Administration of reseaches on principles of protein architecture

点击翻译按钮获取中文摘要

Proteins, the molecule which play crucially important biological functions, possess its own pattern of conformational fluctuations depending on the three dimensional structure. The fluctuations are suppressed with decreasing temperature, and show a glass transition-like phenomenon at about 200 K.Below 200 K, the protein function is usually lost. Such observations indicate that the fluctuations acquired above the glass transition temperature is crucial for the biological functions. In principle, the glass transition phenomenon can be detected to the atomic detail by a cryo X-ray crystallographic study, as well as various spectroscopic techniques.This work was done by the cooperation between two groups, Go and Kidera in Kyoto University and Parak in Technical University Muenchen. Muenchen group did cryo X-ray measurements at various cryo-temperatures for myoglobin crystals. Kyoto group did analyses of diffraction data provided by Parak using an elaborated refinement method called the nor … More mal mode refinement. We have had close communication including each of two times visits from Kyoto to Muenchen and from Muenchen to Kyoto. Last December when Parak visited Japan, he presented a lecture on this topics in the 5-th workshop of "Principles of protein architectures".The results of the cooperative work is summarized as follows. The internal fluctuations,<R^<**>2>int, derived from the normal mode refinement of X-ray diffraction from myoglobin crystals was found to have temperature dependence of<R^<**>2>int = AT + Bwhere T is absolute temperature, and A an B are constants. The value of A has a good agreement with the value predicted by a normal mode analysis. This means that the conformational substates available below the glass transition temperature is the same as those above the transition temperature. This is why we do not observe abrupt increase in <R^<**>2>int at the glass transition temperature. Therefore, the value B represents the static disorder. This is the view of X-ray diffraction detecting the coherent scattering, which is totally different from the other spectroscopic techniques detecting the incoherent scattering, likeMossbauer absorption spectroscopy. Less