DARC system

Description, Acquisition, Retrieval, and Correlation File. This is the only other pubhc substmcture search system, apart from CAS Online, that provides full access to the CAS Chemical Registry File. The DARC file, commercially available on-line from Telesystems-Questel, offered the first pubhc on-line implementation of substmctural searching of the CAS Chemical Registry System. The advantages and disadvantages of the CAS Online and DARC systems have been discussed (49). 

Markush DARC system, 18 212, 230, 245 Markush structures, 18 206 Markush TOPFRAG programs, 18 226 Marl, 15 28... 

Dubois, J. E., "DARC System in Chemistry," in Computer Representations and Manipulation of Chemical Information, ed. 

Computer-aided structure elucidation (CASE) has been developed over a period of 30 years. Several major projects that were initiated and carried out during this time consist, in the main, of interdisciplinary efforts toward the automatic solution of problems arising from the everyday practice of chemists. The DARC system of Dubois et the Heuristic DENDRAL project developed at Stanford University, and the CHEMICS system of Sasaki et as well as the developments of... 

The method calls for a combination of the DARC system (Description, Acquisition, Retrieval and Computer-aided design) and the PELCO procedure (Perturbation of an Environment Limited Concentric and Ordered). 

Dubois, J.-E. and Sobel, Y. (1985). DARC System for Documentation and Artificial Intelligence in Chemistry. J.Chem.lnf.Comput.Sci.,25, 326-335. 

PharmSearch. Institut National de Propriete Industrielle, Paris. Pharmaceutical patents indexed by INPI, the French Patent Office, with chemical structures searchable in the Mar-kush DARC system on Questel-Orbit. Abstracts, bibliographic information, and proprietary indexing from one patent per family. PharmSearch shares the topological chemical structure... 

The method is based on a combination of the DARC system (Description, Acquisition, Retrieval and Computer-aided design) and the PELCO (Perturbation of an Environment Limited Concentric and Ordered) procedure. Moreover, it accounts for the simultaneous representation of all the data set compounds and the population of the compounds structurally contained in them the data set compounds, which are those compounds for which a molecular property has been experimentally evaluated, generate an ordered multidimensional space that constitutes a —> hyperstructure. 

Dubois, J.-E., Laurent, D. and Aranda, A. (1973a) DARC system. XVI. Theory of topology-information. I. Method for the perturbation of ordered, concentric, limited environments (PELCO)./. Chim. Phys. Phys-Chim. Biol, 70, 1608-1615. 

Dubois, J.-E., Panaye, A. and Attias, R. (1987) DARC system notions of defined and generic substructures. Filiation and coding of FREE substructure (SS) classes./. Chem. Inf. Comput. Sci, 27, 74-82. 

Dubois JE, Sobel Y. DARC system for documentation and artificial intelligence in chemistry. J Chem Inf Comput Sci 1985 25 326-333. 

A new generation of multiparameter correlations of hi technological importance is presented in the comprehensive work of Dubois on the DARC system and... 

Several groups have a special interest in chemical information handling, in particular the subjects of chemical structure storage and computer-assisted chemical synthesis. The most remarkable French contribution in this area is the DARC system developed by Jacques-fimile Dubois for molecular encoding and chemical information retrieval. ... 

Watson, D. Some Experiences with the DARC System. In Proceedings of the CNA(UK) Seminar on Chemical Structure Searching of the Published Literature Dareshury, UJC., 17-19 March 1980. Chemical Structure Association, 1982. 

The concept of concentric environment has been introduced by Dubois in the DARC system as an alternative to the traditional fragment concept. The radius of perception was two, i.e., the first and the second neighbours of the atom in question were taken into account. Features used for characterisation were the type of the atom, the type of its bonds and the number of neighbours. To limit the number of fragments only the environment of tertiary and quaternary atoms have been used for structure descriptions in the DARC system. 

Whatever the search software offered, however, the database was of utmost importance. The DARC system not only offered a means to search generic structures in the short term, it also offered a way to record all of the information about structures found in patents, through a new and flexible input system. This capability was of incredible import to Derwent we could build a database that would not only serve the users today, but in future could be of more utility as search software was further developed. As opposed to the fragmentation code, there should never be a question of time-ranging. Moreover, though we assume that Markush DARC is a system not only of today but of tomorrow, we are building a database that can be converted and adapted to other search systems that may be offered by other organisations. 

Markush DARC represents a system from which we can progress. Derwent and INPI have built in essential information into the database that allows for future expansion of capabilities. These capabilities include generic search, translation of generic expressions to specifics and specifics to generic expressions, and sophisticated limitations in search results. Derwent believes that the Markush DARC system should be viewed as not only a product of today, but also as an embryonic representation of what the future holds. 

A more exhaustive search for cognate substructures can be carried out with the CAS Online System, where more than 600000 substances are searchable through Chemical Abstracts, in France the DARC system is used similarly. In this approach, some biological data will be delivered directly, but more can often be obtained by inserting the CAS number of the substance into the US National Institute of Health s MEDLARS system (available without charge in many countries through local Departments of Health). 

CAS uses an extension to the CIP system to denote the configuration of mononuclear coordination compounds. The stereodescriptors are composed of a system indicator (e.g., OC-6 for octahedral), a geometry label, and potentially a chirality symbol. The geometry label is assigned on the basis of CIP priorities and the chirality symbol describes the handedness of the ligand arrangement with respect to some principle axis through the center. The DARC system also uses priorities (not based on CIP) and a method has been proposed to apply them to the stereochemistry of coordination compounds, ... 

Apart from MARPAT there is another database describing Markush structures, it is the Markush system of Derwent in combination with the database PHARMPAT of the Institut National de la Propriete, which is offered exclusively by the host QUESTEL, where it is searchable using the Markush-Darc system. Markush-Darc is a joint venture by Derwent Publications Ltd., the Institut National de la Propriete Industrielle and QUESTEL. It has been available since 1989 online and contains two files ... 

QUESTEL and STN are the only hosts providing the graphic structure search using the Generic DARC System. Under the same command mode Derwent s Markush Dare file, containing the Markush structures is available. Regrettably, there is no nomenclature file text on QUESTEL which would allow searches for substance names und molecular formulae. 

DARC CHEMLINK (from Telesystemes) is a program which allows offline formulation of queries for submission to DARC data bases. Its structure drawing interface is intentionally very similar to that of the DARC system online. 

Some useful interfaces to the DARC system are described in Chapter 10. 

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