MICROHETEROGENEITY CHARACTERIZATION OF A PARACELSIN MIXTURE FROM TRICHODERMA-REESEI USING HIGH-ENERGY COLLISION-INDUCED DISSOCIATION TANDEMMASS-SPECTROMETRY

The microheterogeneity of the paracelsin mixture broth of Trichoderma reesei was analysed using mass spectrometric methods, in particular hi gh energy collision-induced dissociation (CID) tandem mass spectrometr y (MS/MS). Based on the liquid secondary ion mass spectrum of the mixt ure, there are three main components, with molecular masses M and (M /- 14), together with two minor components of molecular weight (M +/- 28). The high-energy CID tandem mass spectra of both the protonated an d sodiated molecules yielded abundant and characteristic fragment ions , but of very different types. It was found that a paracelsin peptaibo l in a mixture could be successfully sequenced based on the tandem mas s spectra of its protonated and sodiated molecules or, alternatively, on the tandem mass spectra of its y(7) and b(13) fragment ions. A term inology for indicating these sequential peptide fragments is proposed. To determine the sequence of new analogues, tandem mass spectra of th e y(7), (y(7) +/- 14), b(13), (b(13) +/- 14) and (MH +/- 14) positive ions were also taken. Based on these experiments, four new paracelsin components (PA-F, PA-G, PA-H and PA-I) were sequenced successfully. Th e microheterogeneity of the mixture was found to be more pronounced th an had been assumed previously. In these new analogues, besides positi ons 6 and 9, position 17 is also involved in the exchange. MS/MS studi es on minor fragment ions, such as (b(13) - 28) and (b(8) - 14) show f urther microheterogeneity at positions 3, 5, 10 and 12, which increase the number of possible minor components. (C) 1997 by John Wiley & Son s, Ltd.