Dear CCP4BB, Let me introduce our recently published result in Acta D (2012) 68(Pt 9): 1253~1258 entitled "Experimental phasing with zinc anomalous scattering". (Edited by Dr. Manfred S. Weiss and this result is also presented in ECM27, Bergen, Norway in 7th Aug. 2012 by Dr. Sun-Shin Cha)
MAD/SAD are the prevailing methods to determine novel structures. Anomalous scattering of transition metals including selenium, mercury, lead, platinum, and gold is critical for MAD and SAD. Zinc is also a suitable metal for MAD/SAD, considering the fact that structures of proteins with intrinsically-bound zinc are successfully determined by zinc anomalous scattering. However, zinc is not used for structure determination of proteins without zinc-binding sites. We noticed that proteins whose crystals were grown in crystallization reagents containing zinc acetate have zinc ions on their surface. Zinc ions are coordinated by a single amino acid (histidine, aspartate, glutamate, asparagine, or glutamine) and water molecules (or acetate molecules) with a tetrahedral or octahedral geometry, indicating that the surface of any protein can be coated with zinc ions. Based on this observation, we soaked three protein crystals in a zinc-containing solution and solved the structures by SAD, demonstrating the effectiveness of the zinc-coating method for structure determination. We hope that you would share these ideas and get successful results in correspond cases. Please share your comments and advices anytime to Dr. Cha ([email protected]). Yours sincerely, Min-Kyu Kim
