Thesis (doctoral)--Uppsala Universitet. / Includes bibliography.

Thesis (doctoral)--Uppsala Universitet. / Includes bibliography.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1930. / Typescript. Includes bibliographical references.

A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Medicine 2015 / The dissertation aims to discuss the disulphide and thiol chemistry for use in drug delivery. In particular it focuses on the use of the modified native ovalbumin polymer as a vehicle for the thiol containing captopril. The binding capabilities of thiols expand the area in which peptides and proteins can be used as potential therapeutic drug carriers. It is important that drug delivery systems enhance drug storage stability and in vivo particle stability while delivering the drug efficiently. As part of the developing novel drug delivery systems, thiol-based chemical reactions are distinctive role players in stabilizing disulphide bioconjugated nanostructures for use as efficient drug carrier vehicles in vivo. A review of the current approaches for designing, optimizing and functionalizing nanostructures and conjugates by thiol chemistry modifications was explored. Captopril (Cp) is an Angiotensin-Converting Enzyme (ACE) inhibitor, which acts as an anti-hypertensive, structurally contains a free reactive thiol that binds variably via the thiol/disulphide reaction. A single dose of captopril can regulate hypertension for up to eight hours and the duration of the antihypertensive action of a single dose of 35-75 mg would be taken at 8 hour intervals for 24 hours. Hence the necessities in developing a sustained controlled release ovalbumin carrier system to maintain relatively constant blood pressure levels for 24 hours. The research focused on the construction, characterization and optimization of the thiol conjugated complex for sustained oral drug delivery. The thiol/disulphide-functionalized captopril-ovalbumin conjugate complex was assessed in terms of the structural characteristics and the thiol-disulphide covalent substitution reaction. For analysis of the conjugation complex, the Fourier Transmission IR-spectroscopy (FTIR), H+ NMR and Differential Scanning Calorimetry (DSC) was performed and used to confirm conjugation. Preliminary studies focused on a comparative study of sodium alginate, polyvinyl alcohol and hydroxypropylmethylcellulose hydrogel formulations for the release testing and drug entrapment of the ovalbumin-captopril conjugate complex. Utilizing this data, a series of process variables were used to achieve an optimized formulation through a Box- Behnken statistical design. Furthermore the drug release profiles of the optimised formulation were then analyzed in vitro and in vivo. The captopril released from the formulation was high with a cumulative release of 82%. In vivo analysis was the final testing to verify the validity of the ovalbumin-captopril conjugate complex encapsulated in sodium alginate and utilized a pig model. Ultra Performance Liquid Chromatography (UPLC) blood analysis revealed increased blood levels of captopril (Cmax Cp=33.2ng/mL) in relation to conventional dosage forms validating prolonged (24 hour) site-specific release and increased bioavailability. In conclusion, our validated method was successfully applied to the pharmacokinetic studies of captopril in the blood plasma samples.

This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

Thesis (Ph.D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed on July 14, 2010). Includes bibliographical references (p. 122-142).

Cumulative clinical and experimental evidence indicates that volatile sulphur compounds (VSC) the principal components of oral malodour, may play an important role in the pathogenesis of periodontal disease. As their (H₂S and CH₃SH) concentrations in gingival sulci increase with the severity of periodontal involvement, the objective of this investigation is to ascertain if they exert an effect on the permeability of oral mucosa. Permeability determinations were performed on excised porcine sublingual mucosal specimens which consisted of non-keratinized epithelium, basal membrane and connective tissue layers mounted in a two compartment perfusion apparatus. Using radioactive and fluorescent-labelled penetrants, it was found that exposure of the epithelial surface to an atmosphere containing physiological concentrations of both thiols (15 ng H₂S or CH₃SH / ml of 95% air - 5% C0₂) increased the permeability of the mucosa to (³⁵S)-S0₄⁻², (³H)-prostaglandin E₂ (PGE₂) and fluorescein isothiocyanate labelled E. coli lipopolysaccharide (F-LPS). A three hour exposure of the mucosa to H₂S and CH₃SH resulted in a 75% and 103% increase respectively in permeability to (³⁵S)-labelled sulphate ion. Similarly, the mercaptan induced up to a 70% increase in permeability of the mucosa to (³H)-prostaglandin E₂. The magnitude of changes in the permeability were found to depend on duration of exposure to the thiols and to their concentration. Studies using (³⁵S)-H₂S suggest that the observed changes in the tissue permeability are related to the reaction of the thiols with tissue components. In addition, the (³⁵S)-H₂S is capable of perfusing through all three layers of the mucosa at 12.3 ng / cm². In contrast to H₂S , the CH₃SH effect was irreversible in control air / C0₂ environment. This infers that CH₃SH is potentially a more deleterious agent to the tissue barrier. However, its effect can also be reversed by treatment of tissues with 0.22% ZnCl₂ either prior to or after exposure to mercaptan. This suggests that Zn⁺² ion may be useful in preventing the potentially harmful effects of VSC. Fluorescent studies with F-LPS indicate that thiols can also potentiate the penetration of endotoxin. Whereas the fluorescence of the F-LPS in control systems was confined to the superficial epithelial layer in contact with the endotoxin, the CH₃SH- exposed mucosa exhibited fluorescence throughout the epithelial and connective tissue layers. Fluorescent staining of the mucosal specimens with fluorescein diacetate followed by counter staining with ethidium bromide provides evidence of membrane impairment to some cells by CH₃SH. Collectively these observations provide strong experimental evidence that the VSC, products of putrefaction produced in the gingival sulcus by oral microflora, may adversely affect the integrity of the crevicular barrier to deleterious agents and thus contribute to the etiology of periodontal disease. / Dentistry, Faculty of / Graduate

Made available in DSpace on 2016-08-17T17:39:01Z (GMT). No. of bitstreams: 1 DISSERTACAO_ELYJANY MORAIS LIMA SENA.pdf: 1561186 bytes, checksum: 888156a1b9f61af2c114710a272cf739 (MD5) Previous issue date: 2014-10-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Protein disulfide isomerase (PDI) plays an important role in platelet aggregation involving thiol containing surface proteins in both dependent pathways and independent of ADP. Recently it has been shown that one dodecapeptide (CXXC) containing the catalytic motif PDI was able to decrease the reductase activity of PDI opening the perspective of using the same as antithrombotic therapeutic agent. This study aimed to investigate the effects of peptides PDI - like on platelet aggregation in vitro and molecular mechanism of action of the same. For in silico analysis using a molecular docking program, it was observed that the CXXC peptide as well as its control peptide, scrambled (SCR) and AXXA were all capable of binding to the substrate site of the lligação PDI. Posteriorly, Western blot, it was demonstrated that the peptide CXXC (25  M) induced a slight but significant reduction of free thiols marking PDI suggesting physical association between the peptide and the protein. The same was not observed in samples incubated with Scr and AXXA peptides at the same concentration. In platelet aggregation assays, the platelet-rich plasma (PRP) was pre-incubated with the CXXC, Scr and AXXA peptides using ADP (5  M) as aggregating agent. CXXC found that the peptide reduced the maximum aggregation by 14%, 27% and 30% at concentrations of 3, 10 and 30μM, respectively. The Scr AXXA peptide and the peptide had no effect on platelet aggregation induced by ADP in the same concentrations. Thus, all the data presented here suggest that the CXXC peptide is associated with PDI surface and partially inhibits platelet aggregation via mechanisms mediated by thiol-disulfide exchange. / A Proteína dissulfeto isomerase (PDI) desempenha um importante papel na agregação de plaquetas, envolvendo proteínas tiólicas de superfície tanto em vias dependentes, quanto independentes de ADP. Recentemente foi demostrado que um dodecapeptídeo (CxxC), contendo o motivo catalítico da PDI, era capaz de diminuir a atividade redutase da PDI, abrindo a perspectiva do uso do mesmo como agente terapêutico antitrombótico. Assim, este trabalho teve como objetivo investigar os efeitos de peptídeos PDI símile sobre a agregação plaquetária in vitro e o mecanismo molecular de ação dos mesmos. Por análises in silico utilizando um programa de ancoragem molecular, observou-se que o peptídeo CxxC, bem como os seus peptídeos controle, scrambled (Scr) e AxxA, foram todos capazes de se ligar ao sítio de lligação do substrato na PDI. Posteriomente, por western blot ,demonstrou-se que o peptídeo CxxC (25 M) promoveu uma discreta, mas importante, redução da marcação de tióis livres da PDI sugerindo associação física entre o peptídeo e a proteína. O mesmo não foi observado nas amostras incubadas com os peptídeos Scr e AxxA, na mesma concentração. Nos ensaios de agregação plaquetária, o plasma rico em plaquetas (PRP) foi pré-incubado com os peptídeos CxxC, Scr e AxxA utilizando ADP (5M) como agente agregante. Encontramos que o peptídeo CxxC reduziu a agregação máxima em 14%, 27% e 30% nas concentrações de 3, 10 e 30μM, respectivamente. O peptídeo Scr e o peptídeo AxxA, não afetaram a agregação plaquetária induzida por ADP nas mesmas concentrações. Sendo assim, o conjunto dos dados aqui apresentados sugerem que o peptídeo CxxC associa-se à PDI de superfície e inibe parcialmente a agregação plaquetária via mecanismos mediados por trocas tiol-dissulfeto.

Made available in DSpace on 2015-07-22T20:49:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-29. Added 1 bitstream(s) on 2015-08-11T03:26:18Z : No. of bitstreams: 1 Publico-13280.pdf: 1828173 bytes, checksum: df8fb9928c37e920c5f9a2281ba9c092 (MD5) / O presente trabalho trata do estudo conformacional de S-nitrosotióis com potencial atividade biológica, 2–acetamido-3-metil-3-nitrosossulfanil-N-arilbutanamidas, e de seus tióis precursores, 2–acetamido-3-mercapto-3-metil-N-arilbutanamidas. As conformações de menor energia dos S-nitrosotióis e tióis em estudo são estabilizadas por ligações de hidrogênio intramoleculares que promovem uma maior estabilidade dos confôrmeros. A análise geométrica do grupo R-SNO mostra que esses compostos preferem a conformação trans. O cálculo das interações orbitalares pelo método NBO (Natural Bond Orbital) para as 2–acetamido-3-mercapto-3-metil-N-arilbutanamidas mostrou que as mesmas são estabilizadas pelas seguintes interações: no (N2) →  (C3-O4) e no(N10) → (C11-O12). Os resultados de NBO para os S-nitrosotíois mostraram que a interação hiperconjugativa é bastante efetiva nas conformações estáveis desses compostos, enfraquecendo a ligação que resulta no aumento do comprimento da ligação S-N em S-Nitrosotióis. A forte delocalização , induz caráter parcial a ligação S-N. A fraca ligação S-N indica uma forte delocalização do par de elétrons do O(NO) devido a interação, que é responsável pelo alongamento da ligação S-N, aumentando e a potencial capacidade do óxido nítrico ser liberado. / We carried out a conformational study on the S-nitrosothiols (R-SNO), 2-acetamido-3-methyl-3-(nitrososulfanyl)-N-arylbutanamides and their thiol precursors 2-acetamido-3-mercapto-3-methyl-N-arylbutanamides. The lowest energy conformation for both compounds is stabilized by intramolecular hydrogen bonds. Trans conformation was determined as the predominant conformation after geometrical analysis of R-SNO. Orbital interactions for 2-acetamido-3-mercapto-3-methyl-N-arylbutanamides were calculated using Natural Bond Orbital (NBO) methodology. Calculations indicated that orbital interactions for these compounds are stabilized by the following interactions: no (N2) →  (C3-O4) and no(N10) → (C11-O12). NBO results showed that the hyperconjugative interaction is very effective, weakening the σ bond and resulting in increasing length of the S-N bond in R-SNO. The strong delocalization induces partial character to the S-N bond. The bond S-N indicates a strong delocalization of the electron pair of O(NO) due to interaction. This interaction is responsible for the elongation of the S-N bond which increases the ability of the compound to release nitric oxide (NO). Based on the enhanced capacity to release NO by these compounds, our findings suggest that both compounds may display biological activity. / TEDE / BV UNIFESP: Teses e dissertações