Anomalous scattering of X-rays by cesium and cobalt measured with synchrotron radiation

Templeton, David H.; Templeton, L. K.; Phillips, J. C.; Hodgson, K. O.

doi:10.1107/s0567739480000940

Cited by 103 publications

(59 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hence, for a plane-polarized beam, the polarization factor is independent of the polarization effects of the pre-specimen reflectors with the important consequence that the state of perfection of crystal monochromators used in the experiment need no longer be of concern (Vincent & Flack, 1980). Moreover, when Pm --0° in (7)Pm = 1, implying no correction for polarization effects whatsoever (as realized by Templeton, Templeton, Philips & Hodgson, 1980; indeed it is the ideal case). Similarly, when Pm ----90°, Pm = cos 2 28 m, implying a correction equal to 1/cos 2 28 m. Other aspects of these two cases have been discussed by Vincent & Flack (1980).…”

Section: Plane-polarized Beammentioning

confidence: 96%

The polarization factor for a repeatedly reflected X-ray beam: special cases

Vincent¹

1982

Acta Cryst Sect A

View full text Add to dashboard Cite

ConclusionOur X-ray investigations on a-CuNSal have shown a reversible and continuous structural phase transition from a commensurate to an incommensurate orthorhombic phase at T i = 303 K and a reversible first-order phase transition into a monoclinic commensurate phase at 241 K. There also exists an intense temperature-dependent diffuse scattering along a* and we assume that it is caused by dynamic atomic movements associated with the phase transition at T r Within the incommensurate phase we observe a pronounced diffuse scattering around the satellite reflections which is explained by phase fluctuations of the modulation wave. The results are discussed within the frame of a simple model assuming equal amplitudes of the modulation wave for all atoms of the chelate molecule.At the moment refinements of the structures within the three phases are performed and we hope that these investigations will supply important information on the dynamic processes at the phase transition. AbstractA method for determining the polarization factor for a repeatedly reflected X-ray beam is described. It is shown that, provided the relative orientations of the pre-specimen reflectors are restricted to special geometries (the usual cases), the appropriate expression for an unpolarized beam reflected m times can be simply derived. The treatment is extended to a plane-polarized beam, resulting in an expression dependent on polarization effects from the specimen alone and hence independent of the state of perfection of crystal monochromators. The latter expression may have some relevance to experiments performed with synchrotron radiation.Many of the techniques used today for measuring X-ray diffraction data have as an integral part of their instrumentation a system of pre-reflectors, reflecting the beam before diffraction by the specimen takes place. Such systems may include one or more crystal monochromators and/or focusing mirrors, usually serving either to select a particular wavelength of radiation or to produce a convergent beam of X-rays. The common feature of most -if not all -these arrangements is the relative orientations of the prespecimen reflectors with respect to one another and, in some cases, to the specimen itself. These geometries are restricted to two types: those in which the diffraction plane (the plane containing the incident and reflected beams) of the ith reflector is parallel to the diffraction plane of the first reflector (p = 0 ° geometry), and those in which the diffraction planes of the first and /th reflectors are perpendicular to each other (p = 90 ° geometry). A general formula for the polarization factor for a system of one monochromator plus specimen has been 0567-7394/82/040510-03501.00(c~ 1982 International Union of Crystallography

show abstract

Section: Plane-polarized Beammentioning

confidence: 96%

The polarization factor for a repeatedly reflected X-ray beam: special cases

Vincent¹

1982

Acta Cryst Sect A

View full text Add to dashboard Cite

show abstract

“…We have recently solved the structure of a trimeric haemerythrin at 5.5 Å resolution using Fe-resolved anomalous phasing followed by molecular averaging for phase refinement (J. L. Smith and W. A. H., unpublished). The possibility of performing multi-wavelength experiments at synchrotrons [35][36][37] enhances the promise for anomalous-scattering applications.…”

Section: Prospective Applicationsmentioning

confidence: 99%

Structure of the hydrophobic protein crambin determined directly from the anomalous scattering of sulphur

Hendrickson

Teeter

1981

Nature

653

512

View full text Add to dashboard Cite

The highly ordered crystal structure of crambin has been solved at 1.5 Å resolution directly from the diffraction data of a native crystal at a wavelength remote from the sulphur absorption edge. The molecule has three disulphide bridges among its 46 amino acid residues, of which 46% are in helices and 17% are in a β-sheet. Crambin is shown to be an amphipathic protein, inasmuch as its six charged groups are segregated from hydrophobic surface elements. Phasing methods used here will also apply elsewhere.Bijvoet's observation 1 that anomalous scattering might aid in solving the phase problem has had many implications 2 , including suggestions that departures from Friedel's law of diffraction symmetry might suffice to determine directly the atomic structures of crystals containing heavy atoms [3][4][5] . Anomalous-scattering methods have also been widely used in protein crystallography [6][7][8][9][10][11] , particularly as an adjunct to isomorphous-replacement phasing. We have now combined elements from these two traditions to solve the structure of crambin by exploiting the anomalous scattering of sulphur atoms at a single wavelength (1.54 Å of CuKα) far removed from the absorption edge of sulphur (5.02 Å).Crambin is a small protein found in the embryonic tissue (cotyledons and hypocotyledons) of seeds from Crambe abyssinica, a relative of mustard and rape commonly known as Abyssinian cabbage. It is hydrophobic in that organic solvents are required to solubilize it, Van Etten et al. 12 characterized crambin after noticing that crystals formed during evaporation of an aqueous acetone extract of defatted seed meal. The remarkable crystalline order observed by Teeter for this protein (strong diffraction from spacings <0.88 Å) 13 correlates well with the unprecedented structural stability seen in solution by Llinás et al. 14 using NMR spectroscopy. The function of crambin is not known. However, the recently completed chemical sequence 15 reveals an unmistakable homology with the plant toxins purothionin 16 and viscotoxin 17 . Crambin itself is not toxic when fed to rats 18 .We set out to solve the crystal structure of crambin in view of its exceptional potential for providing detailed structural information and in the hope of shedding light on the function of this hydrophobic protein. When our efforts to prepare heavy-atom derivatives failed, we explored alternatives to isomorphous replacement for phase determination. Our experience HHS Public Access Author Manuscript Author ManuscriptAuthor ManuscriptAuthor Manuscript in using anomalous scattering to locate the iron atoms in myohaemerythrin 19 led us to contemplate an attempt based on the six sulphur atoms in crambin. An estimate of the magnitude of Bijvoet differences to be expected from crambin gave a value about half that found with myohaemerythrin and showed that sulphur scattering would account for 98% of the expected anomalous signal. The expected contribution of the sulphur partial structure to the protein diffraction pattern proved to be 29% (〈|F ...

show abstract

“…SSRL has a long history of excellence in structural biology research, including some of the first reports of X-ray absorption spectra from a biological sample (Kincaid et al, 1975), the first published report of single-crystal diffraction from protein crystals using synchrotron radiation (Phillips et al, 1976), fundamental studies of what would become the multiplewavelength anomalous diffraction phasing experiment (Phillips et al, 1977(Phillips et al, , 1978Templeton et al, 1980) and the development of insertion devices as sources of high-intensity radiation (Doniach et al, 1997).…”

Section: Synchrotron Radiation Research At Ssrlmentioning

confidence: 99%

Remote access to crystallography beamlines at SSRL: novel tools for training, education and collaboration

et al. 2010

View full text Add to dashboard Cite

For the past five years, the Structural Molecular Biology group at the Stanford Synchrotron Radiation Lightsource (SSRL) has provided general users of the facility with fully remote access to the macromolecular crystallography beamlines. This was made possible by implementing fully automated beamlines with a flexible control system and an intuitive user interface, and by the development of the robust and efficient Stanford automated mounting robotic sample-changing system. The ability to control a synchrotron beamline remotely from the comfort of the home laboratory has set a new paradigm for the collection of high-quality X-ray diffraction data and has fostered new collaborative research, whereby a number of remote users from different institutions can be connected at the same time to the SSRL beamlines. The use of remote access has revolutionized the way in which scientists interact with synchrotron beamlines and collect diffraction data, and has also triggered a shift in the way crystallography students are introduced to synchrotron data collection and trained in the best methods for collecting high-quality data. SSRL provides expert crystallographic and engineering staff, state-of-the-art crystallography beamlines, and a number of accessible tools to facilitate data collection and in-house remote training, and encourages the use of these facilities for education, training, outreach and collaborative research.

show abstract

Anomalous scattering of X-rays by cesium and cobalt measured with synchrotron radiation

Cited by 103 publications

References 10 publications

The polarization factor for a repeatedly reflected X-ray beam: special cases

The polarization factor for a repeatedly reflected X-ray beam: special cases

Structure of the hydrophobic protein crambin determined directly from the anomalous scattering of sulphur

Remote access to crystallography beamlines at SSRL: novel tools for training, education and collaboration

Contact Info

Product

Resources

About