The Use Of Amido- And Imido-Functionalized Alpha Hydroxy Acids In The Creation Of Biodegradable Polyesters: An Exploration Of Va

The purpose of this thesis was to synthesize biodegradable polyesters from a wide array of functionalized ¿-hydroxy acids. The initial strategy was to use amido-functionalized ¿-hydroxy acids and 2-bromopropanoyl bromide to form amido-functionalized cyclic diesters. Then, the resulting cyclic diesters would be used in ring opening polymerization to create biodegradable polyesters. However, the spontaneous rapid degradation of the secondary amido-functionalized cyclic diester structure, as seen with 2-benzamido-hydroxyacetic acid, limited ring formation to tertiary amido-functionalized ¿-hydroxy acids. Also, the hydrophilic nature of most ¿-hydroxy acids allowed water into the crystal structure of the ¿-hydroxy acid. Then, when the ¿-hydroxy acid was used in ring forming reactions, the associated water deactivated reactive reagents and limited cyclic diester synthesis. These issues led to the synthesis of hydrophobic and tertiary amido- and imido-functionalized ¿-hydroxy acids, 2-phthalimido-2-hydroxyacetic acid and 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid. The new ¿-hydroxy acids were used in two new polymerization techniques, melt polycondensation and solution polymerization, instead of ring open polymerization. Melt polycondensation and solution polymerization had shown previous success in forming oligomers of amido-functionalized ¿-hydroxy acids. Melt polycondensation was conducted by heating the monomer past its melting temperature under reduced pressure. The uncatalyzed melt polycondensation of 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid created polyesters (¿ 960 g/mol). The scandium(III) trifluoromethanesulfonate enhanced melt polycondensation polymerization created slightly larger oligomers (¿ 1340 g/mol). However, 2-phthalimido-2-hydroxyacetic acid was not compatible with melt polycondensation because thermal degradation occurred. Thus, solution polymerization was conducted via Steglich esterification. Only oligomeric functionalized polyesters were formed (¿ 1060 g/mol). Future work should focus on optimization of the catalyst and the reaction conditions to obtain higher molecular weight polyesters. Also, 2-(1-oxoisoindolin-2-yl) hydroxyacetic acid should be utilized in the cyclic diester synthesis technique.

Hexose-6-phosphate dehydrogenase modulates 11beta-hydroxysteroid dehydrogenase type 1-dependent metabolism of 7-keto- and 7beta-hydroxy-neurosteroids

BACKGROUND: The role of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) in the regulation of energy metabolism and immune system by locally reactivating glucocorticoids has been extensively studied. Experiments determining initial rates of enzyme activity revealed that 11beta-HSD1 can catalyze both the reductase and the dehydrogenase reaction in cell lysates, whereas it predominantly catalyzes the reduction of cortisone to cortisol in intact cells that also express hexose-6-phosphate dehydrogenase (H6PDH), which provides cofactor NADPH. Besides its role in glucocorticoid metabolism, there is evidence that 11beta-HSD1 is involved in the metabolism of 7-keto- and 7-hydroxy-steroids; however the impact of H6PDH on this alternative function of 11beta-HSD1 has not been assessed. METHODOLOGY: We investigated the 11beta-HSD1-dependent metabolism of the neurosteroids 7-keto-, 7alpha-hydroxy- and 7beta-hydroxy-dehydroepiandrosterone (DHEA) and 7-keto- and 7beta-hydroxy-pregnenolone, respectively, in the absence or presence of H6PDH in intact cells. 3D-structural modeling was applied to study the binding of ligands in 11beta-HSD1. PRINCIPAL FINDINGS: We demonstrated that 11beta-HSD1 functions in a reversible way and efficiently catalyzed the interconversion of these 7-keto- and 7-hydroxy-neurosteroids in intact cells. In the presence of H6PDH, 11beta-HSD1 predominantly converted 7-keto-DHEA and 7-ketopregnenolone into their corresponding 7beta-hydroxy metabolites, indicating a role for H6PDH and 11beta-HSD1 in the local generation of 7beta-hydroxy-neurosteroids. 3D-structural modeling offered an explanation for the preferred formation of 7beta-hydroxy-neurosteroids. CONCLUSIONS: Our results from experiments determining the steady state concentrations of glucocorticoids or 7-oxygenated neurosteroids suggested that the equilibrium between cortisone and cortisol and between 7-keto- and 7-hydroxy-neurosteroids is regulated by 11beta-HSD1 and greatly depends on the coexpression with H6PDH. Thus, the impact of H6PDH on 11beta-HSD1 activity has to be considered for understanding both glucocorticoid and neurosteroid action in different tissues.

Sonic log prediction in carbonates

This work is conducted to study the complications associated with the sonic log prediction in carbonate logs and to investigate the possible solutions to accurately predict the sonic logs in Traverse Limestone. Well logs from fifty different wells were analyzed to define the mineralogy of the Traverse Limestone by using conventional 4-mineral and 3-mineral identification approaches. We modified the conventional 3-mineral identification approach (that completely neglects the gamma ray response) to correct the shale effects on the basis of gamma ray log before employing the 3-mineral identification. This modification helped to get the meaningful insight of the data when a plot was made between DGA (dry grain density) and UMA (Photoelectric Volumetric Cross-section) with the characteristic ternary diagram of the quartz, calcite and dolomite. The results were then compared with the 4-mineral identification approach. Contour maps of the average mineral fractions present in the Traverse Limestone were prepared to see the basin wide mineralogy of Traverse Limestone. In the second part, sonic response of Traverse Limestone was predicted in fifty randomly distributed wells. We used the modified time average equation that accounts for the shale effects on the basis of gamma ray log, and used it to predict the sonic behavior from density porosity and average porosity. To account for the secondary porosity of dolomite, we subtracted the dolomitic fraction of clean porosity from the total porosity. The pseudo-sonic logs were then compared with the measured sonic logs on the root mean square (RMS) basis. Addition of dolomite correction in modified time average equation improved the results of sonic prediction from neutron porosity and average porosity. The results demonstrated that sonic logs could be predicted in carbonate rocks with a root mean square error of about 4μsec/ft. We also attempted the use of individual mineral components for sonic log prediction but the ambiguities in mineral fractions and in the sonic properties of the minerals limited the accuracy of the results.

The Electroplating of Cadmium from Sulfate Solutions

It has been proven that cadmium forms a very satisfactory plate on steel, which has to withstand severe corrosion, especially the corrosion of sea water and spray. The metal is now successfully plated electrolytically from cyanide solutions, but wherever work is carried on with cyanide, there is great danger of poisoning to the workers.

Hydrogen Overvoltage of Cadmium Bismuth and Antimony Bismuth Alloys

A method to measure hydrogen overvoltage was devel­oped and checked with metals of known overvoltage. Alloys of bismuth and antimony and of bismuth and cad­mium were prepared and their overvoltages determined.

Separation of Cadmium from Zinc in the Purification Step of the Leaching Cycle

The purpose of this investigation is to determine the effect of the factors listed previously by conducting a series of tests that will indicate the ex­tent to which the purification is influenced by time, temperature, zinc oust size, zinc dust quantity, iron concentration, two stage precipitation, and aeration.

Human TRPV5 and TRPV6: key players in cadmium and zinc toxicity

TRPV5 and TRPV6 are two major calcium transport pathways in the human body maintaining calcium homeostasis. TRPV5 is mainly expressed in the distal convoluted and connecting tubule where it is the major, regulated pathway for calcium reabsorption. TRPV6 serves as an important calcium entry pathway in the duodenum and the placenta. Previously, we showed that human TRPV6 (hTRPV6) transports several heavy metals. In this study we tested whether human TRPV5 (hTRPV5) also transports cadmium and zinc, and whether hTRPV5 together with hTRPV6 are involved in cadmium and zinc toxicity. The hTRPV5 mRNA and protein were expressed in HEK293 cells transiently transfected with pTagRFP-C1-hTRPV5. The overexpression of the hTRPV5 protein at the plasma membrane was revealed by cell surface biotinylation and immunofluorescence techniques. We observed that both cadmium and zinc permeate hTRPV5 in ion imaging experiments using Fura-2 or Newport Green DCF. Our results were further confirmed using whole-cell patch clamp technique. Transient overexpression of hTRPV5 or hTRPV6 sensitized cells to cadmium and zinc. Toxicity curves of cadmium and zinc were also shifted in hTRPV6 expressing HEK293 cells clones. Our results suggest that TRPV5 and TRPV6 are crucial gates controlling cadmium and zinc levels in the human body especially under low calcium dietary conditions, when these channels are maximally upregulated.