Cyanogen bromide cleavage of proteins in salt and buffer solutions

Protocols for recombinant polypeptide production should provide high yields and be efficient, user friendly, and time saving. To perform cyanogen bromide (CNBr) cleavage of fusion proteins, the majority of researchers first desalted and vacuum-dried samples and then dissolved them in aqueous formic or trifluoroacetic acid. We propose to exclude the desalting step and run CNBr cleavage directly. We show that the commonly used Tris-HCl, sodium phosphate, NaCl, imidazole, and guanidine-HCl do not interfere with the reaction under acidic conditions. Omitting the desalting step does not decrease the final yields of target products, as demonstrated for fusion proteins of different origin and composition.