Amino Acid Analysis by Means of MALDI TOF Mass Spectrometry or MALDI TOF/TOF Tandem Mass Spectrometry.

Abstract

Here we describe two different AAA protocols based on application of matrix-assisted laser desorption ionization time-of-flight (MALDI TOF) mass spectrometry (MS). First protocol describes a MALDI TOF MS-based method for a routine simultaneous qualitative and quantitative analysis of free amino acids and protein hydrolysates. Linear responses between the amino acid concentration and the peak intensity ratio of corresponding amino acid to internal standard were observed for all amino acids analyzed in the range of concentrations from 20 to 300μM. Limit of quantitation varied from 0.03μM for arginine to 3.7μM for histidine and homocysteine. This method has one inherent limitation: the analysis of isomeric and isobaric amino acids. To solve this problem, a second protocol based on the use of MALDI TOF/TOF MS/MS for qualitative analysis of amino and organic acids was developed. This technique is capable of distinguishing isobaric and isomeric compounds. Both methods do not require amino acid derivatization or chromatographic separation, and the data acquisition time is decreased to several seconds for a single sample.