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David Bradley ISSUE #40
September 2004

That INChI Feeling

Steve Heller ??
Steve Heller ?

Over the years, IUPAC names have become increasingly cumbersome. But, Dmitrii Tchekhovskoi, Steve Stein, and Steve Heller of the National Institute of Standards and Technology (NIST) have worked to develop a means for identifying chemical structures on a computer without having to work out a complex, standard nomenclature for each one. The RSC's Alan McNaught heads the IUPAC Task Group for the project, while Reactive Reports publisher ACD/Labs has incorporated the concept into their ACD/ChemSketch structure drawing program.The resulting IUPAC-NIST Chemical Identifier (INChI) could revolutionize chemical information retrieval, cheminformatics, and data mining.

?? INChI in action on ChemSketch. Click image to magnify
?
INChI in action on ChemSketch. Click image to magnify
? Screengrab of INChI in action on ChemSketch (Images by David Bradley)

The chemical structure of a compound is its only true identifier, according to the developers of INChI; however, structures are not unique or convenient for computers. The INChI team, building on Heller's original idea, has found an algorithm that converts any structure using its atom connection table into a unique string of characters.

The latest version of INChI now not only handles organic, covalent structures but also inorganic and organometallic compounds and is now available.

In practice, a user will simply draw a compound's structure in a package, such as ACD/ChemSketch, and the built-in INChI component will convert it to a unique identifier. The string could, in theory, be converted back to a structure. "We will all reap the benefits of a generally accepted computer convention for uniquely representing and communicating the identity of any chemical substance," McNaught told Reactive Reports.

http://hellers.com/~steve/

http://www.iupac.org/organ/members/m/mcnaught.html

Test programs (for Microsoft Windows), documentation and sample structure files are available for download at: http://chemdata.nist.gov/IChI/INChIv11b.zip