Suppose a researcher isolates a peptide from brain tissue that binds to the same receptor as an opiate drug. This peptide is an opioid enkephalin, a class of endogenous peptides that act within the brain to lower pain sensation. The researcher performs a series of procedures to determine the peptide’s sequence. First, the researcher completely hydrolyzes the peptide by boiling in an 185% w/w HCl solution. Analysis of the hydrolysis products indicates the presence of Gly, Leu, Phe, and Tyr, in a 2:1:1:1 molar ratio. Chromatography of the products after dansylation indicates the presence of the dansyl-amino-acid derivative of tyrosine. No free tyrosine is present. Given the empirical composition and the results from the dansyl chloride reaction, where is Tyr located in the peptide?
interior of the peptide
cannot be determined from these results
N-terminus
C-terminus
Leave a Reply