Patent Document ID: 20080032322
Application ID: 11824662
Patent Flag: 0

Claim One:
1. A method for incorporating two labeled oxygen atoms into a digested peptide comprising the steps of: (a) forming a solution of peptidase and H 2 16 O water; (b) digesting a protein into peptides with the solution of peptidase and H 2 16 O water; (c) forming a solution of digested peptides, peptidase and H 2 18 O water; and (d) incubating the digested peptides with the solution of peptidase and H 2 18 O water at a pH range that is ±1 pH unit from a pH which provides a maximum value for an initial rate of reaction for carboxyl oxygen exchange, for a period sufficient to incorporate two labeled oxygen atoms into the digested peptides.