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Practice Problem

      A polypeptide was extracted from the plant Biochimica splendens and given to Mary Lou's gang, who then glibbly went about determining its primary structure.

      Upon hydrolysis of the polypeptide with pronase and paper chromatography, it was found to contain ala, cys, glu, lys, pro and Φala.

      When the polypeptide was treated with FDNB and then pronase hydrolysis, two yellow spots appeared: DNP-cys and εDNP-lys.

      The DNP-polypeptide was also treated with other enzymes and chromatographed:
chymotrypsin yielded two yellow spots A and B.
trypsin yielded three yellow spots C, D and E, and another spot F.

      Spots A and B were eluted and treated with trypsin and re-chromatographed:
A Non-yellow spot G, and yellow spot H
B two yellow spots J and K, and non-yellow spot L.

      Spots G, H, J, K and L were then retreated with FDNB, acid hydrolysed and chromatographed yielding variously colored spots after ninhydrin spraying.

source	yellow	green	blue
G	DNP-pro		Φala
H	DNP-cys	εDNP-lys
J	DNP-ala	εDNP-lys
K	DNP2-lys
L	DNP-glu

      (You can now determine the structure of something - maybe. If you can't, go on:)

      Spots C, D, E and F were then eluted and treated with chymotrypsin and then chromatographed:

C two yellow spots M and N
F one yellow spot P
E one yellow spot Q
D one yellow spot R

      Spots M, N, P, Q and R were then eluted, treated with FDNB, acid hydrolysed, chromatographed and sprayed with ninhydrin:

source	yellow	green	blue
M	DNP2-lys
N	DNP-pro		Φala
P	DNP-glu
Q	DNP-cys	εDNP-lys
R	DNP-ala	εDNP-lys