The role of wavelength and source in the search for sulfur-atom positions evaluated in two case studies: lysozyme at room temperature and cryo apocrustacyanin A1

• Published in: Journal of applied crystallography Vol. 37; no. 4; pp. 555 - 564
• Main Authors: Cianci, Michele, Helliwell, John R., Moorcroft, David, Olczak, Andrzej, Raftery, James, Rizkallah, Pierre J.
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England Munksgaard International Publishers 01.08.2004; Blackwell; Blackwell Publishing Ltd
• Subjects: Analytical, structural and metabolic biochemistry; apocrustacyanin A1; Biological and medical sciences; Biological compounds; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; lysozyme; macromolecular crystallography; Miscellaneous; Organic compounds; Physics; protein crystallography; Proteins; radiation damage; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; sulfur atom location; wavelength choice; Enzyme; Physical radiation effects; Experimental study; Protein; Apocrustacyanin; Reflection spectrum; Macromolecule; Glycosidases; Hydrolases; Anomaly; O-Glycosidases; Lysozyme; Synchrotron radiation; Organic compounds; Damaging; Crystalline structure
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S0021889804010052

Synchrotron radiation beamlines offer automated data collection with faster and larger detectors, a choice of wavelength(s), intense beams and fine collimation. An increasing output of protein crystal structures sustains an interest in streamlining data collection protocols. Thus, more and more investigators are looking into the use of the anomalous signal from sulfur to obtain initial phase information for medium‐size proteins. This type of experiment ideally requires the use of synchrotron radiation, softer X‐rays and cryocooling of the sample. Here the results are reported of an investigation into locating the weak, i.e. sulfur, anomalous scatterers in lysozyme using rotating anode or synchrotron radiation data recorded at room temperature. It was indeed possible to locate the sulfur atoms from a lysozyme crystal at room temperature. Accurate selection of images during scaling was needed where radiation damage effects were detected. Most interestingly, comparisons are provided of high‐redundancy data sets recorded with synchrotron radiation at λ = 2.0 and 1.488 Å, and with Cu Kα and Mo Kα radiation. Apocrustacyanin A1 was also investigated; from the results of a very high redundancy data collection using softer synchrotron X‐rays and a cryo‐cooled crystal, it was possible to find the sulfur atoms.