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Challenges of sulfur SAD phasing as a routine method in macromolecular crystallography

Doutch, James and Hough, Michael A and Hasnain, S Samar and Strange, Richard W (2012) 'Challenges of sulfur SAD phasing as a routine method in macromolecular crystallography.' Journal of Synchrotron Radiation, 19 (1). pp. 19-29. ISSN 0909-0495

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<jats:p>The sulfur SAD phasing method allows the determination of protein structures<jats:italic>de novo</jats:italic>without reference to derivatives such as Se-methionine. The feasibility for routine automated sulfur SAD phasing using a number of current protein crystallography beamlines at several synchrotrons was examined using crystals of trimeric<jats:italic>Achromobacter cycloclastes</jats:italic>nitrite reductase (<jats:italic>Ac</jats:italic>NiR), which contains a near average proportion of sulfur-containing residues and two Cu atoms per subunit. Experiments using X-ray wavelengths in the range 1.9–2.4 Å show that we are not yet at the level where sulfur SAD is routinely successful for<jats:italic>automated</jats:italic>structure solution and model building using existing beamlines and current software tools. On the other hand, experiments using the shortest X-ray wavelengths available on existing beamlines could be routinely exploited to solve and produce unbiased structural models using the similarly weak anomalous scattering signals from the intrinsic metal atoms in proteins. The comparison of long-wavelength phasing (the Bijvoet ratio for nine S atoms and two Cu atoms is ∼1.25% at ∼2 Å) and copper phasing (the Bijvoet ratio for two Cu atoms is 0.81% at ∼0.75 Å) for<jats:italic>Ac</jats:italic>NiR suggests that lower data multiplicity than is currently required for success should in general be possible for sulfur phasing if appropriate improvements to beamlines and data collection strategies can be implemented.</jats:p>

Item Type: Article
Uncontrolled Keywords: single-wavelength anomalous diffraction; automated S-SAD; data redundancy; Cu-SAD; phasing; radiation damage
Subjects: Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Science and Health
Faculty of Science and Health > Life Sciences, School of
SWORD Depositor: Elements
Depositing User: Elements
Date Deposited: 12 Jan 2012 08:16
Last Modified: 15 Jan 2022 00:45

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