Mena, M.A., Treynor, T.P., Mayo, S.L., and Daugherty, P.S.
Blue fluorescent proteins with enhanced brightness and photostability from a structurally targeted library.  Nature Biotechnology 24: 1569-71 (2006).

The utility of blue fluorescent protein (BFP) has been limited by its low quantum yield and rapid photobleaching. A library targeting residues neighboring the chromophore yielded a variant with enhanced quantum yield (0.55 versus 0.34), reduced pH sensitivity and a 40-fold increase in photobleaching half-life. This BFP, named Azurite, is well expressed in bacterial and mammalian cells and extends the palette of fluorescent proteins that can be used for imaging.