title: Generating isomorphous heavy-atom derivatives by a quick-soak method. Part I: test cases.
abstract: Screening for heavy-atom derivatives remains a time-consuming and cumbersome process that often results in non-isomorphous derivatives whose phases cannot be combined. Using lysozyme and FcgammaRIII receptor crystals as test cases, an improved soaking method for the generation of conventional heavy-atom derivatives has been developed. The method is based on soaking crystals in heavy-atom compounds for a very brief time at near-saturation concentrations. Compared with the current heavy-atom soaking method, which often takes days to achieve a derivatization, the quick-soak method completes a derivatization within 10 min to 2 h. The bound heavy-atom sites display higher peak heights from quick soaks than from overnight soaks in all cases tested. The quick-soak derivatives also preserved native-like diffraction resolution and data quality that was better than the prolonged-soak derivatives. Furthermore, derivatives generated by brief soaks are more isomorphous to the native than those generated by overnight soaks. Short soaks not only increase the likelihood of success in heavy-atom screening by reducing the pitfalls associated with prolonged soaks, such as lack of isomorphism and overall lattice disorder, but also have the potential to transform a time-consuming derivative screening into an 'on-the-fly' real-time derivatization process.
authors.affiliation: Structural Biology Section, Laboratory of Immunogenetics, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12441 Parklawn Drive, Rockville, MD 20852, USA. psun@nih.gov
authors.forename: Peter D
authors.initials: PD
authors.lastname: Sun
authors.forename: Sergei
authors.initials: S
authors.lastname: Radaev
authors.forename: Michael
authors.initials: M
authors.lastname: Kattah
mesh_terms: D000818:Animals; D001665:Binding Sites; D002645:Chickens; D018360:Crystallography, X-Ray / Q000295:instrumentation* / Q000379:methods*; D005583:Fourier Analysis; D017612:Gold Compounds / Q000737:chemistry; D007700:Kinetics; D013058:Mass Spectrometry; D008627:Mercuric Chloride / Q000737:chemistry; D019216:Metals, Heavy / Q000737:chemistry*; D008958:Models, Molecular; D009113:Muramidase / Q000737:chemistry*; D017671:Platinum Compounds / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D015202:Protein Engineering; D017452:Receptors, IgG / Q000737:chemistry*; D013997:Time Factors
chemical_list: D017612:Gold Compounds; D019216:Metals, Heavy; D017671:Platinum Compounds; D017680:Potassium Compounds; D017452:Receptors, IgG; C030173:platinum chloride; D008627:Mercuric Chloride; D009113:Muramidase