Date of Award
Bachelor of Science
Peptides with secondary characteristics such as α-helices are among the most important structures in nature. Previous studies from Baldwin and coworkers have shown that short alanine-based peptides with specific salt spacing adopt helical conformations. In the study of helix formation, we have synthesized our versions of alanine- and glutamine-based peptides with (i, i + 4) and (i, i + 5) salt spacing. The design of the salt bridge is most suitable when it contains (i, i + 4) salt spacing. The rational is that the (i, i + 4) salt spacing yields a value close to 3.6, the number of amino acids it takes to stabilize one turn of an a-helix, than the (i, i + 5) salt spacing. Using molecular modeling. We have shown that peptides with (i, i + 4) salt spacing indeed formed stabilized salt bridge as opposed to no salt bridge for the (i, i + 5) peptide. The two main strategies for synthesis of the peptides utilize Fmoc as N-α main chain protection and Boc as side chain protection. Both groups display chemical orthogonality in acidic and basic conditions. The yields of the isolated di-TFA salts of both peptides were about 40%. MALDI-MS confirmed that both peptides were synthesized with 65% purity. Using reverse phase HPLC, we purified both (i, i + 4) and (i, i + 5) salt spaced peptides. NMR spectra of both peptides were similar. In future studies, we would like to take CD measurements of our peptides to determine their degree of helicity. In addition, we would like to use cyanogen, a known reagent that traps salt bridges in proteins, and other coupling reagents to react with the salt spacing of our synthesized peptides to forn1 amide links.
Choi, Clark K.N., "Design, synthesis, and characterization of short salt and non-salt bridged peptides" (1997). Honors Theses. 2060.