Chemical Connectivity Searching

The chemical connectivity tables are, of course, a formalized representation of 2D chemistry, and, in some situations, rules must be applied in creating the table. These rules must be known to the user when a chemical substructure search query is being formulated and are further discussed in Section 3.7.4. 

Ptaquiloside is not the only illudane present in PteridiumThe clear chemical connection between ptaquiloside and pterosin B, carries within the suggestion that at least some of the myriad indanones that bracken synthesizes is the result of the biosynthetic progress from ptaquiloside-like precursors. Supporting evidence was drawn from the fact that ptaquiloside and pterosin B concentrations vary simultaneously with aging of the fronds [124,218], With this idea in mind, Castillo and coworkers pursued the search of additional illudanes in this fern. 

ConQuest provides search, retrieval, and display facilities for the CSDJ Individual queries can be set up to interrogate the bibliographic, chemical text, and crystal data fields listed in Table 2, and, in particular, the program provides extensive graphical facilities for the definition of 2D and 3D substructure searches. The 2D searches interrogate the chemical connection tables alone, while... 

With the graphical output program in place, it was possible to provide our scientists with the first fruits of the early SOCRATES system graphical structure display at a terminal of compounds from the company files (generated fi om the stored WLN s via connection tables). The next step was to provide a structure match capability. As mentioned earlier, within INDABS there already existed a fast chemical novelty search which employed an index of topological codes. This was easily integrated into SOCRATES to accept graphically drawn structures fi om SENTRY instead of WLN s. 

CHEMICAL CONNECTIONS 20A The Search for Antiviral Drugs 20B DNA Fingerprinting... 

Section 28.2 Chemical Connections The Search for Antiviral Dmgs... 

The earliest system which allowed substructure searching involving chemical connectivity input and structure display, was the National Institutes of Health/ Environmental Protection Agency Chemical Information System, the NIH/EPA CIS 14). Its Structure and Nomenclature Search System (SANSS) eventually allowed access to a large range of public data bases. The system allowed access from teletype terminals and was not graphics-based. 

Structure databases are databases that contain information on chemical structures and compounds. The compounds or structure diagrams are not stored as graphics but are represented as connection tables (see Section 2.4). The information about the structure includes the topological arrangement of atoms and the connection between these atoms. This strategy of storage is different from text files and allows one to search chemical structures in several ways. 

The lUPAC rules are not the only nomenclature system in use today Chemical Abstracts Service sur veys all the worlds leading scientific journals that publish papers relating to chemistry and publishes brief abstracts of those papers The publication Chemical Abstracts and its indexes are absolutely es sential to the practice of chemistry For many years Chemical Abstracts nomenclature was very similar to lUPAC nomenclature but the tremendous explosion of chemical knowledge has required Chemical Abstracts to modify Its nomenclature so that its indexes are better adapted to computerized searching This means that whenever feasible a compound has a sin gle Chemical Abstracts name Unfortunately this Chemical Abstracts name may be different from any of the several lUPAC names In general it is easier to make the mental connection between a chemical structure and its lUPAC name than its Chemical Abstracts name... 

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