Patent ID: 8535948

Claim:
A crosslinker compound useful for modifying proteins for mass spectral analysis which compound is of Formula (I): wherein each of X 1 and X 2 is independently a branched or linear spacer moiety comprising a chain of 2-10 atom members selected from the group consisting of carbon, nitrogen, sulfur, and oxygen, wherein each carbon atom is optionally substituted with =0; wherein at least one of X 1 and X 2 is substituted by an “affinity ligand” that is selected from group consisting of biotin, desthiobiotin, a perfluorocarbon alkyl chain, tert-butyl disulfide, and S-acetyl thioacetate; wherein each “reactive group” is independently a leaving group that reacts with an amine, hydroxyl, sulfhydryl, or carboxyl group of a protein to form a covalent bond with the protein; wherein the cross-linker compound of Formula (I) contains a single MS labile bond that is located at the cleavable site, wherein the cleavable site is (a) a moiety of formula (1), wherein R is H or alkyl C 1-6 : (b) a moiety of formula (2), wherein R is H or alkyl C 1-6 : or (c) a moiety of formula (3): wherein the wavy line in each of the (a)-(c) cleavage site moieties indicates linkages to the spacer moieties X 1 and X 2 ; and wherein the crosslinker portions on either side of the MS labile bond have approximately the same molecular weight, such that the m/z (mass/charge number) value for each is within about 1 Dalton of the other.