Detecting isomers using differential derivatization mass spectrometry

Abstract

Methods of evaluating molecular isomers of branched-chain amino acids are featured. The methods can include: derivatizing one or more molecular isomers of branched-chain amino acids in a sample comprising a branched-chain amino acid labeled with one or more heavy atoms as a first standard; adding, to the sample, after derivatization, a nonderivatized or derivatized branched chain amino acid that is labeled with one or more heavy atoms, as a second standard; evaluating the sample using tandem mass spectrometry; and detecting peaks indicative of derivatized and nonderivatized forms of one or more branched-chain amino acids in the sample.

1 . A kit for evaluating isomers of branched-chain amino acids, the kit comprising:
 a first standard of non-derivatized branched-chain amino acid labeled with one or more heavy atoms; and   a second standard of nonderivatized or derivatized branched-chain amino acid labeled with one or more heavy atoms,   wherein the derivatized forms of the first and second standard have different molecular weights as a result of different heavy atom labeling.   
     
     
         2 . The kit of  claim 1 , further comprising computer software useful for detecting branched-chain amino acids. 
     
     
         3 . The kit of  claim 1 , wherein the branched-chain amino acids include one or more of: leucine, isoleucine, and allo-isoleucine.