we propose to determine the structure of an oligopeptide D.
a- the action of b-mercaptoethanol on d gives 2 peptides A and B.
b- the mixture of peptides is treated with 6M HCl, it produces: trp, met, 2 cys, glu, phe, arg, NH4+
c- the carboxypeptidase is active on A but not on B>
d- Hydrolysis of A catalyzed by trypsin produces an amino acid and a dipeptide B1.
B1 migrates to the anode during the electrophoresis in buffer pH=6.5.
the action of FDNB on peptide B produces DNP-cys.
e- 2 peptides A1 and A2 are produced after treatment of peptide A by chymotrypsin. they are separated then put in strong basic solution and at the end treated by strong acidic solution. we need 2 times more strong acid to titrate completely identical quantity of the dipeptides. action of sanger reagent on A2 liberates DNP-cys.
peptide B does not contain a hetercyclic nucleus.
Give the structure of the oligopeptide D.
i came up with:
arg, trp, cys, cys ( met phe glu) NH4+
i couldn't determine the order of met phe and glu. so would anyone help me?
ps: sorry for the long message.