Stereoselective Discrimination and Quantification of Arginine and N-Blocked Arginine Enantiomers by Formation and Dissociation of Calcium-Mediated Diastereomeric Trimer Complexes with a Chiral Reference Compound Using Electrospray Ionization-Ion Trap Tandem Mass Spectrometry

• Published in: Journal of the American Society for Mass Spectrometry Vol. 16; no. 6; pp. 825 - 834
• Main Authors: Schug, Kevin A., Lindner, Wolfgang
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.06.2005; Elsevier Science; Springer Nature B.V
• Subjects: Affinity; Amino acids; Arginine - analysis; Arginine - chemistry; Calcium - chemistry; Calcium compounds; Chemistry; Cluster analysis; Derivatives; Electrospraying; Enantiomers; Exact sciences and technology; Ionization; Ions; Mass spectrometry; Molecular Structure; Organic chemistry; Quantitative analysis; Reactivity and mechanisms; Reference Standards; Scientific imaging; Spectrometry, Mass, Electrospray Ionization; Spectroscopy; Stereoisomerism; Stereoselectivity; Structure-Activity Relationship; Trimer; Separation; Calcium Ions; Electrospray; Alkaline earth metal Ions; Stereoselectivity; α-Aminoacid; Ion trap; Arginine; Optical resolution; Enantiomer; Mass spectrometry MS/MS; Enantiomeric excess; Diastereomer; Quantitative analysis
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/j.jasms.2005.02.008

Chiral resolution of arginine (Arg) and Arg derivatives is demonstrated using electrospray ionization-tandem mass spectrometry (ESI-MS). Calcium ion (Ca II)-mediated trimeric clusters are generated, which incorporate the analyte of interest and an enantiomerically pure reference molecule of similar metal ion affinity. Two methods, one based on the measurement of a competitive-dissociation-based branching ratio (R chir) by the kinetic method (KM) and one based on the measurement of a chiral recognition ratio (CR) by a similar method, are compared. Incorporating N-blocked Arg derivatives (Z-Arg and Boc-Arg) as chiral references provides chiral resolution greater than that previously reported for Arg enantiomers. In a reciprocal manner, pure Arg enantiomers can be used as references for discriminating enantiomers of these N-blocked Arg derivatives. Condensed-phase and gas-phase Ca II ion affinity relative to Arg is also addressed qualitatively for other acidic, basic, and neutral amino acids. In some cases, when only one offspring ion is observed (insufficient for KM analysis), the CR method can be applied as an alternative to obtain a measurable stereoselectivity value for the system. The results of these experiments demonstrate the applicability of, and the difference between, the KM and the CR method for improved quantitative analysis of enantiomeric excess for Arg.