In trying to deduce a primary structure of an peptide sequence...
When does a polypeptide NOT contain a free carboxyl group? Are all peptides linear (or can they have a cyclic C-terminus)?
What happens when treatment of the intact peptide with 2,4-dinitroflourobenzene (followed by complete hydrolysis and chromatography) yields an amino acid derivitive the involves the amino group of the side chain rather than the alpha-amino group?? Does this matter to the structure of the primary sequence?
Thank you.