[snowy88]

Hi this problem is killing me, I know the C and N terminus from the information provided but actually figuring out the sequence is proving a bit difficult.  

A nonapeptide was determined to have the following amino acid composition: (Lys)2, (Gly) 2, (Phe) 2, His, Leu, Met.  The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycine were recovered.  Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and free Lys.  2,4-Dinitrophenyl-histidine was recovered from the pentapeptide, and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide.  Digestion with the enzyme chymotrypsin produced a dipeptide, a tripeptide, and a tetrapeptide.  The tetrapeptide was composed of (Lys) 2, Phe, and Gly.  

23.   What is the sequence of the peptide?

A)   His–Phe–Lys–Lys–Gly–Leu–Met–Gly–Phe.
B)   His–Leu–Gly–Lys–Lys–Phe–Phe–Met-Gly.
C)   His–Leu–Phe–Gly–Lys–Lys–Phe–Met–Gly.
D)   His–Phe–Leu–Gly–Lys–Lys–Phe–Met–Gly.
E)   Met–Leu–Phe–Lys–Phe–Gly–Gly–Lys–His.

Obviously has to be either B,C or D

[Biopolmonkey]

Where does trypsin cleave? For B, C and D draw what the effects of treating with trypsin would be.

Which, then,  would allow this statement to be true: "2,4-Dinitrophenyl-histidine was recovered from the pentapeptide, and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide".

Do the same for chymotrypsin.