M. Schiltz et al., ON THE PREPARATION AND X-RAY DATA-COLLECTION OF ISOMORPHOUS XENON DERIVATIVES, Journal of applied crystallography, 27, 1994, pp. 950-960
A simple method for the preparation of isomorphous xenon derivatives i
s presented. A device has been designed that allows diffraction studie
s on protein crystals under xenon gas pressures up to 50 x 10(5) Pa. C
rystal mounting and X-ray data collection do not significantly differ
from standard techniques. Tests carried out on crystals of the protein
porcine pancreatic elastase reveal a single xenon binding site with h
igh occupancy at a pressure of 8 x 10(5) Pa. Xenon binding to several
other crystallized proteins has also been investigated and results ind
icate that the method is generally applicable. Time-resolved studies s
how that, at 297 K, xenon binding is essentially completed within a fe
w minutes. At pressures above 10(6) Pa, successful data collection is
hampered by X-ray absorption and by the formation of xenon hydrate. Ab
sorption can be reduced by using short-wavelength radiation and by mou
nting crystals in small capillaries. To circumvent xenon hydrate forma
tion, higher working temperatures and the use of cryoprotective mother
liquors are advocated.