posted by Peter Parker .
A nonapeptide was determined to have the following amino acid composition: (Arg)2, (Gly)2, (Phe)2, His, Leu, Met.
1-fluoro-2,4-dinitrobenzene (FDNB) reacts with free amino (but not amido or guanidino) groups in proteins to produce dinitrophenyl (DNP) derivatives of amino acids.
The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then completely hydrolyzed; 2,4-dinitrophenylhistidine was identified by HPLC. What does this tell you about the peptide sequence?
When the native peptide was exposed to cyanogen bromide (CNBr), an octapeptide and free glycine were recovered. What does this tell you about the peptide sequence?
Incubation of the native peptide with trypsin gave a pentapeptide, a tripeptide, and free Arg.The peptides were separated and treated with FDNB. 2,4-Dinitrophenyl-histidine was recovered from the pentapeptide, and 2,4-dinitrophenylphenylalanine was recovered from the tripeptide.What does this tell you about the peptide sequence?
Digestion with the enzyme pepsin produced a dipeptide, a tripeptide, and a tetrapeptide. The tetrapeptide was composed of (Arg) 2, Phe, and Gly. What does this tell you about the peptide sequence?
What is the sequence of the nonapeptide?