User advice on what type of samples to bring
The general rule is that cleaner absorption spectra are obtained
from thin crystals: a feature of the high optical densities often
encountered in protein and DNA crystals.
This of course is highly dependant on the composition of your
crystals and also which region of the UV/Vis spectrum you wish to
monitor.
If your crystal contains a cofactor with a large exctinction
coefficient you may have difficulties monitoring at the peak absorption
wavelength.
However we can routinely collect high quality spectra up to 2.5OD units
therefore in many cases this problem can be overcome using thin
crystals or thin parts of wedge shaped crystals. Such crystals may not
yield the best X-ray diffraction but it should be stressed that dose
measurments can be scaled up and therefore collection strategies can be
designed for large crystals using the spectroscopic data collected from
thin crystals.
The more information you bring to the experiment the better. If
possible, bring hardcopies of reference spectra measured in solution.
This will allow us to quickly optimise the light source and detector
for your wavelength range of interest.
A recommended strategy, and something that will aid your beamtime application, is to perform some tests offline at the
Cryobench Laboratory.
Facilities exist to perform a range of absorption, fluorescence and
other advanced spectroscopic techniques such as Raman on both solutions
and crystals.
