Thesis. 1978. Ph.D.--Massachusetts Institute of Technology. Dept. of Chemistry. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Includes bibliographical references. / Ph.D.

A tese em papel está incompleta; tem apenas 112 páginas. O exemplar em CD está completo; inclui bibliografia e anexos / Tese de doutoramento. Ciências de Engenharia. Faculdade de Engenharia. Universidade do Porto, Facoltà di Farmacia. Università degli Studi Cagliari. 2007

Tyrosinase is a widespread, highly studied and important enzyme involved in processes ranging from the browning of mushrooms to roles in mammalian cancer. The enzyme suffers from a noticeable lag phase while the enzyme generates all necessary cofactors from available substrates. There have not been significant studies of the effect on lag from moving through a family of substituted substrates. This thesis reports the results of one such study using a family of N-acyltyramines. The selection of N-acyltyramines was ideal because the substrates in this reaction may be related to synthesis of N-acyldopamines, which serve many important physiological functions. It was concluded that the product formed from N-acetyltyramine is 1-acetyl-2,3-dihydro-1H-indole-6,7-dione, a quinone.

Les formes réactives de l'oxygène (FRO) ont été analysées dans différents compartiments cellulaires en utilisant des méthodes spectroscopiques (UV/VIS, fluorescence, infrarouge, résonance paramagnétique électronique). L'identité et les mécanismes catalytiques des enzymes qui produisent les FRO dans les membranes plasmiques (MP) et les mitochondries ont été étudiés, ainsi que le rôle protectif de l'oxydase terminale plastidiale (PTOX) des chloroplastes. Cd2+ s'est révélé être un inhibiteur de la NADPH oxydase des MP. In vivo Cd2+ inhibait la production extracellulaire de O2•- mais stimulait l'accumulation de H2O2. Dans des mitochondries isolées, Cd2+ a augmenté la production de FRO. Antimycin A a entraîné une élévation du H2O2 extracellulaire, confirmant que la mitochondrie est le site principal de production de l'H2O2 extracellulaire induite par Cd2+ in vivo. Une quinone réductase (QR) génératrice de FRO a été isolée des MP. La déprotonation pH-dépendante du quinole a produit des formes intermédiaires instables qui génèrent des FRO par réaction avec O2. Des espèces quinoniques ont été détectées dans la MP et pourraient servir de substrat aux QR in vivo. La protection de la chaine photosynthétique de transfert d'électron par la plastoquinol:O2 oxydoréductase a été étudiée chez des plantes PTOX+ surexprimant PTOX. En raison de leur réponse altérée en conditions de faible et forte intensité lumineuse, il a été proposé que pour fonctionner comme enzyme protectrice, PTOX est couplée à une SOD. Chez les lignées PTOX+, le niveau de SOD chloroplastique n'était pas plus élevé, limitant probablement leur capacité à détoxifier les taux élevés de O2•- généré.

The cyathins are a unique group of diterpenoids produced by the birds nest fungi <i>Cyathus helenae</i>, <i>C. africanus</i>, and <i>C. earlei</i>. Several of the cyathins show strong antibiotic activity. More recently, several fungal metabolites with structures closely related to those of the cyathins have been found to be potent inducers of nerve growth factor (NGF) synthesis. The structural complexity and the exciting biological activity of the cyathane family of diterpenes have prompted our efforts to develop an efficient and general synthetic approach.<p>To date, there have been seven total syntheses and six partial syntheses of cyathins. Most of these syntheses target allocyathin B2, which does not contain the common 6-7 trans ring fusion or the hydroxyl group within the seven member ring. Modifications of these routes to provide targets with these features have not been demonstrated and may be challenging. We have developed a concise asymmetric synthesis of cyathin A3, based on the enantioselective Diels-Alder reaction of quinone (106) and diene (105). Because the transformations of cyathin A3 into other cyathins are well documented, this synthesis provides a general approach to the cyathane diterpene family. In Section 2.2, the enantioselective Diels-Alder reaction of quinone 106 and diene 105 is presented. This reaction is effectively catalyzed by a carefully prepared Mikami catalyst. It was carried out on a preparative scale to give the chiral building block 108. The absolute configuration of the Diels-Alder adduct 108 was determined by NMR and X-ray analysis.<p>In Sections 2.3-5, the enantioselective total synthesis of (-)-cyathin A3 is described. This approach features the successful oxymercuration ring opening, a newly developed in situ configuration inversion, a much improved intramolecular aldol reaction and a radical cyclization. Now envisioned in our laboratory is the development of a new access to cyathin A4, which is surmised to be possible via the intermediate prepared in this synthesis.

The cyathins are a unique group of diterpenoids produced by the birds nest fungi <i>Cyathus helenae</i>, <i>C. africanus</i>, and <i>C. earlei</i>. Several of the cyathins show strong antibiotic activity. More recently, several fungal metabolites with structures closely related to those of the cyathins have been found to be potent inducers of nerve growth factor (NGF) synthesis. The structural complexity and the exciting biological activity of the cyathane family of diterpenes have prompted our efforts to develop an efficient and general synthetic approach.<p>To date, there have been seven total syntheses and six partial syntheses of cyathins. Most of these syntheses target allocyathin B2, which does not contain the common 6-7 trans ring fusion or the hydroxyl group within the seven member ring. Modifications of these routes to provide targets with these features have not been demonstrated and may be challenging. We have developed a concise asymmetric synthesis of cyathin A3, based on the enantioselective Diels-Alder reaction of quinone (106) and diene (105). Because the transformations of cyathin A3 into other cyathins are well documented, this synthesis provides a general approach to the cyathane diterpene family. In Section 2.2, the enantioselective Diels-Alder reaction of quinone 106 and diene 105 is presented. This reaction is effectively catalyzed by a carefully prepared Mikami catalyst. It was carried out on a preparative scale to give the chiral building block 108. The absolute configuration of the Diels-Alder adduct 108 was determined by NMR and X-ray analysis.<p>In Sections 2.3-5, the enantioselective total synthesis of (-)-cyathin A3 is described. This approach features the successful oxymercuration ring opening, a newly developed in situ configuration inversion, a much improved intramolecular aldol reaction and a radical cyclization. Now envisioned in our laboratory is the development of a new access to cyathin A4, which is surmised to be possible via the intermediate prepared in this synthesis.

Thesis (M.S.) in Chemistry--University of Maine, 2001. / Includes vita. Includes bibliographical references (leaves 61-67).

Quinones represent an important class of endogenous compounds such as neurotransmitters and coenzyme Q10, electrophilic xenobiotics and environmental toxicants that have known reactivity based on their ability to redox cycle and generate oxidative stress, as well as to alkylate target proteins. 1,4-Benzoquinone (BQ) is a reactive quinone that we have used to help predict target residue covalent binding by such compounds. Hydroquinone glutathione conjugates (HQ-GSH) cause renal cell necrosis by producing reactive oxygen species (ROS) and by adducting proteins preferentially localized in the S3 segment of the renal proximal tubules. In vitro experimentation using model peptides and proteins have identified cysteine, lysine, arginine, and glutamic acid as amino acids targeted for quinone-thioether adduction. By mimicking a standard protein digestion protocol (100 mM ammonium bicarbonate pH 7.5, or 50 mM Tris-HCl pH 7.5), we demonstrated that cysteine-BQ adducts are unstable. Taken together, these results indicate that BQ-adduct formation on cysteine residues may be a transient interaction, where physiological conditions may play a role in adduct stability. In vivo experimentation following administration of 2-(glutathion-S-yl)HQ (MGHQ, 400 μmol/kg, iv, 2 hr) to Long Evans rats identified the specific site of quinone-thioether protein adduction on a number of proteins. Urinary proteins were isolated, and either trypsin digested en masse and analyzed by multi-dimensional protein identification technology (MuDPIT) or, following SDS-PAGE, single immunopositive bands were excised, trypsin digested and analysed by LC-MSMS. Following site-specific identification of adducts, 3-dimensional protein modeling of adducts on the protein was performed as a way to reveal the potential structural consequence of the modification on 3D structure. The outer stripe of the outer medulla (OSOM) is the target site of protein adduction caused by quinone-thioethers. Using a 2DGE-Western blot approach, in combination with an extensive knowledge of quinol-thioether chemistry, LC-MSMS, and the latest MSMS analysis software, we identified the specific amino acid site of adduction on 17 unique peptides from 34 target proteins within the OSOM. Of the 22 bands analyzed, adducted peptides were identified in 11 of them. Many of the target proteins identified have previously been identified as a target of other electrophiles, producing additional evidence that such protein adduction is selective rather than random. The site-specific identification of covalently adducted proteins is a prerequisite for understanding the biological significance of chemical-induced PTMs and the subsequent toxicological response.

Typescript. / Thesis (Ph. D.)--University of Hawaii, 1970. / Bibliography: leaves [195]-201. / xviii, 201 l illus., graphs, tables

Thesis (Ph. D.)--Duquesne University, 2003. / Title from document title page. Abstract included in electronic submission form. Includes bibliographical references and abstract.