Quantification of the Redox State of Protein Disulphide Bonds.

To elucidate how a functional disulphide bond controls protein activity, it is critical that the redox state of the bond in the population of protein molecules is known. A differential cysteine alkylation and mass spectrometry technique is described that affords precise quantification of protein disulphide bond redox state. The utility of the technique is demonstrated by quantifying the redox state of 31 of the 37 disulphide bonds in human αIIbβ3 integrin.