Dear Sebastiano,
why not have a look at http://sis.niaid.nih.gov/cgi-bin/heavyatom_reactivity.cgi. A reprint of the original paper can be found at http://sis.niaid.nih.gov/pub_pdf/Agniswamy-et-al-2008.pdf We did not specifically look at Bis-Tris Propane but did look at Tris pH 8.5 and Hepes pH 8. We certainly found greater reactivity in Hepes buffer with a number of mercury compounds and perhaps if your crystals can survive, switching to this buffer for the heavy atom soaking experiments should improve reactivity. I would definitely recommend short soaks (2-10 min) with high compound concentration (1-10 mM). Due to your limited crystal supply, the most reactive compounds we have found are in order. Ranking of the most reactive compounds % Derivitization Ethyl mercury (II) phosphate 69.4 Methyl mercury (II) Acetate 66.6 Sodium tetrachloro aurate 61.1 Potassium tetrabromo palatinate 55.5 Potassium tetrachloro aurate 52.7 Ammonium tetrachloro palatinate 50.0 Gold (III) chloride 47.2 Diamino platinum dinitrate 47.2 Thiomersal 47.2 Mercury (II) acetate 47.2 PCMBS 47.2 Potassium tetrachloro palatinate 44.4 Potassium tetranitro palatinate 44.4 Lead acetate 43.3 Potassium hexabromo palatinate 41.7 Methyl mercury (II) chloride 38.8 Mersalyl 38.8 Mercury(II)bromide 36.1 Mercury(II)cyanide 33.3 Gold chloride 33.3 Platinum potassium thiocyanate 33.3 Lead nitrate 33.3 Yours, Gordon M. Gordon Joyce, Visiting Fellow, Structural Immunology Section, Laboratory of Immunogenetics, NIH/NIAID, 12441 Parklawn Drive, Rockville, MD 20851 Phone: 301 594 0242 Office 301 496 3792 Lab
