Structural determination of synthetic monoacetyldiglycerides by tandem mass spectrometry of sodium-adducted molecules

A variety of synthetic monoacetyldiglycerides (MADGs), which show hematopoi etic stem cell stimulating activity, were investigated using high-energy co llision-induced dissociation (CID) tandem mass spectrometry (MS/MS) coupled with fast-atom bombardment (FAB), CID of sodium-adducted molecules, [M + N a](+), generated product ions highly informative on their structure. In par ticular, two type of ions (named E-2,E-3 and J) and the relative intensity ratio (G(2)/G(1)) of two product ions (named G(1) and G(2)) by the loss of free fatty acids (-R-n' COOH) provided definitive information about the pos ition of two long-chain acyl groups on the glycerol backbone. In addition, charge-remote fragmentation (CRF) along the long hydrocarbon chains of two fatty acyl groups determined the position of each double bond. Thus, this d irect and rapid method can be applied to the structural determination of in dividual molecular species in a mixture of MADGs isolated from biological o rigins. Copyright (C) 1999 John Wiley & Sons, Ltd.