Computer based chemical searches

The E-state indices may define chemical spaces that are relevant in similarity/ diversity search in chemical databases. This similarity search is based on atom-type E-state indices computed for the query molecule [55]. Each E-state index is converted to a z score, Z =(% -p )/0 , where is the ith E-state atomic index, p is its mean and O is its standard deviation in the entire database. The similarity was computed with the EucHdean distance and with the cosine index and the database used was the Pomona MedChem database, which contains 21000 chemicals. Tests performed for the antiinflamatory drug prednisone and the antimalarial dmg mefloquine as query molecules demonstrated that the chemicals space defined by E-state indices is efficient in identifying similar compounds from drug and drug-tike databases. 

This review describes the current status of silenes (silaethylenes, silaethenes), molecules which contain a silicon-carbon double bond. The heart of the material is derived from a computer-based search of the literature which we believe reports all silenes that have been described to date, either as isolated species, chemically trapped species, proposed intermediates (in reactions where some experimental evidence has been provided), or as the result of molecular orbital calculations. Ionized species... 

If the laboratory worker does not know of a reference to the preparation of a commercially available substance, he may be able to make a reasonable guess at the synthetic method used from published laboratory syntheses. This information, in turn, can simplify the necessary purification steps by suggesting probable contaminants. However, for other than macromolecules it is important that at least the NMR and IR spectra of the substance be measured. These measurements require no more than two to three milligrams (which are recoverable) of material and provides a considerable amount of information about the substance. Three volumes on the NMR spectra [C.J.Pouchert and J.Behnke, The Aldrich Library of C and FT-NMR Spectra, Vols 1—3, Aldrich Chemical Co., Inc, Milwaukee, Wl, 1993], and one on the infrared spectra [C.J.Pouchert, The Aldrich Library of FT-IR Spectra, 3nd ed, Aldrich Chemical Co., Milwaukee, Wl, 7959], as well as computer software [FT-IR Peak-search Data Base and Software, for Apple HE, IIC and II Plus computers and for IBM PC computers, Nicholet Instruments, Madison, Wl, 1984] contain data for all the compounds in the Aldrich catalogue and are extremely useful for identifying compounds and impurities. If the material appears to have several impurities these spectra should be followed by examination of their chromatographic properties and spot tests. Purification methods can then be devised to remove these impurities, and a monitoring method will have already been established. 

Algorithm development in the areas of computer editing, data base management, sorting, computer-based composition, and text searching have been critical to the overall development of computer-based primary and secondary publications systems and text search services. Results of these developments are illustrated in the computer-based information system used at Chemical Abstracts Service (CAS) [ 1]. Lynch [2J describes principles and techniques for the computer-based information services and... 

Chemical Titles is a computer-produced list of titles of chemical papers arranged by keywords (KWIC, keyword in context), and produced by Chemical Abstracts Services. The titles appear so that the keywords are listed in the center of the column. It is based on the contents pages of some 700 journals abstracted in Chemical Abstracts, and appears twice monthly. For the most efficient use, a list of keywords is compiled, and the availability of this service on magnetic tape means that computer-based searches of these titles can be made. 

Graf W, Kaindl HK, Kniess H, Schmidt B, Warszawski R. Substructure retrieval by means of the BASIC fragment search dictionary based on the CAS Chemical Registry III system. J Chem Inf Comput Sci 1979 19 51-55. 

Computer-based chemical information systems are now widely used for the storage and retrieval of chemical structure information. Efficient searching algorithms are available which allow structure-based searches to be carried out on databases containing many thousands, or even millions, of chemical compounds. In addition, the ease with which machine-readable structural data can be manipulated has led to a wide range of related activities, such as computer-aided s)uithesis design and studies of quantitative structure-activity relationships (QSAR). ... 

The computer program ELBT of the CD version of this book permits the retrieval of data tables using any single or combined search criterion based on chemical system (a single component or the binary mixture), the vapor-liquid equilibrium property type, and/or the reference (authors, original source of data, and/or year range)... 

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