C. G. de Koster

Structure identification of natural rhamnolipid mixtures by fast atom bombardment tandem mass spectrometry

Two rhamnobiose-lipid preparations have been studied by fast atom bombardment (FAB) tandem mass spectrometry. The principal rhanobiose-lipids contain the β-hydroxydecanoyl-β-hydroxydecanoate Rha-Rha-C10-C10 and the β-hydroxytetradecanoyl-β-hydroxytetradecanoate Rha-Rha-C14-C14. Both preparations contain minor components which are heterogenous in β-hydroxy fatty acid composition. FAB ionization of rhamnobiose-lipids in the presence of Na+ shows the formation of both [M + Na]+, [M + 2Na - H]+, [M + 3Na - 2H]+ and [M - H]− ions. Tandem mass spectrometry of the [M + 2Na - H]+ and [M - H]− ions give information about the sequence of the building blocks. Particularly, heterogeneity in β-hydroxy fatty acid composition is determined for the principal components and all the minor components present in the preparations.

Four isomeric [C, H3, O2]+ ions

The isomeric ions [HC(OH)2]+, carbonyl oxygen-protonated formic acid [H2C(O+)OH], carbon-protonated formic acid, the methylene hydroperoxy cation, [CH2OOH]+, and the methylperoxy cation, [CH3OO]+, have been characterised by their collisional activation mass spectra, [HC(OH)2]+ and [CH2OOH]+ were generated by dissociative ionisation whereas the other two ions were produced by collisionally induced charge reversal of the corresponding anions. The fragmentations of [HC(OH)2]+ to yield [HC+ O] and [H3O]+ proceed via a common rate-determining energy barrier.

Rapid analysis of enzymatic digests of a bacterial protease of the subtilisin type and a “bio-engineered” variant by high-performance liquid chromatography—frit fast atom bombardment mass spectrometry

Amino acid sequencing of a subtilisin-type bacterial protease and a bio-engineered variant was carried out by investigating various enzymatic digests using HPLC-frit fast atom bombardment MS methods. The fast atom bombardment mass spectral data allowed rapid identification of the enzymatically generated peptides and differentiation between both proteins. The feasibility of determining the positions and nature of mutations in the amino acid sequence depends mainly on the size of the peptides containing the modifications.