نبذة مختصرة : In my thesis two main projects of my PhD is explained the in chapters 2 and 3 following a pertinent introduction for understanding the projects better in Chapter 1. In chapter 2, the effect of charge repulsion on homo repeat hexapeptides will be explained. The peptides investigated are homo repeats of either acidic (Glu,Asp) or a basic (Arg, His and Lys) amino acid and labeled at two ends for measuring their end-to-end distance and flexibility by methods explained in great detail in chapters 1 and 2. As a function of pH, negative or positive charges appear on the peptide side chains. The repulsion occurs mainly between the N-terminus and the side chains in basic peptides. Astonishingly, no effective negative charge repulsion among the acidic side chains or the C-terminus with the side chains was observed. This can be explained by the difference in binding affinities of water towards carboxylates versus positively charged groups, which results in screening of the negative charges. Charge repulsion between negative charges was recovered when I changed the solvent from water to a 92.5% methanol/water. In the second project –that was explained in Chapter 3− an in vivo host‒dye displacement was carried out: In this project V79 and CHO cells were loaded with a host−dye complex called p-sulfonatocalix[4]arene (CX4) / lucigenin (LCG). The fluorescence of LCG is quenched inside the CX4. The cationic analytes acetylcholine, choline and protamine were sent into the cells. The dye displaced with analyte and made a fluorescence turn-on signal. The invented method can be used for assaying the analyte in the cells. My results also show that CX4 facilitate the membrane passage of LCG. Therefore, CX4 can be considered as a carrier.
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