MASS-SPECTROMETRIC SEQUENCING OF PROTEINS FROM SILVER-STAINED POLYACRYLAMIDE GELS

Proteins from silver-stained gels can be digested enzymatically and th e resulting peptides analyzed and sequenced by mass spectrometry. Stan dard proteins yield the same peptide maps when extracted from Coomassi e- and silver-stained gels, as judged by electrospray and MALDI mass s pectrometry, The low nanogram range can be reached by the protocols de scribed here, and the method is robust. A silver-stained one-dimension al gel of a fraction from yeast proteins was analyzed by nanoelectrosp ray tandem mass spectrometry. In the sequencing, more than 1000 amino acids were covered, resulting in no evidence of chemical modifications due to the silver staining procedure, Silver staining allows a substa ntial shortening of sample preparation time and may, therefore, be pre ferable over Coomassie staining. This work removes a major obstacle to the low-level sequence analysis of proteins separated on polyacrylami de gels.