Molecular species analysis of phosphatidylglycerols in Escherichia coli by reversed-phase HPLC/ESI-MS

Abstract

A simple and sensitive method for the determination of molecular species of bacterial phosphatidylglycerols (1,2-diacyl-sn-glycero-3-phospho-1′-sn- glycerol, PG) as an intact form is described. The PG fraction isolated from Escherichia coli IAM12119 was subjected to reversed-phase high-performance liquid chromatography (HPLC) in conjunction with ion-trap mass spectrometry with electrospray ionization (ESI-MS). The HPLC analysis was performed with an ODS column (25 cm x 4.6 mm i.d., 5 μm particle size) using methanol/water/aqueous ammonium hydroxide (93:7:0.1, v/v/v) as the mobile phase, which gave a clear resolution of individual molecular species containing saturated, monounsaturated and cyclopropane fatty acids. In addition to a prominent deprotonated [M-H]- molecule, the negative ESI-MS gave weak product ions, [M-RCO]-, [M-H-RCOOH]- and [RCOO]-, by which individual molecular species could be identified. These product ions, derived from a fatty acid at the sn-2 position, showed greater intensities than those from the sn-1 position. © 2005 The Japan Society for Analytical Chemistry.