title: Gaussian and linear deconvolution of LC-MS/MS chromatograms of the eight aminobutyric acid isomers.
abstract: Isomeric molecules present a challenge for analytical resolution and quantification, even with MS-based detection. The eight aminobutyric acid (ABA) isomers are of interest for their various biological activities, particularly γ-aminobutyric acid (GABA) and the d- and l-isomers of β-aminoisobutyric acid (β-AIBA; BAIBA). This study aimed to investigate LC-MS/MS-based resolution of these ABA isomers as their Marfey's (Mar) reagent derivatives. HPLC was able to separate three Mar-ABA isomers l-β-ABA (l-BABA), and l- and d-α-ABA (AABA) completely, with three isomers (GABA, and d/l-BAIBA) in one chromatographic cluster, and two isomers (α-AIBA (AAIBA) and d-BABA) in a second cluster. Partially separated cluster components were deconvoluted using Gaussian peak fitting except for GABA and d-BAIBA. MS/MS detection of Marfey's derivatized ABA isomers provided six MS/MS fragments, with substantially different intensity profiles between structural isomers. This allowed linear deconvolution of ABA isomer peaks. Combining HPLC separation with linear and Gaussian deconvolution allowed resolution of all eight ABA isomers. Application to human serum found a substantial level of l-AABA (13 μM), an intermediate level of l-BAIBA (0.8 μM), and low but detectable levels (<0.2 μM) of GABA, l-BABA, AAIBA, d-BAIBA, and d-AABA. This approach should be useful for LC-MS/MS deconvolution of other challenging groups of isomeric molecules.
authors: Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA.
authors: Harika
authors: H
authors: Vemula
authors: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA.
authors: Yukiko
authors: Y
authors: Kitase
authors: Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA.
authors: Navid J
authors: NJ
authors: Ayon
authors: Department of Oral and Craniofacial Sciences, School of Dentistry, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA.
authors: Lynda
authors: L
authors: Bonewald
authors: Division of Pharmaceutical Sciences, School of Pharmacy, University of Missouri-Kansas City, 2464 Charlotte Street, Kansas City, MO 64108, USA. Electronic address: gutheilw@umkc.edu.
authors: William G
authors: WG
authors: Gutheil
mesh_terms: D000613:Aminobutyrates / Q000097:blood*; D002853:Chromatography, Liquid / Q000379:methods; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods*
chemical_list: D000613:Aminobutyrates
keywords: Aminobutyric acid isomers; Chromatographic deconvolution; LC-MS/MS; Marfey's derivatization