ANALYSIS OF SULPHUR IN GLUTEN PROTEINS BY X-RAY ABSORPTION NEAR EDGE STRUCTURE (XANES) SPECTROSCOPY

摘要

X-ray absorption near edge structure (XANES) spectroscopy using synchrotron radiation is an excellent method for examining crystalline and non-crystalline biological samples in situ. It combines the penetration strength of X-rays and the advantage of being a local probe technique which does not require long range order. XANES allows insight into the electronic and geometric structure of the environment of the absorbing atom, e.g. the valence of the excited atom as well as the electronegativity of neighbouring atoms even if it is only used as a 'fingerprint method'.' Using this type of approach, the XANES spectrum of the sample to be analysed is compared with those of suitable model compounds yielding 'qualitative information'. To describe quantitatively the contributions of different constituents in a mixture to the XANES spectral features, a 'quantitative analysis' can be performed.2'3 A review on X-ray absorption spectroscopy (XAS) and its application in biological, agricultural and environmental research has been published recently.3 In this paper, we will give a concise introduction to the method and will summarise briefly our results on different aspects of the 'system gluten proteins' obtained by XANES spectroscopy at the sulphur K-edge.