25(OH)₂D₃) are mediated by a nuclear 1,25(OH)₂D₃ receptor phosphoprotein (VDR). The phosphorylation of VDR was characterized in rat osteoblast-like cells (ROS 1712.S). In these bone cells, rat VDR (rVDR) was phosphorylated in the absence of the 1,25(OH)₂D₃ ligand and became hyperphosphorylated upon binding the sterol hormone or a novel, noncalcemic analog, 22-oxa-calcitriol. Treatment of ROS 17/2.S cells, transfected with a 1,25(OH)₂D₃-responsive reporter vector, with increasing concentrations of 1 ,25(OH)₂D₃ indicated a positive correlation between the level of receptor phosphorylation and rVDR transcriptional activity. Analysis of the deduced amino acid sequence of the rVDR and the human VDR (h VDR) revealed several consensus recognition sites for casein kinase II (CK-II), a nuclear-localized enzyme. Both of these receptors served as efficient substrates for CK-II, in vitro, in 1,25(OH)₂D₃ independent reactions. Evaluation of CK-IIcatalyzed phosphorylation of truncated and point-mutated human receptor species, in vitro, and of deletion and site-directed h VDR mutants in transfected ROS 17/2.8 and COS-7 cells revealed that a major site of CK-II phosphorylation is Ser208, a classic CK-II site located in the hormone binding domain of the receptor. The hVDR is also hyperphosphorylated at Ser208 in COS-7 cells overexpressing human CK-II. Replacement of Ser208 with either glycine or alanine does not disrupt the ability of h VDR to bind 1,25(OH)₂D₃, localize to the nucleus, associate specifically with the vitamin D responsive element (VDRE) or activate transcription. Significantly, phosphorylation of hVDR at the Ser208 target site by CK-II overexpressed in COS-7 cells stimulates 1,25(OH)₂D₃ mediated transcriptional activation of a reporter gene without affecting other receptor activities. Therefore, CK-II phosphorylation of h VDR appears to playa modulatory rather than obligatory role in receptor function. Conversely, protein kinase C (PK-C) phosphorylation ofhVDR at Ser51, located in the DNA binding domain, while also not required for receptor functions, results in an attenuation of VDRE binding. Finally, cAMP-dependent protein kinase (PK-A) phosphorylates h VDR in the "hinge" region of the receptor producing a decrease in 1,25(OH)₂D₃ stimulated gene activation. Thus, the hVDR appears to be a substrate for several protein kinases within distinct functional domains and the composite activity of the receptor may be dependent on the convergence of integrated inputs from several signal transduction pathways, including those involving CK-II, PK-C and PK-A. These results could explain how the transcriptional activity of VDR is governed during various stages of cell growth and differentiation as well as by "cross-talk" from other hormonal signals in specific vitamin D target organs.
28
Yamada, Ayako. "Dynamic self-organization of biomolecules in relation to their biological significance : single giant DNA and phospholipid molecules." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136864.
Full text
29
Kelley, Joanna L. "Adaptive evolution : from genome-wide scans to biological significance /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/10256.
Full text
30
Robinson, Jason M. "Functional Significance of mtDNA Cytosine Modification Tested by Genome Editing." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4561.
Full textAbstract:
The field of epigenetics is gaining popularity and speed, due in part to its capability to answer lingering questions about the root cause of certain diseases. Epigenetics plays a crucial role in regulation of the cell and cell survival, particularly by cytosine methylation. It remains controversial if DNMT’s which facilitate methylation are present in mammalian mitochondria and what the functional significance they may have on modification of mitochondrial DNA. CRISPR-Cas9 technology enabled genome editing to remove the MTS (mitochondrial targeting sequence) from DNMT1 of HCT116 cells, purposefully minimizing effects on nuclear cytosine methylation, while exclusively impacting mitochondrial modification. Removal of the DNMT1 MTS did not completely prevent the localization of this enzyme to the mitochondria according to immunoblot analysis. As well, deletion of the MTS in DNMT1 revealed only a small decline in transcription; not until removal of DNMT3B did we see a two-fold decrease in transcription from mitochondrial protein coding genes. No significant decline in transcription occurred when a DNMT3B knockout also lost the MTS of DNMT1; this study is evidencing that DNMT3B is possibly the more significant methyltransferase in the mitochondria. Our aim from this study and future research is to clearly characterize which enzymes in the mitochondria are controlling cytosine modifications and to understand the mechanistic complexities that accompany cause and consequence of epigenetic modifications.
31
Lin, Zhou. "Theoretical Studies on the Spectroscopy and Dynamics of Astrochemically Significant Species." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429633299.
Full text
32
Venn, Alexander Ashley. "Coral bleaching : the significance of the molecular diversity and photoprotective pigments of zooxanthellae (Symbiodinium)." Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423605.
Full text
33
Ho-Yen, Colan Maxwell. "The significance of c-Met in different molecular sub-types of invasive breast cancer." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8907.
Full textAbstract:
Introduction: Basal-like (BL) breast cancer is an aggressive sub-type of breast cancer for which there is no targeted systemic therapy. C-Met is a receptor tyrosine kinase implicated in breast cancer. Clinical trials assessing the efficacy of anti-c-Met therapy are underway, yet few studies have analysed the clinical significance of c-Met expression and/or activation in breast cancer, in particular whether there is a correlation with molecular sub-type. The aims of this study are: 1) to establish the clinical significance of c-Met expression in invasive breast cancer, 2) evaluate the novel proximity ligation assay (PLA) as a method of measuring c-Met activation and 3) address the effect of hepatocyte growth factor (HGF)-mediated c-Met phosphorylation on migration and protein expression in cell lines representative of the BL sub-type. Methods: Immunohistochemistry for c-Met was performed on 1455 cases of breast cancer using tissue microarray (TMA) technology. The PLA was performed on TMAs constructed from 181 breast cancers. C-Met expression and the PLA product were correlated with clinico-pathological parameters and survival. The effects of HGF on cell migration and protein expression were assessed using migration assays, western blots and immunofluorescent studies. Results: C-Met expression was independently associated with BL breast cancer (odds ratio = 6.44, 95% confidence interval (CI) = 1.74-23.78, p = 0.005) and reduced overall survival (hazard ratio = 1.81, 95% CI = 1.07-3.06), p = 0.026). The PLA signal was not associated with molecular sub-type or survival. HGF stimulation was associated with a significant increase in BL cell migration (p < 0.01) but no evidence of epithelial-mesenchymal transition was observed. Conclusion: My findings suggest BL breast cancer patients should be included in future trials of anti-c-Met therapy. Further work is necessary to establish the prognostic utility of the PLA as a measure of c-Met activation and the mechanisms driving HGF-mediated cell migration.
34
Lafleur, Christine. "The significance of enzyme 3-ß-hydroxysterol - delta24 reductase in cholesterol biosynthesis and steroidogenesis: an «in vitro» model to study Desmosterolosis." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67031.
Full textAbstract:
Desmosterolosis is an autosomal recessive condition in which affected individuals lack expression of the final enzyme in the cholesterol biosynthetic pathway, 3β-hydroxyΔ²4cholesterol reductase (DHCR24). The enzyme is responsible for converting desmosterol to cholesterol. It is characterized by several congenital abnormalities, as well as high circulating levels of desmosterol accompanied by hypocholesterolemia. This study was intended to examine the molecular disruptions involved in desmosterolosis and determine the potential impact on steroidogenesis using an in vitro approach. Due to the importance of cholesterol in cell-signaling and cell membrane integrity, it was found that desmosterol was a poor substitute for cholesterol in cell membranes. Cells deprived of cholesterol for 45 minutes rapidly underwent morphological changes and presumably became apoptotic. This effect was potentiated in cells with DHCR24 knock-down. Additionally, cells responded by increasing levels of cholesterol biosynthetic factors such as, SREBP1, SREBP2, SCAP, S1P, as well as the enzyme HMG Co A reductase all of which were measured using real-time PCR. The increase in these transcripts indicates that desmosterol cannot be sensed by the sterol sensing domain (SSD). Following cholesterol repletion, cells were able to restore a certain level normalcy in terms of morphology and the production of the transcripts listed above. Cholesterol is required for steroidogenesis in the adrenal cortex. We examined whether or not desmosterol could be used as a steroidogenic substrate. We measured levels of steroidogenic acute regulatory protein (StAR) as well as measured cortisol production with DHCR24 knock-down following cholesterol depletion and repletion with and without trophic stimulation. We found that in cells stimulated with vasoactive intestinal polypeptide, devoid of cholesterol and with endogenous synthesis impaired at the leveLa desmostérolose est une maladie autosomale récessive dans laquelle les individus atteints ont un déficit de l'expression de l'enzyme terminale du processus de biosynthèse du cholestérol, connue sous le nom de 3β-hydroxyΔ ² 4cholesterol réductase (DHCR24). Cette enzyme est chargée de convertir le desmostérol en cholestérol. Cette maladie est caractérisée par plusieurs anomalies congénitales, ainsi que par des taux élevés de desmostérol dans le sang accompagnés d'hypocholestérolemie.L'objectif de cette étude a été d'examiner les anomalies provoquées par la desmostérolose au niveau moléculaire ainsi que son impact sur la stéroïdogenèse en utilisant une approche in vitro. Nous avons, pour cela, utilisé la technique d'interférence par des ARN pour diminuer l'expression de l'enzyme DHCR24 reproduisant ainsi les conditions de la desmostérolose dans notre modèle cellulaire.Le cholestérol participe à de nombreux processus de signalisation cellulaire et joue un rôle important dans la stabilité des membranes constituant les cellules. Au cours de notre étude nous avons constaté que le desmostérol du fait de sa structure n'est pas capable de se substituer au cholestérol pour remplir ces fonctions. En effet, les cellules dépourvues de cholestérol pendant 45 minutes ont systématiquement subi un changement de morphologie et ont par la suite présenté les caractéristiques de cellules en apoptose. Ce phénomène était encore plus prononcé dans les cellules où l'expression de DHCR24 avait été diminuée expérimentalement. Nous avons également examiné si le desmostérol pouvait être reconnu par la protéine dite 'domaine de reconnaissance des stérols' (SSD) qui in vivo stimule la synthèse endogène de cholestérol quand ses niveaux dans la circulation sanguine sont trop bas. Pour cela, nous avons mesuré les taux d'expression des protéines suivantes : 'sterol regula
35
Manojlovic, Zarko, Austin Christofferson, Winnie S. Liang, Jessica Aldrich, Megan Washington, Shukmei Wong, Daniel Rohrer, et al. "Comprehensive molecular profiling of 718 Multiple Myelomas reveals significant differences in mutation frequencies between African and European descent cases." PUBLIC LIBRARY SCIENCE, 2017. http://hdl.handle.net/10150/626468.
Full textAbstract:
Multiple Myeloma (MM) is a plasma cell malignancy with significantly greater incidence and mortality rates among African Americans (AA) compared to Caucasians (CA). The overall goal of this study is to elucidate differences in molecular alterations in MM as a function of self-reported race and genetic ancestry. Our study utilized somatic whole exome, RNA-sequencing, and correlated clinical data from 718 MM patients from the Multiple Myeloma Research Foundation CoMMpass study Interim Analysis 9. Somatic mutational analyses based upon self-reported race corrected for ancestry revealed significant differences in mutation frequency between groups. Of interest, BCL7A, BRWD3, and AUTS2 demonstrate significantly higher mutation frequencies among AA cases. These genes are all involved in translocations in B-cell malignancies. Moreover, we detected a significant difference in mutation frequency of TP53 and IRF4 with frequencies higher among CA cases. Our study provides rationale for interrogating diverse tumor cohorts to best understand tumor genomics across populations.
36
Zhang, Xiaomeng. "Significance and molecular basis of Id-1 in regulation of cancer cell survival and invasion." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39325477.
Full text
37
Zhang, Xiaomeng, and 張效萌. "Significance and molecular basis of Id-1 in regulation of cancer cell survival and invasion." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39325477.
Full text
38
Liesenberg, Franziska [Verfasser]. "Aberrant expression of microRNA in gliomas: Molecular mechanisms, functional consequences and clinical significance / Franziska Liesenberg." Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2012. http://d-nb.info/102394698X/34.
Full text
39
Sideris, Michail. "The significance of molecular biomarkers in the recurrence of rectal tumors after Transanal Endoscopic Microsurgery." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/the-significance-of-molecular-biomarkers-in-the-recurrence-of-rectal-tumors-after-transanal-endoscopic-microsurgery(e16b37d2-b2d4-47fb-9c30-563cd06be58d).html.
Full textAbstract:
Local excision (LE) of rectal cancer has been practiced as a treatment for 30 years on a highly selected group of patients and tumours. A method of local excision which has recently gained wider acceptance in the treatment of low-grade CRC (T1) is transanal endoscopic microsurgery (TEMS). TEMS offers advantages for operative access and oncological clearance compared to those of transanal resection (TAR). A number of studies have shown that TEMS can have almost equal results to radical surgery for early rectal cancer. Radical surgery has the disadvantage of an approximate mortality rate of 5% and a complication rate of around 20%, and it impacts on quality of life due to stomas and of sexual dysfunction. However, TEMS has a higher local recurrence rate, and efforts have been made to classify risk with morphological and histological criteria. Molecular biomarkers in the evaluation of CRC prognosis and treatment stratification have been extensively discussed in the literature. Until now, 3 pathways have been identified to explain the background of CRC molecular pathogenesis. Microsatellite instability (MSI) refers to point mutations in the DNA mismatch repair genes. MSI is currently responsible for 15−20% of CRC cases, and there is enough evidence to support its association with prognosis. Chromosomal instability (CIN) is another pathway of carcinogenesis which affects 85% of CRC cases and has been flagged as a poor prognostic marker. CIN encompasses any structural chromosomal abnormality that results in aneuploidy or polyploidy. The third pathway is related to aberrant hypermethylation of suppressor promoter CpG islands, commonly known as CIMP. v-raf murine sarcoma viral oncogene homolog B (BRAF) encodes a serine-threonine protein kinase that acts as a downstream effector of Kirsten rat sarcoma viral oncogene homolog (KRAS) pathways. Various studies have revealed that v-raf murine sarcoma viral oncogene homolog B V600E (BRAF V600E) mutations appear to be valid prognostic indicators. KRAS is a proto-oncogene that encodes a GTPase, which is involved in facilitating cellular response to extracellular stimuli. KRAS point mutations appear in 40% of CRC cases, and their presence is associated with poor response to anti-epidermal growth factor receptor (anti-EGFR) chemotherapy. However, to date there has been no literature linking biomarkers with stratification of risk for the treatment of rectal cancer following TEMS. Aim: The aim of this dissertation is to assess the significance of these molecular biomarkers in the prediction of local recurrence and prognosis of early rectal cancer following TEMS. Materials and Methods: Initially, we performed a narrative review of the literature to consolidate the evidence available for molecular biomarkers in the evaluation of CRC. We then designed a retrospective pilot study to identify the molecular biomarker status of 41 confirmed CRC cases among 1,446 consecutive referrals for suspected cancer. As part of this study, we retrospectively analysed clinical, biochemical, and histopathological data. Gene profile analysis (KRAS, BRAF) of the specimens was also performed. Following this, we proceeded to analyse data from a series of patients who had undergone TEMS for Stage I rectal cancer at King’s College Hospital (KCH). Demographic, biochemical, histopathological, and follow-up data were prospectively collected. Molecular analysis was prospectively performed in the Advanced Diagnostics Laboratory of KCH to identify the status of BRAF, KRAS, p16 O6-methylguanine-DNA methyltransferase (MGMT), and β-catenin. Finally, we retrospectively collected equivalent data on a 4-year series of 135 confirmed Stage I−IV rectal cancer cases who underwent radical surgery +/- neoadjuvant chemoradiotherapy. Data on the status of the same molecular biomarkers were retrospectively collected. In both cohorts of rectal cancer cases (TEMS/radical surgery +/- additional treatment), the biomarker status was compared with the histopathology and follow-up outcomes, including recurrence and overall cancer-related survival. Results: In our pilot study (41 cases), there was no significant correlation of presenting haemoglobin (Hb) levels with eventual disease staging (p>0.05 for all associations). Patients with right-sided tumours were found to have a lower Hb level than patients with either left-sided or rectal tumours. Hb levels were also significantly lower in patients with the BRAF V600E mutation, although this may be because all 3 patients with the mutation had right-sided tumours. Neither KRAS status nor lymphovascular invasion (LVI) status had a specific correlation with Hb levels. Of 29 specimens of cases who underwent TEMS, there was a statistically significant association between KRAS mutant status and local recurrence (n=6, p=0.037). P16 expression > 5% (mean=10.8%, min=0, max=95) was associated with earlier recurrence within 11.70 months (n=7, p=0.004). Membranous β-catenin expression (n=12, 48%) was also related to KRAS mutant (mt) status (p=0.006) but not to survival (p>0.05). BRAF gene was found to be wild type in all cases tested (n=23). With regard to the specimens of rectal cancer cases who underwent radical excision, 28 cases were Stage I (20.9%), n=30; Stage II (22.4%), n=45; Stage III (33.6%) and n=31 Stage IV (23.1. KRAS mt status was associated with female gender (n=20, p=0.021) and older age (69.62 vs. 62.27, p=0.005). Stage I early cancer subgroup analysis showed that KRAS mt status was associated with distant recurrence of disease (n=4, p=0.045). Conclusions: BRAF V600E mutation seems to be associated with right-sided CRC and iron-deficiency anaemia. This could be used as an adjunct to diagnostic molecular tests for early diagnosis. KRAS, p16, and β-catenin could be used as biomarkers for prediction of local recurrence and stratification of the risk for further surgery in Stage I rectal cancer. Further to this, KRAS may be a predictor of distant recurrence in cases of early stage rectal cancer.
40
Yamamoto, Shinichiro. "Reactive Oxygen Species / Reactive Nitrogen Species-sensitive TRP channels : Molecular Activation Mechanism and Physiological Significance." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124503.
Full text
41
Alajtal, Adel I. "Raman spectroscopic application for the analysis of organic compounds and minerals of astrobiological significance. The detection and discrimination of organic compounds and mineral analogues in pure and mixed samples of astrobiological significance using raman spectroscopy, XRD and scanning electron microscopy." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4425.
Full textAbstract:
Raman spectroscopy has been used to characterise both organic and geological samples in order to build a database for the future characterization of biomarker molecules that are of astrobiological relevance. Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA ExoMars mission scheduled for 2018. Several geological features found on the surface of Mars by planetary rovers suggest that a possible extinct biosphere could exist based on similar sources of energy as occurred on Earth. For this reason, analytical instrumental protocols for the detection of isolated biomarkers preserved in suitable geological matrices unequivocally and non-destructively have to be evaluated for future unmanned missions. Raman spectroscopy is currently part of the Pasteur instrumentation suite of the ExoMars mission for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified and the biogeological modifications resulting from extremophilic survival activity have been studied.
Here we present the Raman spectral characterization of several examples of organic compounds which have been recorded using 785 nm, 633 nm and 514 nm laser excitation -polycyclic aromatic hydrocarbons (PAHs), organic acids, chlorophyll and carotenoids. Experimental mixtures of ß-carotene in usnic acid, PAHs in usnic acid and PAHs in mineral matrices have also been investigated. Organic compounds and PAHs located under crystalline minerals samples were identified using a 5x objective lens and 785 nm
III
excitation. The pure compounds and compound mixtures were also analysed using X-ray powder diffraction and scanning electron microscopy (SEM). The results of this study indicate that near infrared laser at 785 nm provided the clearest and the most informative spectra due to the reduction of fluorescence emission. Higher energy lasers operating in the visible region have resulted in the emission of significant background fluorescence. Few samples fluoresce even with the use of 785 nm excitation and FT-Raman spectroscopy remains the instrument of choice for the analysis of these samples.
42
Landry, Sebastien. "Gamma-glutamyl carboxylase gene expression in cultured marrow stromal cells : significance for cell therapy of hemophilia B." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80310.
Full textAbstract:
Gamma-glutamyl carboxylase (GGCX) is an enzyme essential for the post-translational modification of glutamic acid residues found within the gamma-carboxyglutamic acid (GLA) domain of vitamin K-dependent blood coagulation factors as well as other proteins principally involved in bone development such as Osteocalcin and Matrix Gla Protein. We propose that Marrow Stromal Cells (MSC) may serve as a useful Factor IX (FIX) delivery vehicle in vivo. As part of the validation of this cellular delivery platform for gene therapy, we determined whether MSCs endogenously express the GGCX gene. We demonstrated that GGCX was present in MSCs and that it was upregulated as MSCs differentiate into osteoblasts. These results will be of use in the rational development of Marrow Stromal Cells as a delivery vehicle of synthetic gamma-carboxylated therapeutic proteins, including FIX for therapy of Hemophilia B. Furthermore, we wanted to improve upon factor IX gamma-glutamyl carboxylation by generating a fusion FIX protein with enhance carboxylation capabilities. We interchanged the propeptide responsible of the efficiency of this post-translational process of factor IX by the one of the most efficiently gamma-carboxylated proteins, prothrombin.
43
Mahmoud, Tamer I. "The significance of heavy chain CDR3 diversity in the antibody response to polysaccharides." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009p/mahmoud.pdf.
Full text
44
Alajtal, Adel Imhemed. "Raman spectroscopic application for the analysis of organic compounds and minerals of astrobiological significance : the detection and discrimination of organic compounds and mineral analogues in pure and mixed samples of astrobiological significance using raman spectroscopy, XRD and scanning electron microscopy." Thesis, University of Bradford, 2010. http://hdl.handle.net/10454/4425.
Full textAbstract:
Raman spectroscopy has been used to characterise both organic and geological samples in order to build a database for the future characterization of biomarker molecules that are of astrobiological relevance. Characteristic geological features and hydrated minerals recently found on the surface of Mars by the NASA planetary rovers Spirit and Opportunity suggest that a possible biosphere could have once existed there. Analytical instrumentation protocols for the unequivocal detection of biomarkers in suitable geological matrices are critical for future unmanned explorations, including the forthcoming ESA ExoMars mission scheduled for 2018. Several geological features found on the surface of Mars by planetary rovers suggest that a possible extinct biosphere could exist based on similar sources of energy as occurred on Earth. For this reason, analytical instrumental protocols for the detection of isolated biomarkers preserved in suitable geological matrices unequivocally and non-destructively have to be evaluated for future unmanned missions. Raman spectroscopy is currently part of the Pasteur instrumentation suite of the ExoMars mission for the remote detection of extant or extinct life signatures in the Martian surface and subsurface. Terrestrial analogues of Martian sites have been identified and the biogeological modifications resulting from extremophilic survival activity have been studied. Here we present the Raman spectral characterization of several examples of organic compounds which have been recorded using 785 nm, 633 nm and 514 nm laser excitation -polycyclic aromatic hydrocarbons (PAHs), organic acids, chlorophyll and carotenoids. Experimental mixtures of ß-carotene in usnic acid, PAHs in usnic acid and PAHs in mineral matrices have also been investigated. Organic compounds and PAHs located under crystalline minerals samples were identified using a 5x objective lens and 785 nm III excitation. The pure compounds and compound mixtures were also analysed using X-ray powder diffraction and scanning electron microscopy (SEM). The results of this study indicate that near infrared laser at 785 nm provided the clearest and the most informative spectra due to the reduction of fluorescence emission. Higher energy lasers operating in the visible region have resulted in the emission of significant background fluorescence. Few samples fluoresce even with the use of 785 nm excitation and FT-Raman spectroscopy remains the instrument of choice for the analysis of these samples.
45
Pan, Qing, and 潘庆. "Functions and physiological significance of the N- and C- terminal regions of the Escherichia coli global transcription factor FNR." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196081.
Full textAbstract:
A facultative anaerobe such as Escherichia coli is able to switch between the aerobic and anaerobic modes of metabolism in response to O2 availability. This adaptation is primarily controlled by a global transcription regulator called FNR (fumarate nitrate reduction). The key property that allows FNR to act as an O2 responsive transcription factor is its capability to dimerize and being activated upon binding of an O2 labile [4Fe-4S]2+ cluster. Previous functional studies have largely focused on the regions of FNR analogous to CRP (cAMP receptor protein), a prototype CRP/FNR family protein which X-ray crystal structure has been resolved. However, E. coli FNR contains extra N- and C-terminal regions that are conserved among various FNR orthologs but are absent in CRP. The functions of these two regions have not been resolved. In this study, their functions and physiological significance to the O2 sensing capacity of FNR were systematically investigated.
A three-alanine (3-Ala) scanning library on amino acid 2-19 and 236-250 of FNR was constructed and selective 3-Ala substitution mutants exhibited variable defects. These defects were found to be due to their impairment of intracellular FNR protein levels which was unique only among FNR mutations in these two regions. Introduction of 3-Ala substitution at the residues 239-244, resulting in LAQ239-241A3 and LAG242-244A3 respectively, caused an especially accelerated degradation and decrease of intracellular FNR proteins. These variants were found to be degraded by the ClpXP protease. Sequence alignment of FNR orthologs revealed a highly conserved “L239XXL242XG244” motif, and my experimental data further revealed that L239 and L242 were important residues and were responsible for the defects of LAQ239-241A3 and LAG242-244A3, respectively. Circular dichroism analysis revealed that introduction of LAQ239-241A3 caused conformational changes with a significant loss of secondary structures in FNR. These studies taken together suggest that the N- and C-terminal regions of FNR play an important role in mediating the intracellular protein level of FNR. My studies also specified the ClpXP signals as the N-terminal RR9-10 and C-terminal VA249-250, and indicated that VA249-250 is a more important site than RR9-10 in targeting FNR to proteolysis.
The second topic of the thesis involves exploration of the regulatory mechanism of an anaerobically activated multidrug efflux pump MdtEF in E. coli. MdtEF is an important multidrug efflux pump that causes antibiotic resistance upon overexpression. Previous studies revealed that expression of MdtEF was significantly upregulated under anaerobic conditions, but its regulatory mechanism was unknown. In the current study, systematic analyses on the unusually long promoter region of the gadE-mdtEF operon which drives the expression of MdtEF were performed. It was found that unlike FNR, mdtEF was not regulated at post-translational level by proteolysis, but at transcriptional level through the promoter region of gadE. My study showed that anaerobic activation of mdtEF was mediated by the anaerobic regulator ArcA and nitrate responsive regulators NarL and NarP. Important promoter regions P3 and P1 were also identified. This study provides essential molecular basis for the upregulation of MdtEF in a host and clinically relevant conditions.published_or_final_version
Biological Sciences
Doctoral
Doctor of Philosophy
46
Malaney, Prerna. "Significance of PTEN Phosphorylation and its Nuclear Function in Lung Cancer." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6539.
Full textAbstract:
Phosphorylation mediated inactivation of PTEN leads to multiple malignancies with increased severity. However, the consequence of such inactivation on downstream functions of PTEN are poorly understood. Therefore, the objective of my thesis is to ascertain the molecular mechanisms by which PTEN phosphorylation drives lung cancer. PTEN phosphorylation at the C-terminal serine/threonine cluster abrogates its tumor suppressor function. Despite the critical role of the PTEN C-tail in regulating its function, the crystal structure of the C-tail remains unknown. Using bioinformatics and structural analysis, I determined that the PTEN C-tail is an intrinsically disordered region and is a hot spot for post-translational modifications (particularly phosphorylation) and protein-protein interactions. Evolutionary analysis of PTEN and its interacting proteins revealed that the PTEN C-tail has only recently evolved to acquire the ability to engage in a myriad of protein-protein interactions, resulting in its versatile functions.
Replacement of the PTEN C-tail serine/threonine residues with alanines generated an artificial mutant, PTEN-4A, which remained “phospho-deficient” and therefore constitutively active. Interestingly, PTEN-4A suppressed cell proliferation and migration to a greater extent than PTEN-WT. PTEN-4A preferentially localized to the nucleus where it suppressed E2F-mediated transcription of cell cycle genes. PTEN physically interacted with the E2F1 protein and at E2F1-binding sites on chromatin, a likely mechanism for its transcriptional function. Further, deletion analysis on various PTEN domains revealed that the C2 domain of PTEN is indispensable for suppression of E2F-related genes. Systematic transcriptional promoter-reporter assays identified disease-associated C2 domain mutations that lose their ability to suppress E2F-mediated transcription, supporting the concept that these mutations are oncogenic in patients. Consistent with my findings, I observed increased level of PTEN phosphorylation and reduced nuclear PTEN levels in lung cancer patient samples.
Further, to determine whether the enhanced growth-suppressive properties of PTEN-4A may be due to differential protein-protein interactions, I performed a comparative proteomic profiling of PTEN-WT and PTEN-4A interactomes using the SILAC methodology. Galectin-1 was identified as a candidate protein that binds preferentially to PTEN-WT and inhibits its tumor suppressive function. Taken together, the various tumor suppressive mechanisms of PTEN-4A may be harnessed therapeutically as adjunctive cancer therapy. Use of small molecule inhibitors that hinder PTEN C-tail phosphorylation is a plausible approach to activate PTEN function to reduce tumor burden.
47
Sun, Kin-wai, and 孫建維. "The significance of proline rich tyrosine kinase 2 (PYK2) in proliferation and invasiveness of hepatocellular carcinoma." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40687375.
Full text
48
Radinsky, Robert. "The significance of the viral-Kirsten-ras oncogene during tumor progression in a BALB/c 3T3 model system." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1058984282.
Full text
49
Manivannan, Sathiya Narayanan. "TRANSCRIPTIONAL CONTROL OF AN ESSENTIAL RIBOZYME AND AN EGFR LIGAND REVEAL SIGNIFICANT EVENTS IN INSECT EVOLUTION." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1437053490.
Full text
50
Dauksaite, Vita. "The Modular Domain Structure of ASF/SF2: Significance for its Function as a Regulator of RNA Splicing." Doctoral thesis, Uppsala University, Department of Medical Biochemistry and Microbiology, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3579.
Full textAbstract:
ASF/SF2 is an essential splicing factor, required for constitutive splicing, and functioning as a regulator of alternative splicing. ASF/SF2 is modular in structure and contains two amino-terminal RNA binding domains (RBD1 and RBD2), and a carboxy-terminal RS domain. The results from my studies show that the different activities of ASF/SF2 as a regulator of alternative 5’ and 3’ splice site selection can be attributed to distinct domains of ASF/SF2.
I show that ASF/SF2-RBD2 is both necessary and sufficient to reproduce the splicing repressor function of ASF/SF2. A SWQDLKD motif was shown to be essential for the splicing repressor activity of ASF/SF2. In conclusion, this study demonstrated that ASF/SF2 encodes for distinct domains responsible for its function as a splicing enhancer (the RS domain) or a splicing repressor (the RBD2) protein. Using a model transcript containing two competing 3’ splice sites it was further demonstrated that the activity of ASF/SF2 as a regulator of alternative 3’ splice site selection was directional: i.e. resulting in RS or RBD1 mediated activation of upstream 3’ splice site selection while simultaneously causing an RBD2 mediated repression of downstream 3’ splice site usage.
In alternative 5’ splice site selection, the RBD2 alone was sufficient to reproduce the activity of the full-length protein as an inducer of proximal 5’ splice site usage, while RBD1 had the opposite effect and induced distal 5’ splice site selection. The conserved SWQDLKD motif and the RNP-1 type RNA recognition motif in ASF/SF2-RBD2 were both essential for this induction. The activity of the ASF/SF2-RBD2 domain as a regulator of alternative 5’ splice site was shown to correlate with the RNA binding capacity of the domain.
Collectively, my results suggest that the RBD2 domain in ASF/SF2 plays the most decisive role in the alternative 5’ and 3’ splice site regulatory activities of ASF/SF2.