Patent Document ID: 8580534
Application ID: 11824662
Patent Flag: 1

Claim One:
1. A method for incorporating two labeled oxygen atoms into a digested peptide comprising the steps of: forming a first solution of a first peptidase and H 2 16 O water; digesting a protein into peptides with the first solution of the first peptidase and H 2 16 O water; and incubating the digested peptides with a second solution of a second peptidase selected from the group consisting of Lys-C and trypsin and H 2 18 O water, the second solution having a pH within 1 pH unit of a pH which provides a maximum initial rate of reaction for carboxyl oxygen exchange for the digested peptides catalyzed by the second peptidase, for a period sufficient to incorporate two labeled oxygen atoms into at least 90% of the digested peptides.