用直接法处理Patterson法中的多解问题

测定含重原子晶体的结构,通常都利用Patterson法或以其为基础的重原子法、同晶型法、反常散射法等。此类方法往往会出现多解的情况。作者之一在1965年提出了用直接法消除多解问题的方法。多年来国际上在这方面也一直有类似的探讨。这类方法不仅在分析小分子晶体时有其特点,而且其进一步发展将有助于扩大直接法在生物大分子晶体结构分析中应用的领域,为提高生物大分子晶体结构分析的技术水平作出贡献。作者之一在文献7]中已用实例说明了此类方法在中心对称情况下的应用。本文则提供非中心对称情况下的成功例子。虽然本例只处理了含重原子晶体Patterson函数的双解问题,但所用手段同样适用于处理同晶型法和反常散射法的双解。

THE PROBLEM OF AMBIGUITY IN PATTERSON ANALYSIS TREATED BY DIRECT METHOD

In crystal structure determination with presence of heavy atoms, Patterson method and methods based on it, i.e. the heary atom method, the isomorphous replacement method and the anomalous scattering method are conventionally employed. When applying these methods ambiguities in results often arise. It had been suggested by one of the present authors in 1965 that the ambiguities can be eliminated by using the direct method. In recent years, similar investigations are continued abroad. These methods not only present their distinctive feathures in the work of structure analysis of crystals of small molecules, but their further developements will be effec-tive in extension the field of application of direct methods in structure analysis of biological macro-molecular crystals, making contribution on improving the state of art of these studies. The application of the method in the case of centric symmetry have been demonstrated in the published work of one of the present authors. Another successful example on the case of non-centric symmetry is given here. Although only the problem of ambiguity of Patterson method is treated in this example, but the same approach can be applied to that of the isomorphous replacement method and the anomalous scattering method.