Atlas Of Steroid Structure

model. In general, the mean atomic positions and the geometrical parameters calculated from them are more accurate if the more sophisticated anisotropic model has been used for the thermal motion during structure refinement. Low temperature data collection also results in more accurately determined structures. By decreasing the temperature at which data is collected, the intensities and number of data observed is increased. Since hydrogen atoms have only a single electron, they scatter X-rays very weakly, and they can be observed experimentally only if the data are of good quality. Finally, in the absence of systematic errors in data collection or refinement, tae greater the number of observed data relative to the number of independent atoms, the better the atomic resolution will be. Table 1 is a summary of the information used in assessing the reliability of a structure. Neutron diffraction is the result of interaction of atomic nuclei with a neutron beam. The intensi ty of the diffracted beam is not proportional to atomic number. Hydrogen, deuterium, carbon, oxygen and nitrogen scatter neutrons with almost equal intensity. In addition, hydrogen and deuterium scatter out of phase so that they can be distinguished wita high precision. 20-Methyl-5-pregnene-3S,20-diol (PR104N) is the only steroid which has been the subject of a neutron diffraction study. The study was undertaken to examine the stereospecificity of Grignard addition using deuterated reagent. Data were collected at 123°K.

The crystal structure determinations of over 235 natural and synthetic steroid molecules reported from 1945 to 1974 constitute the most detailed block of structural data on any class of biologically active molecules in existence and provide a wealth of raw material concerning molecular con formation and intermolecular interactions ideally suited to the analysis of structure-function correlations. Volumes of physiological data gener ated in studies ranging from simple dose-response characterizations to elegant examination of receptor binding sites make up the functional counterpart to this structural data reservoir. The utilization of these data for purposes of exploring biochemical reactions at the molecular level has been inhibited by lack of communication among structural chemists, bio chemists, and clinicians. The typical non-crystallographer in the fields of biochemistry and endocrinology finds it difficult to interpret structure reports. The molecular features of key importance from his point of view are often omitted, and, although atomic coordinates are usually tabulated, he may be unable to calculate the details which he needs. Structure reports on steroids have often been published in obscure journals and in some cases the paper has been extremely brief and no mention of the biological importance of the material has been made. Lack of uniformity in presen tation of data has also been an impediment to utilization of these data by non-crystallographers. Similarly, the average crystallographer has difficulty assessing data concerning biological activity.

Molecular Structure and Biological Activity of Steroids focuses on the indentification of steroid structural features that control particular biological effects. Steroid geometry plays a critical role in steroid activity; therefore, the results of X-ray crystallographic, NMR spectroscopic, and theoretical studies on structure-activity relationships form an integral part of the book. Well-established observations and proposed models are presented, summarizing knowledge of molecular features (e.g., steroid backbone structures, side-chain constitutions, substitution sites, configurations, hydrogen-bonding patterns) that can affect steroid action. The book also provides overviews about recent progress in various frontier fields of steroid research, including such areas as sex steroids, glucocorticoids, aromatase inhibitors, vitamin D metabolites, brassinosteroids, neuromuscular blocking agents, and cardiotonic steroids. Molecular Structure and Biological Activity of Steroids is a "must-have" resource for biochemists, pharmacologists, endocrinologists, biophysicists, and others actively involved in steroid research.

Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 90 years The Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.

Proceedings of the Fourth International Congress on Hormonal Steroids contains plenary speeches and symposia from the Fourth International Congress on Hormonal Steroids held in Mexico City in September 1974

Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 90 years The Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.

Structure-Based Drug Design brings together scientists working on different aspects of the subject, demonstrating the necessary collaboration and interdisciplinary approach to this complex area. The focus is on X-ray crystallographic and computational approaches. The general aspects of these approaches are introduced in the first six articles. The remaining articles provide examples of the application of X-ray crystallography, molecular modelling, molecular dynamics, QSAR, database analysis, and homology modelling. The papers cover a wealth of interesting problems in the design of new and enhanced pharmaceuticals.