Question: determine the primary sequence of the polypeptide many individual chains...
Determine the primary sequence of the polypeptide, many individual chains it is made up of, and if/where disulfide bonds may exist.
Amino acid analysis revealed the following composition for the decapeptide - Arg, (Cys)2, Gln, Gly, Lys, Met, Pro, Ser, Tyr
Reverse phase HPLC was run on the peptide under both reducing and non-reducing conditions. A single peak was observed under non-reducing conditions, whereas under reducing conditions two pentapeptides were isolated.
Treatment of the decapeptide with FDNB followed by acid hydrolysis resulted in the detection of DNB-Gly (peak 1) and DNB-Cys (peak 2).
Treatment of the pentapeptides with CNBr gave the following results: Peak 1 produced a dipeptide and a tripeptide. Peak 2 resulted in no reaction. Treatment of the intact decapeptide with CNBr gave the following result under non-reducing conditions: A tripeptide and a heptapeptide were produced. Reaction of the heptapeptide with FDNB followed by acid hydrolysis resulted in the production of DNB-Gln being detected (along with DNB-Cys).
Treatment of the heptapeptide with chymotrypsin resulted in no cleavage. Treatment of the heptapeptide with pepsin resulted in a dipeptide and pentapeptide.
Treatment of the heptapeptide with trypsin resulted in the generation of free arginine, a dipeptide, and a tetrapeptide.