The use of triethylammonium bicarbonate (TEAB) solution in electrospray mass spectrometry proved to be a very efficient way for studying proteins or noncovalent protein complexes under "nondenaturing" conditions. The low charge states observed in the mass spectra improve the separation of ions arising from macromolecular species of close masses. Moreover, the multiply charged ions generated in a TEAB solution are significantly more stable than those formed under more conventional conditions (for example, with ammonium bicarbonate or acetate solution). The analytical interest of TEAB for the analysis of macromolecular species that can easily dissociate in the gas phase, such as hemoglobin or other macromolecular noncovalent complexes, is demonstrated.

The natural products belonging to the surfactin family are cycloheptapeptides bearing a long β‐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 protonated molecules generated by cesium ion bombardment (LSIMS) undergo charge‐proximate fragmentations leading to the b‐ and y‐type ion series useful for the sequence determination. The sodium‐cationised molecules show a radically different behaviour towards high‐energy collisional activation. Besides the well‐known charge‐remote dissociation products of the alkyl side chain, complete series of d‐ and w‐type fragments allow easy distinction between leucine and isoleucine. The complementary MS/MS data obtained from the protonated and cationised molecules prove to be of great interest for the structural characterisation of this type of compounds. Copyright © 2001 John Wiley & Sons, Ltd.

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