A interface formada por materiais biológicos e materiais sintéticos tem grande importância em aplicações biomédicas, tais como o desenvolvimento de biomateriais para implantes médicos, que tem como processo essencial a deposição de proteínas na superfície dos biomateriais, e ainda não é bem compreendido no nível molecular. Algumas proteínas sofrem mudanças conformacionais após a adsorção na interface sólido-líquido, afetando suas funções ou propriedades, e algumas técnicas podem medir mudanças conformacionais em interfaces sólido. É possível estudar a fluorescência intrínseca de proteínas: a posição do máximo na faixa espectral da fluorescência, a eficiência quântica e o tempo de vida de fluorescência são indicadores de mudanças no ambiente local de grupos de moléculas de proteína fluorescente. Por outro lado, Nanopartículas de ouro têm atraído muita atenção pela sua afinidade com materiais biológicos e suas propriedades ópticas. Nesta tese, estudamos a viabilidade de substratos de vidro, quartzo, mica e ITO (óxido de índio e estanho) modificado com quitosana, phtalocyanines (Ni, Fe e Ni) e poli(alilanina hidroclorada) (PAH) na adsorção de BSA em forma dos filmes produzidos pela técnica camada por camada. O sistema foi estudado por UV-Vis e espectroscopia de fluorescência estática e resolvida no tempo. A caracterização morfológica dos filmes foi realizada por microscopia de força atômica e microscopia óptica. Os resultados mostram que os filmes de BSA / HAP cresceram com eficiência quatro vezes maior do que os filmes feitos de quitosana, que o quartzo tem a melhor janela de trabalho de UV-vis e há uma relação entre o pH da BSA e o tempo vida de fluorescência do filme resultante. As nanopartículas de ouro foram produzidas pela redução química e estabilizada por quatro diferentes métodos. O crescimento das nanopartículas foi monitorado por UV-vis spectroscopy. A carga de superfície das nanopartículas e da BSA foi estimado em vários valores de pH por medidas de potencial zeta. Os resultados indicaram que as nanopartículas têm cargas negativas na faixa de pH estudada. Soluções de BSA foram preparadas em diferentes valores de pH, e levadas para interagir com as nanopartículas de ouro. Os dados de supressão de fluorescência da BSA mostraram uma maior afinidade da BSA com nanopartículas estabilizadas com sacarose, com pH próximo do ponto isoelétrico (IP) estimado para BSA. / The interface formed by biological materials and synthetic materials has great importance in biomedical applications such as the development of biomaterials for medical implants, which has as an essential process of protein adsorption on the surface of biomaterials, and is not yet well understood in the molecular level. Some proteins undergo conformational changes after adsorption at solid-liquid interfaces, affecting their functions or properties, and few techniques can measure conformational changes in solid interfaces. It is possible to study the intrinsic fluorescence of proteins: the position of the maximum in the spectral range of fluorescence, the quantum efficiency and lifetime of fluorescence are indicators of change in the local environment of fluorescent groups of protein molecules. On the other hand, gold nanopartículas have attracted much attention for its affinity with biological materials and their optical properties. In this thesis we study the feasibility of glass substrates, quartz, mica and ITO (Indium tin oxide) modified with chitosan, phtalocyanines (Ni, Fe and Ni) and poly (allylamine hydrochloride) (PAH) on the adsorption of BSA in the form of films produced by the layer by layer technique. The system was studied by UV-Vis and static and time-resolved fluorescence spectroscopy. Morphological characterization of the films was performed by atomic force microscopy and optical microscopy. The results indicate that the films of BSA/PAH grew with efficiency four times greater than the films made of chitosan, that the quartz has the best working window for UV-vis and there is a relationship between the pH of the BSA and lifetime of fluorescence of the resulting film. Gold nanoparticles were produced by chemical reduction and stabilized by four different methods. The growth of nanoparticles was monitored by UV-vis spectroscopy. The surface charge of nanoparticles and the BSA was estimated at various pH values by zeta potential measurements. The results indicated that the nanoparticles have negative charges in the pH range studied. BSA solutions were prepared at various pH values, were taken to interact with gold nanoparticles. Fluorescence quenching data of BSA showed a greater affinity of the BSA with nanoparticles stabilized with sucrose, at pH near the isoelectric point (IEP) estimated for BSA.

Graduation date: 1996

Advances in recent nanoscience technologies have generated a new compilation of biocompatible, fluorescent nanoparticles derived from semiconductor quantum dots (QDs). QDs are extremely small in size and possess very large surface areas, which gives them unique physical properties and applications distinct from those of bulk systems. When exposed to biological fluid, these QDs may become coated with proteins and other biomolecules given their dynamic nature. These protein-QD systems may affect or enhance the changes in protein structure and stability, leading to the destruction of biological function. It is believed that these QDs can act as nucleation centers and subsequently promote protein fibril formation. Protein fibrillation is closely associated with many fatal human diseases, including neurodegenerative diseases and a variety of systemic amyloidoses. This topic of protein-QD interaction brings about many key issues and concerns, especially with respect to the potential risks to human health and the environment. Herein, the behavioral effects of dihydrolipoic acid (DHLA)-capped CdSe/ZnS (core/shell) QDs in hen egg-white lysozyme (HEWL) and human serum albumin (HSA) protein systems were systematically analyzed. This study gives rise to a better understanding of the potentially useful application of these protein-QD systems in nanobiotechnology and nanomedicine as a bioimaging tool and/or as a reference for controlled biological self-assembly processes.

Male rat mating is a suite of individual behaviors mediated by the actions of two metabolites of testosterone (T), dihydrotestosterone (DHT) and estradiol (E2), on the brain. Individually, neither metabolite fully maintains or restores mating in castrated males, but both combined are as effective as T. Two hormone-responsive areas of the brain, the medial preoptic area (MPO) and the medial amygdala (MEA), are crucial for mating. These studies ask: by what mechanism(s) does E2 act in the MPO and MEA? We blocked the conversion of T to E2 in the MEA of intact male rats and sexual behavior was not maintained. We then infused antisense oligodeoxynucleotides (ODNs) to estrogen receptor-alpha (ER-á) mRNA bilaterally to the MPO or the MEA of intact male rats to block ER-á expression. ODN infusion of the MPO attenuated mating but infusion of the MEA had no effect. These results suggest that ER-á is the behaviorally relevant estrogen receptor (ER) in the MPO but not in the MEA. ER was originally described in the cytoplasm and nucleus of cells. Recently plasma membrane associated ERs (mER) have been reported. We conjugated E2 to Bovine Serum Albumin (BSA-E2), a large protein that will not penetrate the plasma membrane, thus restricting the action of E2 to mER, and chronically delivered it to the MPO and MEA. BSA-E2 maintained mating if put in the MPO, but not in the MEA, suggesting a surface action of E2 is sufficient in the MPO. The MPO and MEA are reciprocally connected and probably constitute elements of a larger, steroid-responsive neural network that mediates male mating behavior. To begin to describe this purported circuit, we injected Pseudorabies virus (PRV) into the prostate gland and dually labeled PRV-immunoreactive cells for ER or androgen receptors. We found dual labeling in a forebrain diencephalic circuit that includes the MPO, the medial preoptic nucleus, bed nucleus of stria terminalis, the zona incerta, the periaqueductal gray and other areas that presumably mediate both autonomic and motor aspects of male mating. Together, the results of these studies begin to elucidate locations and mechanisms of E2 mediation of male sexual behavior.

In this study, a methodology for separation of chiral molecules, by using enhanced ultrafiltration system was developed. Benzoin was the model chiral molecule studied. In the scope of developing this methodology, some parameters were investigated in the preliminary ultrafiltration experiments in order to set the operation conditions for enhanced ultrafiltration experiments. Due to the slight solubility of benzoin in pure water, 15% (v/v) Polyethylene glycol (PEG 400) and 30 % (v/v) Dimethyl sulfoxide (DMSO) were selected as cosolvents. Because of the high retention capacity of RC-10000 Da membranes for benzoin, a membrane saturation strategy was developed. In polymer enhanced ultrafiltration (PEUF) experiments bovine serum albumin (BSA) was used as ligand. Effects of ligand concentration and pH on total benzoin retention and on enantiomeric excess (ee %) were investigated. Benzoin concentration was almost kept constant at ~10 ppm and ~50 ppm for 15% (v/v) PEG 400 and 30 % (v/v) DMSO cosolvents, respectively. It was observed that the increase either in pH or in BSA concentration yielded an increase in total benzoin retention. In 15% (v/v) PEG 400-water, with BSA concentration of 10000 ppm, at pH 10, total benzoin retention reached to 48.7%. For this cosolvent, at different pH values and at different BSA concentrations, all ee % values were about or less than 10%. When 50000 ppm BSA was dissolved in 30 % (v/v) DMSO-water, total benzoin retention increased to 41.3% at pH 10 and ee % reached 16.7 % at pH 11. In enzyme enhanced ultrafiltration (EEUF) experiments, specific to benzoin, apo form of Benzaldehyde Lyase (BAL, E.C. 4.1.2.38) was used as ligand. These experiments were performed with constant ~ 10 ppm benzoin concentration in only 15% (v/v) PEG 400 &ndash / water solvent. Effect of BAL concentration on total benzoin retention and ee% was investigated. It was found that / for all the studied BAL concentrations in the range of 650- 1936 ppm total benzoin retention and ee % were kept almost constant at ~75% and ~60%, respectively.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 96-101).

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

A novel approach of using near infrared region (NIR) dyes is applied to elucidate the binding interaction between human serum albumin (HSA) and mangiferin (MGF). HSA is a blood carrier protein used for drug delivery, while mangiferin is a natural polyphenol found in mangoes that possesses numerous beneficial health properties. The NIR dyes are used as a probe to investigate MGF binding interaction with HSA via monitoring fluorescence of Trp-214 residue. Molecular modeling is used for docking and semi-empirical analysis. The investigation of the binding interaction between Trp-214 and MGF is significant, for it may offer broader pharmacological insight and applications for the polyphenol. Mangiferin in proposed to bind with a 2:1 stoichiometric ratio with HSA to the Trp-214 residue in subdomain IIA and another possible binding site to be determined in future studies. Spectral changes suggest a stabilized protein conformation upon mangiferin binding with the addition of NIR dye E-06 and MHI-06.

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 4 uppsatser.

Thesis (M.S.) -- Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.