You may also wish to take a look in Dauter and Nagem's quick cryo soaking for introducing anomalous scattering.
1. Acta Crystallogr D Biol Crystallogr. 2001 Jul;57(Pt 7):996-1002. 2. Methods Enzymol. 2003;374:120-37. 3. Acta Crystallogr D Biol Crystallogr. 2005 Aug;61(Pt 8):1022-30 HTH [ ]s --alessandro