Could you try a quick (10-15s) halide soak (Iodine) with e.g. 1M NaI? Tim -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen
GPG Key ID = A46BEE1A On Fri, 15 Feb 2008, john peter wrote:
Dear Folks, I recently grew crystals in the presence of 100 mM Imidazole pH 8.0 and 1 M Ammonium Phosphate. The protein was in 25 mM Hepes pH 7.4, 10 mM EDTA, 10 mM EGTA and 100 mM NaCl. I like to make heavy atom derivatives with Hg, Pt, Sm, Au and Pb compounds. I think the imidazole will interfere with Pt. EDTA and EGTA may also interfere with cations. However I'm not sure about the effect of phosphate. I tried to transfer the crystal to PEGs by gradually decreasing the AmPO4 concentration and increasing the PEG concentration, but the crystals deteriorate. I'm wondering what successful strategy people have employed to make good heavy atom derivatives when the mother liquor has salt as the major precipitant. All suggestions, tips are greatly appreciated. Thanks a lot. John
