mRuby2 is a monomeric red fluorescent protein with an excitation peak of 559nm and an emission peak of 600nm. It is an artificial derivative of the naturally occurring fluorescent protein encoded by the Entacmaea quadricolor eqFP611 gene, obtained by mutagenesis of mRuby, and its fluorescent properties make it useful as a FRET acceptor for the Clover fluorescent protein. It contains the mutations L15M, I102V, A119V and A131P relative to mRuby (PMID:22961245).