THE EFFECT OF ENZYMATIC REMOVAL OF PROTEINS FROM PLANT LEAF MATERIAL AS STUDIED BY PYROLYSIS MASS-SPECTROMETRY - DETECTION OF ADDITIONAL PROTEIN MARKER FRAGMENT IONS

This analytical pyrolysis study investigates the effects of ethanol ex traction and of enzymatic protein removal from leaf material of two gr ass species, Poa annua and Paa pratensis. After pyrolysis the leaf fra gments were analysed by low-voltage electron impact (El) and by ammoni a chemical ionization (NH3-Cl). Pronase-treated and untreated material were compared using multivariate analysis of the PyMS data. The resul ting discriminant function spectra among others show a kind of 'negati ve image' of the PyMS spectrum of the plant proteins originally presen t in Poa leaves. In addition to known protein marker fragment ions sev eral hithertoo unrecognised ones were apparent as well. The nitrogen c oncentration was determined for several plant fractions. Quantitative comparison of relative intensities of masses found by discriminant ana lysis led to selection of an additional group of protein marker fragme nts (m/z 54, 70, 84, 107, 130, 209, 225 and 243 for El and 70, 72, 75, 84, 86, 89, 125, 131, 136, 146, 165, 201, 226, 229, 244, 262, 281 and 295 for NH3-Cl) which showed a significant correlation (r(2) > 0.5) w ith the total nitrogen content in the Poa leaves. The origin of grass protein marker fragments was discussed in comparison with reference sp ectra of two new plant cell-wall proteins, a synthetic polyamine and o f albumin. Enzymatic digestion, in addition, yielded a better exposure of the plant cell-wall skeleton, and, therefore, also of the biomacro molecule lignin. Using previously obtained wet chemical data response values were calculated for marker fragments comparative to the analyse d content of proteins, polysaccharides and different lignins. (C) 1997 Elsevier Science B.V.