How specific is the detection of endogenous chromophores? They report that 60nm is the absolute detection limit, but this is for a pure chromophore in water. In real cells there will be many other endogenous chromophores at various concentrations. For example, endogenous background fluorescence of flavins is often easily seen when imaging at CFP wavelenghts. Watt Webb has been imaging those types of chromophores for years. The intersection of both a preferred excitation wavelengh and a preferred stimulated emission wavelength will provide some selectivity, but I suspect this will be most useful for imaging the distribution of fairly highly expressed chromophores in vivo. Distinguishing chromophores with highly overlapping spectra may not be possible. Of course, many, many proteins don’t have distinctive chromophores (tyrosine does not count!) built in to them, so GFP won’t be out of work any time soon. However, this stimulated emission imaging doesn’t require transgenic or small molecule labeling, so it could potentially allow imaging in humans.
Thanks goes to Reporter Gene for the story tip.`