Thesis (Ph. D.)--Lehigh University, 1999. / Includes vita. Includes bibliographical references (leaves 124-130).

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1998. / Added t.p. with thesis statement inserted.

No description available.

No abstract available. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

Thesis (M.S.), Oregon Graduate Institute of Science & Technology, 1995.

DNA interstrand cross-links are a form of genomic damage that cause a block to replication and transcription of DNA in cells and cause lethality if unrepaired. Chemical agents that induce cross-links are particularly effective at inactivating rapidly dividing cells and, because of this, have been used to treat hyperproliferative skin disorders such as psoriasis as well as a variety of cancers. However, evidence for the removal of cross-links from DNA as well as resistance to cross-link-based chemotherapy suggests the existence of a cellular repair mechanism. Characterizing the pathways involved in DNA interstrand cross-link repair has been challenging due to the inherent structure of the damage as it precludes the use of an undamaged, complementary strand of DNA as a template for repair. A number of models of cross-link repair have been proposed based on the identification of hypersensitive repair mutants as well as biochemical evidence that specific repair enzymes are capable of incising cross-linked structures from DNA. Together, these models have suggested the involvement of multiple repair pathways--such as nucleotide exicision repair, translesion synthesis, recombination of double-strand breaks, and base excision repair--operating in sequential steps to correct the damage. Most of the studies from which these models arose are complicated by the fact that cross-linking agents induce multiple forms of damage or they lack in vivo confirmation of how the repair phenomenon occurs in organisms. In this study, I use Escherichia coli as a model organism to examine the involvement of the aforementioned pathways in DNA interstrand cross-link repair in vivo. This organism was useful in early cross-link studies and, with its highly conserved repair processes, maintains the potential for delineating how cross-links are removed in higher organisms. In Chapter I, I introduce background information on different cross-linking agents, the complications of studying cross-link repair, and the candidate repair pathways that have been implicated to date. In Chapter II I demonstrate that there is a limited involvement of the nucleotide excision repair helicase, translesion polymerases, and double-strand break repair enzymes through survival analysis of cells defective in these proteins. For this analysis, I use 8-methoxypsoralen plus UVA as a cross-linking agent and angelicin plus UVA as a monofunctional comparator. The observation that uvrD mutants-- defective in helicase II of nucleotide excision repair--were nearly as resistant to 8-methoxypsoralen-induced damage as wild type cells led me to examine the incision rate of cross-links from endogenous plasmid DNA. Surprisingly, cross-links were not efficiently removed from DNA in uvrD mutants relative to wild type cells. These seemingly contradictory results were rectified when I quantified cross-link formation in cell cultures and revealed that as few as one cross-link per chromosome can inactive wild type cells, a lethal quantity that is lower than what has been previously reported. Taken together, these observations suggest that although cross-links are incised in wild type cells, repair is still not a highly productive event in E. coli. In Chapter III I examine the involvement of the base excision repair pathway in cross-link repair and demonstrate that Nth and Fpg Glycosylases, Xth and Nfo AP-Endonucleases sensitize Escherichia coli to psoralen-induced DNA damage. This is shown by comparative survival analysis in angelicin plus UVA and 8-methoxypsoralen plus UVA treatment whereby nth-, fpg-, and xth-mutants are each more resistant than wild type cells to either treatment. This suggests that when these gene products are present they impact the production or removal of monoadducts. nfo-mutants were different in that the cells were only hyperresistant to 8-methoxypsoralen monoadducts and cross-links, either implying that the Nfo enzyme interacts specifically with psoralen monoadducts rather than angelicin monoadducts or that the enzyme impedes cross-link removal. Finally, in Chapter IV a summary of the results is provided as well as future directions that may be explored following this study.

M.S. / Applied Physics / A new method of measuring the level of 8-methoxypsoralen in blood serum was developed for the reasons of speed, accuracy, and cost. This new method uses laser induced fluorescence of the psoralen to determine the concentration in serum. The fluorescence is analyzed with an optical multichannel analyzer coupled to an intensified photodiode array detector. Research was first attempted on samples with ethanol as the solvent to confirm that the method would work. Sample concentrations of 8-methoxypsoralen in serum are determined by comparing the fluorescence signal obtained from previously known concentrations. Levels down to 200ng per milliliter of serum can be measured with this technique.

No description available.

126f. / Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-03-22T15:11:05Z No. of bitstreams: 1 Tese_Lidércia.pdf: 1854558 bytes, checksum: 7d54dd03b3bb8154f1ce2f0564633c7d (MD5) / Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-04-19T13:36:52Z (GMT) No. of bitstreams: 1 Tese_Lidércia.pdf: 1854558 bytes, checksum: 7d54dd03b3bb8154f1ce2f0564633c7d (MD5) / Made available in DSpace on 2013-04-19T13:36:52Z (GMT). No. of bitstreams: 1 Tese_Lidércia.pdf: 1854558 bytes, checksum: 7d54dd03b3bb8154f1ce2f0564633c7d (MD5) Previous issue date: 2009 / CAPES / Este trabalho foi desenvolvido no âmbito do PRONEX – NQA e descreve o estudo através da técnica da Cromatografia Líquida de Alta Eficiência acoplada a detector de arranjo de diodos - CLAE-DAD nas análises de amostras de sucos de laranja obtidos por processos extrativos diversificados (espremidos a mão, extração em condições industriais com posterior comercialização em longo prazo e obtido através de máquinas tipo fresh-in-squeeze) para a identificação de flavonóides e psoraleno. Os diversos sucos foram submetidos às etapas de extração líquido-líquido e posterior análises por CLAE-DAD. Estes procedimentos permitiram identificar e quantificar algumas flavanonas e psoraleno presentes nos sucos cítricos. Dentre as flavanonas se determinou hesperidina, naringina, naringenina e poncirina. As faixas de concentrações destes compostos variaram de 17,8 - 245 mg 100 g-1 para hesperidina, 0,01 – 0,08 mg 100 g-1 para naringina, 0,05 – 0,170 mg 100 g-1 para naringenina e de 0,06 – 0,36 mg 100 g-1 para poncirina. Quanto ao psoraleno, em algumas amostras dos sucos, as concentrações estavam abaixo do limite de quantificação (< 0,02) e variou de < 0,02 – 0,05 mg 100 g-1. Estes resultados sugerem que o modo de obtenção dos sucos e os critérios de extração dos constituintes podem influenciar tanto nos teores dos flavonóides no suco como nas detecções de suas concentrações através da técnica aplicada. Para exames das informações geradas foram empregadas metodologias estatísticas multivariadas por meio de Análises de Componentes Principais (PCA) e Análise de Agrupamentos Hierárquicos (HCA) executando o estudo exploratório dos dados para avaliar tendências e discriminar amostras dos sucos de laranja quanto a sua origem, tipos de tratamentos de extração e características químicas para os teores de flavonóides e psoraleno. / Salvador