The main goal in my project was find out if the rate of zinc crossing the bilayer was either due to the fluidity of vesicles or the level of oxidation of the vesicles.To measure the oxidation a simple procedure called the TBA Test was used to measure each PC tested. The fluidity measurement was a calculation using the temperature the vesicles went from gel to liquid crystalline phase and the experimental temperature.Measuring the rate at which zinc crossed the bilayer was done using spectral changes that occur as zinc binds with APIII, a metal chelator entrapped inside the vesicles. To measure these rates we used k', the rate constant at which zinc is crossing the bilayer at a certain concentration and k, the second order diffusion rate constant which is the slope of k' vs. [Zn].The rates at which zinc was crossing the bilayer for each PC was then compared to the fluidity and oxidation levels for each PC. There was no direct correlation between the rates and fluidity but there was a good linear correlation between the rates and oxidation.So it seemed as if oxidation was the main reason zinc was crossing the bilayer so we wanted to see if our measurements could be obtained by biological cells. The comparison showed that rates obtained by biological cells can only be matched by the vesicle models when there oxidation levels are found to be high.In conclusion we believe that the reason zinc is crossing the bilayer is due to oxidation that occurs to the vesicle and as oxidation increases so do the rates at which zinc crosses the bilayer. / Department of Chemistry

Egg phosphatidylcholine was oxidized by atmospheric oxygen under UV light for 16 hours, and the oxidized products formed were fractionated with high-pressure liquid chromatography in reverse phase. Three fractions that appeared at retention times of 19 minutes, 21 minutes and 24 minutes respectively (fraction 19, fraction 21 and fraction 24) were isolated and stabilized by reduction with triphenylphosphine. Zinc diffusion across 1-palmitoyl-2 oleoyl-sn-glycero-3-phosphocholine (POPC) liposome bilayers mixed with the isolated oxidized fractions was measured. The rate constant for zinc diffusion through the POPC liposome was highest in fraction 19 followed by fraction 21 and fraction 24.NMR data suggests that all oxidized fractions were derived from the major egg polyunsaturated PC, 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine. The primary oxidized product, fraction 24 contains a mixture of isomers in which the linoleoyl group has formed the 9-hydroxy-10,12-trans-cis diene and trans-trans diene or the 13-hydroxy12,10-trans-cis diene and trans-trans diene. The primary oxidized products on further oxidation, result in secondary oxidized products, contained in fraction 21 and fraction 19.Experimental data indicates that the major components of fraction 21 are the 9-hydroxy12,13-epoxy-l0-trans-monoene (and 13-hydroxy-9,10-epoxy-11-trans-monoene) and the major components of fraction 19 are the 9,12,13-trihydroxy-l0-trans-monoene (and 9,10,13-trihydroxy-1 l-trans-monoene). / Department of Chemistry

An ionic gradient source and a complimentary transport system regulates the flow of ions across a cell membrane. The major objective of the research focused on analyzing kinetic data to better understand the zinc transport mechanism. This study examined passive diffusion as a possible mode for zinc transport by using a liposome model system. There is a connection between bilayer fluidity (packing order of fatty acids) and rates of diffusion and this was evaluated by choosing lipids that vary with chain length and the degree of saturation or unsaturation. Zinc diffusion kinetics were monitored by observing spectral differences in the visible region of the spectrum in order to determine optimal wavelengths for the calculation of rate constants. The final objective was to calculate a permeability coefficient for each type of liposome and to make comparisons to the permeability of zinc into hepatocytes which has a permeability coefficient of about 1 X 10-7 cm/s. All liposomes used were phosphatidylcholine based. The values of the permeability coefficients for the liposomes used in this project were comparable to permeability in hepatocytes which suggest the potential importance of passive diffusion as a means for transporting biological zinc. / Department of Chemistry

A method was developed which allowed for more consistent liposome quality, reducing the standard error of initial rates for Zn2+ diffusion by 30%. Introducing low concentration of platelet-activating-factor (PAF), 1-palmitoyl-L-lyso-3-phosphocholine (Lyso-PC), or 1-oleoyl-2-acetyl-sn-glycero-3-phosphocholine (Acyl-PAF) to 1palmitoyl.-2-oleoyl-sn-glycero-3-phosphocholine (POPC) liposomes did not have any noticeable impact on zinc diffusion. Since diffusion is dependent on membrane composition and properties, it can be concluded that PAF, Lyso-PC, and Acyl-PAF did not alter POPC liposome properties significantly. Zn2+ and Cd2+ kinetic experiments showed binding to the liposome surface prior to diffusion and a mutual diffusing species, the monohydroxo complex. Although Mn 2+ did not diffuse to any measurable extent, binding to the liposome surface was also observed. Cue+ and Pb 2+ on the other hand follow a more complex diffusion mechanism, which requires further investigation. / Department of Chemistry

No description available.

Experiments were carried out to examine the value of CCS (copper chaperone for CuZn superoxide dismutase) as a novel biomarker of zinc-induced mild copper deficiency and to evaluate the changes in expression of zinc transporters in response to graded levels of moderately high dietary zinc. Weanling male Wistar rats were fed graded levels of zinc (30, 60, 120 and 240 mg zinc/kg diet) for 5 weeks. Results showed a dose-dependent decrease in copper content and an increase in CCS expression in tissues of rats fed the Zn-60 and Zn-120 diets. Surprisingly, rats fed the Zn-240 diet showed better copper status than rats fed the Zn-120 diet. Expression of zinc transporters was significantly upregulated in the small intestine of Zn-240 rats. Collectively, these data show that CCS is responsive to zinc-induced mild copper deficiency, and can serve as a sensitive biomarker of mild copper deficiency. The increased expression of intestinal zinc transporters expression may account for the better copper status of Zn-240 rats.