Synthesis and single channel conductances of cyclopentane-dicarboxamide linked gramicidin A dimers.

摘要

The main objective of this project was to covalently link two gramicidin A (gA) molecules via trans-1,2-cyclopentane dicarboxylic acid and study the effects of this linker on the functional properties of the ion channel. The results from earlier work showed that proton transfer properties of native gramicidin channels are changed after covalently linking two gA molecules with a dioxolane dicarboxylic acid and its derivatives. To further investigate the biophysical properties of proton transfer, we decided to use a cyclopentane dicarboxylic acid as a novel linker.; The first part of my project was to separate the two enantiomers of trans-1,2-d,l-cyclopentane dicarboxylic acid that is commercially available as a racemic mixture. The acid was treated with brucine, a naturally occurring chiral alkaloid, to convert the diacid to its salt form. The acid salt exists in diastereomeric forms, which were separated by fractional recrystallization. Resolution of these diastereomers was based on their differential solubilities in water. Separated diastereomeric salts were then hydrolyzed to recover the corresponding diacid. Resolution was monitored by measuring the optical rotations of the diastereomeric salts with a polarimeter.; The second part was to work out the synthesis on an organic compound and characterize the product, to check the synthetic route. Later, the procedure was extended to synthesize the gA dimer using racemic trans-1,2-cyclopentane dicarboxylic acid as the linker, optimize the synthetic route, and to characterize the purified synthetic dimer using various techniques. Then the conductance of the synthetic dimer was measured using the bilayer patch-clamp technique.; The third part involved using the optically active diacids i.e., S,S and R,R isolated from the first part, as linkers and to synthesize gA dimers. The synthesized dimers were characterized using various techniques and some conductance measurements were carried out on the synthesized dimers. Finally, compared and analyzed the results obtained from all the dimers.