ACCOUNTS OF CHEMICAL RESEARCH Accounts of Chemical Research (ISSN 0001-4842) is published monthly by the American Chemical Society at 1155 16th Street, N.W., Washington, DC, 20036. Second-class postage paid at Washington, DC and additional mailing offices. POSTMASTER: Send address changes to Membership & Subscription Services, PO Box 3337, Columbus, OH, 43210. © Copyright, 1982, by the American Chemical Society. Permission of the American Chemical Society is granted for libraries and other users to make reprographic copies for use beyond that permitted by Section 107 or 108 of the U.S. Copyright Law, provided that the copying organization pay the appropriate per-copy fee through the Copyright Clearance Center, Inc., 21 Congress St., Salem, MA 01970. For reprint permission, please write to the Copyright Administrator, Books and Journals Division, at the ACS Washington address. Editorial Information Accounts of Chemical Research publishes concise, critical reviews of research areas currently under active investigation. Most articles are written by scientists active in the area reviewed. Reviews may be concerned in large part with work in the author's own laboratory, providing that relevant contributions by other investigators are mentioned sufficiently to place the author's research in perspective. Also published are occasional articles in which the author offers a critical assessment of a subject that has become somewhat muddled or even controversial, and proposes unifying concepts to clarify it. Articles should be directed concurrently to a general audience of research-minded chemists and to scientists directly concerned with the subject of the article. In general, the first four or five pages of the manuscript should be directed mainly to the gen-
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V0LUME
15
EDITOR JOSEPH F. BUNNETT ASSOCIATE EDITORS Joel E. Keizer John E. McMurry EDITORIAL ADVISORY BOARD Fred Basolo R. Stephen Berry Michel Boudart Maurice M. Bursey Edward A. Collins John T. Gerig Jenny P. Glusker Kendall N. Houk Jay K. Kochi Maurice M. Kreevoy Theodore Kuwana Ronald N. McElhaney Eva L. Menger Kurt Mislow John C. Polanyi Alexander Rich Anthony M. Trozzolo Gene G. Wubbels Published by the AMERICAN CHEMICAL SOCIETY 1155 16th Street, N.W. Washington, D.C. 20036 BOOKS AND JOURNALS DIVISION D. H. Michael Bowen, Director Journals Department: Charles R. Bertsch, Head; Marianne C. Brogan, Associate Head; Mary E. Scanlan, Assistant Manager Marketing and Sales Department: Claud K. Robinson, Head Production Department: Elmer M. Pusey, Jr., Head Research and Development Department: Seldon W. Terrant, Head The American Chemical Society and its editors assume no responsibility for the statements and opinions advanced by contributors. Views expressed in the editorials are those of the writers and do not necessarily represent the official position of the American Chemical Society.
NUMBER 8
AUGUST,
1982
Data Banks on X-ray Crystallographic Results: Research Tools for Chemists A wealth of information on molecular structure and conformation may be obtained from X-ray diffraction analyses of crystals. Through the years the results of thousands of crystal structure determinations of salts, organic compounds, inorganic complexes, and macromolecules have appeared in the pages of the Journal of the American Chemical Society, Acta Crystallographica, Inorganic Chemistry, and many other relevant journals. It seems almost impossible to keep up with the yearly explosion of such information. But the time has come that such experimental data can be used as a research tool, and chemists should be made more aware of this. Published structural data are now available to the international chemical community on magnetic tape, ready for computer access. There are severaljnajor files that contain structural information. The Cambridge Crystallographic Data File prepared in Cambridge, U.K., under the direction of Dr. Olga Kennard, and updated several times a year, covers small to medium-sized organic molecules. The Inorganic Crystal Structure Database, organized by Dr. I. D. Brown in Hamilton, Ontario, Canada, and Dr. G. Bergerhoff in Bonn, Germany, covers inorganic structures and complements the Cambridge File. The Metal Data File, organized by Dr. L. D. Calvert in Ottawa, Canada, covers intermetallic compounds. Macromolecular structures are listed in the Protein Data Bank, maintained at Brookhaven National Laboratory in the U.S.A. It contains coordinates at various stages of refinement for proteins and, recently, nucleic acid portions (such as the dodecamer and Z-DNA portions studied by Dickerson and Rich). The scientific community owes a debt of gratitude to the early data gatherers who started preparing data banks before the days of automatic diffractometry when there were not so many crystal structures being determined per year. Their work provided the bases for the present files, and the philosophies of the preparation and maintenance of these files had been worked out before the avalanche of structural information deluged us. What can be done with these data? The answer is that the chemist can ask some general structural questions and survey the literature with great ease to obtain the information he needs. For example, for the Cambridge Data File such analyses have been pioneered by Drs. Stephen R. Wilson and John C. Huffman (J. Org. Chem. 1980,45, 560-566) who showed how the data could be used in studies of transition-state structures, conformational analyses, and structure/activity relationships. Such analyses follow earlier studies by Drs. J. D. Dunitz, H. B. Burgi, and P. Murray-Rust who demonstrated the three-dimensional chemical reaction pathways of several reactions such as the nucleophilic displacement reaction at a tetrahedrally coordinated atom (with a trigonal-bipyramidal transition state), removal of a ligand with its electron pair from a tetrahedral molecule to give a three-coordinated trigonal planar structure, and nucleophilic addition to a carbonyl groups. The Inorganic Data File is full of information on cation coordination geometry that can be used, for example, to analyze the relative charges on atoms in the coordination sphere using recent versions of the ideas originally put forward by Linus Pauling. Data from the Protein Data Bank may be used, if a graphics system is available, to display and visually examine a macromolecule and to make deductions about its active site and possible location of substrates and inhibitors, about chain folding and homology with related enzymes, and on the structural effects of substitutions in the macromolecule or the molecules they interact with. Jenny P. Glusker The Institute for Cancer Research Philadelphia, Pennsylvania
