Substructure CHEMLINE

CHEMLINE (CHEMical dictionary on-LINE) is a file of chemical descriptors created by NLM s Toxicology Information Program in collaboration with Chemical Abstracts Service (CAS). This file contains nearly 500,000 chemical substance names representing over 246,000 unique substances. Because of CHEMLINE s unique file design, it has capabilities which support both full structure and substructure searching. 

The next set of fields (NR through CL) in this record contains ring information. Since about 80% of the substances within CHEMLINE contain ring systems, one can see the Importance of Incorporating this Information into a chemical structure search system, especially for substructure searching. 

The following sections are provided to demonstrate several approaches to substructure searching in CHEMLINE (3-6). Figure 6 shows the structural diagram of Leptophos and the characteristics of a substructure search query based on the chemical structure of this insecticide. 

A logical approach to this query would be to search CHEMLINE for the given common name, PRINT the systematic chemical name and select name fragments that correspond to the desired substructure. This is illustrated in the first portion of Figure 7. 

The next example of a CHEMLINE substructure search is for chlorinated dlbenzodloxlns. As seen in Figure 10, this substructure query is derived from the herbicide contaminant Dioxin. The search can be approached without using any chemical nomenclature through use of the Formula Fragment (FF) and ring information fields (Ring Elemental (RE) analysis and Component Line (CL) formula). The search retrieves forty records a few of the chemical names are PRINTed to review the output. 

Since systematic chemical name fragments and molecular formula fragments are also found in the RTECS file, one can use CHEMLINE nomenclatural output to perform a substructure search that is correlated with a biological concept in RTECS. This would obviate the need to carry the chemical identifiers for the forty CHEMLINE records into the RTECS file. 

The National Library of Medicine s (NIH) on-line chemical dictionary file (CHEMLINE) is primarily used to enhance the retrieval of bibliographic Information associated with chemical substances. This discussion demonstrates the utility of CHEMLINE as a mechanism to link chemical substructures to biological data. Search techniques are developed to Integrate classes of structurally related chemicals with toxicity data and information contained in on-line retrieval files such as the Registry of Toxic Effects of Chemical Substances (RTECS) and TOXLINE. 

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