In conclusion, the described spectrophotometer allows one
to collect ¯uorescence emission spectra from protein crystals
with a high sensitivity. Although their information content
generally differ, ¯uorescence spectra often surpass in quality
the corresponding absorption spectra recorded on the same
crystalline sample. Crystals that are optically too dense or too
transparent to provide absorption spectra of any use may still
be amenable to ¯uorescence spectroscopy. A further advantage
of ¯uorescence when the bulk of an opaque sample has to
be probed is that an excitation wavelength remote from the