Structural investigation of cyclic peptidolipids from Bacillus subtilis byhigh-energy tandem mass spectrometry

The natural products belonging to the surfactin family are cycloheptapeptid es bearing a long beta -hydroxy-fatty acyl chain at the N-terminal position . The structure of these compounds, often isolated as complex mixtures, can be elucidated by high-energy tandem mass spectrometry (MS/MS). The protona ted molecules generated by cesium ion bombardment (LSIMS) undergo charge-pr oximate fragmentations leading to the b- and y-type ion series useful for t he sequence determination. The sodium-cationised molecules show a radically different behaviour towards high-energy collisional activation. Besides th e well-known charge-remote dissociation products of the alkyl side chain, c omplete series of d- and w-type fragments allow easy distinction between le ucine and isoleucine. The complementary MS/MS data obtained from the proton ated and cationised molecules prove to be of great interest for the structu ral characterisation of this type of compounds. Copyright (C) 2001 John Wil ey & Sons, Ltd.