Question

consider the small peptide Y-R-P-N

a) draw the entire peptide, with charges you would expect on it at pH 7.4.

b) tabulate the charge on the molecule at every pH between 1 and 13

c) calculate the pI for the peptide

d) what is the overall charge on the peptide at ph 1? ph 7.4? ph 13?

e) do you expect this peptide to absorb at 280 nm? why or why not?

f) Mark all the chiral centers in the molecule. how many are there?

Answer 1

The charges on it at pH 7.4 is +1.

Table of charges

pI of the peptide is around  8.88

The overall charge on the peptide at ph 1 is +2, at  ph 7.4 is 0.8 and at ph 13 is -2

Since the peptide contains Tyrosine amino acid that can absorb at 280nm. So this peptide can be measured at 280nm.