The present invention relates to methods of cleaving the N-terminal amino acid from a polypeptide, which may be in free form or conjugated to a carrier or surface, such as a bead. It provides methods to activate the N-terminal amine of a polypeptide to promote formation of a cyclic adduct of the N-terminal amino acid, resulting in cleavage of the N-terminal amino acid from the polypeptide. The method can be used to sequence and/or analyze a polypeptide. For example, the methods can be combined with methods described herein for sequencing and/or analysis that employ barcoding and nucleic acid encoding of molecular recognition events, and/or detectable labels. The invention also provides compounds and kits useful for practicing these methods.

Methods for analyzing, selecting, characterizing or classifying compositions of a co-polymer, e.g., glatiramer acetate are described. The methods entail analysis of pyro-glutamate in the composition, and, in some methods, comparing the amount of pyro-glutamate present in a composition to a reference standard.

Methods for analyzing, selecting, characterizing or classifying compositions of a co-polymer, e.g., glatiramer acetate are described. The methods entail analysis of pyro-glutamate in the composition, and, in some methods, comparing the amount of pyro-glutamate present in a composition to a reference standard.