Rap. Nagem et al., Protein crystal structure solution by fast incorporation of negatively andpositively charged anomalous scatterers, ACT CRYST D, 57, 2001, pp. 996-1002
The preparation of derivatives by the traditional methods of soaking is one
of the most time-consuming steps in protein crystal structure solution by
X-ray diffraction techniques. The `quick cryosoaking' procedure for derivat
ization with halides (monovalent anions) offers the possibility of signific
antly speeding up this process [Dauter et al. (2000), Acta Cryst. D56, 232-
237]. In the present work, an extension of this technique is proposed and t
he use of two different classes of compounds (monovalent and polyvalent cat
ions) that can be successfully utilized in the quick cryosoaking procedure
for the derivatization and phasing of protein crystals is described. This a
pproach has been tested on hen egg-white lysozyme and has been successfully
used to solve the structure of a novel trypsin inhibitor. The possibility
of using cations in the fast cryosoaking procedure gives additional flexibi
lity in the process of derivatization and increases the chances of success
in phase determination. This method can be applied to high-throughput cryst
allographic projects.