Characterization of [1-¹³C]-Specifically Labeled Amino Acids Using ESIMS/MS in the Selected Reaction Monitoring Mode

Abstract

ESIMS/MS was employed for the analyses of 1-¹³CO-labeled amino acids. Conventionally, in order to estimate the ¹³C-content, the intensity of molecule-related ion of the sample has been compared against the natural compound. However, this method is incompetent for specifying the position of the ¹³C-labeling, hence is unable to distinguish the specifically 1-¹³C-labeled compound from otherwise-(generally or non-specifically) labeled amino acids. With the intention of distinguishing 1-¹³CO-labeled amino acids from generally labeled and non-labeled molecules we utilized ESIMS/MS in the selected reaction monitoring mode, choosing the protonated molecules as the precursor ion and specifying the product ion generated by a 47 u- (instead of 46 u-) elimination from the precursor ion for the labeled samples. By this new method, characterization of solely 1-¹³CO-labeled amino acids has been successfully conducted, enabling their distinction from otherwise-labeled compounds.