N-(3-Oxopentanoyl)-L-homoserine lactone is an autoinducer, a kind of chemical signal molecule which passively diffuses across the bacterial envelope and accumulates intracellularly at high bacterial densities. It may bind to a protein related to the LuxR protein of V. fischeri and causes cell density-dependent gene expression. N-(3-Oxopentanoyl)-L-homoserine can be used for research of quorum sensing^[1].