The creation of a database of odorous compounds focused on molecular rigidity and analysis of the molecular features of the compounds in the database

It is important to select odorous molecules for experiments on olfaction and for the development of an electronic nose. Odorous molecules having a small number of conformers, namely structurally rigid molecules, are assumed to interact with a small number of types of olfactory receptor proteins or to interact with the proteins in a simpler manner than that of fairly flexible molecules. Focusing on the rigidity of molecular structures, we collected 287 odorous molecules from data sources, which included 1205 chemicals in total and a database of the 287 odorous molecules (DB_odMOL) was created using CS ChemFinder Pro (version 5.0). The logarithmic value of the octanol/water partition coefficient (log P) and melting point, boiling point and vapour pressure of the molecules were estimated using CS Chem3D Pro. The database DB_odMOL accumulates these estimated data in addition to literature values for odour quality, odour detection thresholds and the safety of molecules. The rigidity of the 287 molecules was further analysed by conformational analysis performed by molecular mechanics using Conformer in CS Chem3D Pro (version 5) and 72 rigid odorous molecules were selected. The 287 molecules were also analysed based on atomic composition, substructure and molecular size. Sixty-two odorous molecules among the 72 rigid odorous molecules were further selected based on their atomic composition. The 62 rigid molecules with simple atomic composition that were finally selected should be useful for researchers in choosing odorous molecules for the study of olfaction, including the fields of molecular biology, physiology, structure-odour relationships and other fields of the study concerning odour.