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At least 19 recordsLinked to original sources
PubMed2005

New synchrotron radiation circular dichroism end-station on DISCO beamline at SOLEIL synchrotron for biomolecular analysis.

The novel Synchrotron Radiation Circular Dichroism (SRCD) technique is becoming a new tool of investigation for the molecular structures of biomolecules, like proteins, carbohydrates or others bio-materials. Here, we describe the characteristics of a new experimental end-station for circular dichroism studies, in construction on DISCO beamline at SOLEIL synchrotron (Saint-Aubin, France). This experimental end-station will be an open facility for the community of researchers in structural biology. In order to show the kind of information accessible with this type of technique, we give an example: the conformational study of the galactose mutarotase from Escherichia coli, an enzyme involved in the galactose metabolism. This study was made using an operational SRCD station available at SRS (Daresbury Laboratory, UK).

Amino Acid Sequence↗
PubMed2007

Synchrotron radiation-based irradiance calibration from 200 to 400 nm at the Synchrotron Ultraviolet Radiation Facility III.

A new facility for measuring irradiance in the UV was commissioned recently at the National Institute of Standards and Technology (NIST). The facility uses the calculable radiation from the Synchrotron Ultraviolet Radiation Facility as the primary standard. To measure the irradiance from a source under test, an integrating sphere spectrometer-detector system measures both the source under test and the synchrotron radiation sequentially, and the irradiance from the source under test can be determined. In particular, we discuss the calibration of deuterium lamps using this facility from 200 to 400 nm. This facility improves the current NIST UV irradiance scale to a relative measurement uncertainty of 1.2% (k=2).

Journal Article↗
PubMed2004

Synchrotron radiation in radiology: radiology techniques based on synchrotron sources.

The characteristics of synchrotron X-ray sources--quite different from those of conventional sources--are exploited by several new imaging techniques. These techniques expand the capabilities of conventional radiology and find interesting application in special cases. We briefly review the basic principle, applications and limitations of the most important of them: monochromatic mammography, two-wavelength digital subtraction angiography, phase-contrast/edge-enhancement imaging, diffraction-enhanced imaging and microtomography.

Angiography↗
PubMed2005

Synchrotron and simulations techniques applied to problems in materials science: catalysts and Azul Maya pigments.

Development of synchrotron techniques for the determination of the structure of disordered, amorphous and surface materials has exploded over the past 20 years owing to the increasing availability of high-flux synchrotron radiation and the continuing development of increasingly powerful synchrotron techniques. These techniques are available to materials scientists who are not necessarily synchrotron scientists through interaction with effective user communities that exist at synchrotrons such as the Stanford Synchrotron Radiation Laboratory. In this article the application of multiple synchrotron characterization techniques to two classes of materials defined as 'surface compounds' is reviewed. One class of surface compounds are materials like MoS(2-x)C(x) that are widely used petroleum catalysts, used to improve the environmental properties of transportation fuels. These compounds may be viewed as 'sulfide-supported carbides' in their catalytically active states. The second class of 'surface compounds' are the 'Maya blue' pigments that are based on technology created by the ancient Maya. These compounds are organic/inorganic 'surface complexes' consisting of the dye indigo and palygorskite, common clay. The identification of both surface compounds relies on the application of synchrotron techniques as described here.

Journal Article↗
PubMed1999

Radiobiological studies using synchrotron-produced ultrasoft X-rays.

Ultrasoft X-rays have been extensively used to explore radiobiological mechanisms surrounding cell killing. These studies for the most part have been linked to a small number of X-ray energies. Recently, this field of study has been broadened by the availability of synchrotron-produced ultrasoft X-rays which can be produced at any desired energy. We have taken advantage of the University of Wisconsin Synchrotron to reexamine two fundamental radiobiological questions: Dose RBE vary with different ultrasoft X-ray energies? Dose the fraction of the nuclear volume exposed to equal total X-ray energy modify cell cytotoxicity? The first study focuses on the survival of Chinese hamster V79 and mouse C3H10T1/2 cells irradiated with synchrotron-produced 273 eV and 860 eV ultrasoft X-rays. These two energies, which are available by multilayer monochromatization of the synchrotron output spectrum, exhibit equal attenuation within living cells. Such an isoattenuating energy pair allows the direct examination of how biological effectiveness varies with the energy of the ultrasoft X-rays. In comparing survival results, we find similar biological effectiveness of these two energies for both the C3H10T1/2 and the V79 cells. These results are no consistent with previous findings of increasing RBE with decreasing ultrasoft X-ray energies. In addition, after correcting for mean nuclear based on measurements of cell thickness obtained with confocal microscopy, we find no significant differences in survival between the two ultrasoft X-ray energies and 250 kVp X-rays. These results suggest that RBE does not increase with decreasing energy of ultrasoft X-ray between 860 eV and 273 eV. In a second study we introduced an method which allows partial-volume irradiation of live cells using synchrotron-produced ultrasoft X-rays and micro-fabricated irradiation masks. The masks were made by X-ray lithography at the University of Wisconsin Synchrotron Radiation Center, and they consist of 1.85-micron-wide stripes of gold 1.35 microns apart plated onto thin silicon nitrate membranes. When placed adjacent to mylar on which live cells are plated, these masks allow cells to be irradiated in a striped pattern with dimensions much smaller than the cell nuclei. Using 1340 eV synchrotron-produced X-rays, we compare the survival of cells subjected to uniform irradiation and cells subjected to partial-volume irradiation. Our results show that, at equal mean dose to the nucleus (i.e. equal total energies deposited), survival is not statistically different for the two treatments over a wide range of doses. Thus, imparting equal energies to smaller intranuclear volumes does not appear to modulate cell killing.

Animals↗
PubMed2005

Beam dumps design and local radiation protection at TERA synchrotron.

The realisation of the National Center of Hadrontherapy was funded by the Italian Government in 2002. The Centre will be built in the area of Pavia (Italy). The synchrotron designed in the framework of this programme will accelerate protons and carbon ions up to 250 MeV and 400 MeV u(-1), respectively. Some of the main aspects which were taken into account in the design of the acceleration system are the patient's safety and the beam control. From this point of view an important role is played by the beam dumps in the synchrotron ring and upstream of the extraction system. In particular, an horizontal and a vertical beam dump will be installed in the synchrotron ring: the former will be used for lowering the beam intensity and the latter for beam abortion. The dump at the extraction will absorb the particles during the mounting and the falling ramps of the synchrotron magnetic cycle, thus extracting only the flat top of the ion spill. Beam dumps can produce intense fields of secondary radiation (neutrons, charged light-hadrons and photons) and high rates of induced activity, since they can absorb the beam completely. Usually they have to be shielded to protect the electronics during machine operation and to attenuate the radiation dose below the limits imposed by the law when the personnel access to the synchrotron hall. The part of the shielding design of the beam dumps concerning with the acceleration of protons was made using Monte Carlo simulations with the FLUKA code. Both induced activity and secondary radiation were taken into account. The shields against secondary radiation produced by carbon ions were designed, referring only to secondary neutrons, taking double-differential distributions from the literature as sources for the FLUKA simulations. The induced activity from carbon ions interactions was estimated analytically, using the data generated by the EPAX 2 code. The dose-equivalent rates from the induced radionuclides were calculated at 1 m from the shielded dumps, taking into account the contribution of activated components of the synchrotron ring.

Computer Simulation↗
PubMed1999

Accurate charge densities in days - use of synchrotrons, image plates and very low temperatures.

Extensive synchrotron (28 K) and conventional sealed-tube (9 K) X-ray diffraction data have been collected on tetrakis(dimethylphosphinodithioato-S,S')thorium(IV), [Th(S(2)PMe(2))(4)]. The use of very low temperatures, well below those obtained with liquid-nitrogen cooling, is crucial for the accuracy of the data. This is due to minimization of temperature-dependent systematic errors such as TDS and anharmonicity, and extension and intensification of the data in reciprocal space. Comparison of structural parameters derived separately from the sealed-tube data and the synchrotron data shows good agreement. The synchrotron data are markedly superior when comparing refinement residuals, standard uncertainties (s.u.'s) of the data and s.u.'s of the derived parameters. However, the study suggests that there are still small uncorrected systematic errors in the data. The very large extent [(sinstraight theta/lambda)(max) = 1.77 Å(-1)] of the synchrotron data and the very low temperature at which they were collected makes it possible to separate anharmonic effects from electron-deformation effects even with only an X-ray data set at a single temperature. The electron density shows a large polarization of the outer Th core of d-type symmetry. This deformation is successfully modelled with contracted multipolar functions, which are only slightly correlated with anharmonic expansions in reciprocal space when using the full extent of the data. In the data collection more than a factor of 100 in speed is gained by use of image-plate area detectors at the synchrotron source compared with conventional sequential measurements. Thus accurate, very low temperature synchrotron-radiation diffraction data can now be measured within days, which makes electron-density studies of compounds beyond the first transition series more frequently within reach.

Journal Article↗
PubMed1997

Development of a tunable UV laser system synchronizing precisely with synchrotron radiation pulses from UVSOR.

A mode-locked Ti:sapphire laser is made to oscillate at the frequency of the UVSOR storage ring, 90.115 MHz, in a multi-bunch operation mode. The third harmonic of the laser is available in the wavelength range 243-280 nm. Synchrotron radiation from an undulator is monochromated by a grazing-incidence monochromator and introduced coaxially with the laser. The temporal profile of the photon pulses is monitored in situ by a luminescing substance/photomultiplier combination. The delay timing between the laser and synchrotron radiation can be changed from 0 to 11 ns by adjusting an electronic module that provides phase-locked loop stabilization of the laser pulse. The reliability and feasibility of this laser-synchrotron radiation combination technique are demonstrated by applying pump-probe experiments to two physical systems. The first system is photodissociation of iodomethane (CHA) with a laser photon, followed by photoionization of I and CH3 fragments with synchrotron radiation. The second, two-photon ionization of He atoms, is studied as the prototype of a time-resolved experiment. The He+ signal counts as a function of the laser-synchrotron radiation delay are found to be enhanced in a narrow time window, which can be interpreted in terms of a short lifetime of the resonant state, He*(1s2p 1P), produced by primary synchrotron radiation excitation.

Journal Article↗
PubMedDate not supplied

Angle-dispersive diffraction with synchrotron radiation at Laboratório Nacional de Luz Síncrotron (Brazil): potential for use in biomedical imaging.

At low angles the scattering of X-rays in the diagnostic energy range (low-momentum transfer), it is probable that the scattering interaction will be coherent. This coherence gives rise to interference effects resulting in X-ray diffraction patterns that are characteristic of the scattering material. The usefulness of coherent scattering is not limited to crystallography. It can provide information about biological material as well. The interatomic and intermolecular co-operative effects which modify the free-atom coherent scattering process are well known for highly ordered structures such as crystalline materials but are important for amorphous solids and liquids where short-range ordering occurs. X-ray diffraction using synchrotron radiation has became a well established technique. This work introduces a non-destructive synchrotron radiation X-ray diffraction imaging technique. The feasibility of the X-ray diffraction computed microtomography using synchrotron radiation has been investigated. This research was carried out at the X-ray diffraction beam line of the National Synchrotron Light Laboratory supported by the National Council for Scientific and Technological Development (LNLS/CNPq) in Brazil. These experimental patterns were carried out with a 500 microm slit in front of the detector and an 11.101 keV beam (lambda = 1.117 A) monochromatic beam from the double crystal monochromator. The diffracted beam was detected by a fast scintillation detector (10(6) counts s(-1)) designed specifically to meet the needs of high quality X-ray diffraction and synchrotron radiation experiments. The data were recorded at rates of one second per degree of 2theta (angular steps equal to 0.05 +/- 0.01 degrees) and registered by a multichannel analyzer. These experimental data could be used to evaluate the scattering properties of different tissue-substitute (water, lucite, nylon, plastic and polystyrene) and bone-substitute (hydroxyapatite and aluminum) materials. The data are in good agreement with those obtained by other authors, indicating the feasibility of the imaging technique.

Aluminum↗
PubMed1997

Medical applications of synchrotron radiation x-rays.

The use of synchrotron radiation is not widespread in the field of medicine and in fact few health-care professionals have even heard of it. It is the purpose of this article to explain what it is and to give some examples of how it can contribute to medical science. X-rays have been used for diagnostic medical imaging for more than 100 years and, whilst new techniques such as computed tomography have been developed, the means of producing x-rays has altered little during that time. Synchrotron radiation sources provide multiple, extremely intense and tuneable beams of photons over a huge range of energies from infrared through to hard x-rays. Their advent has revolutionized many experimental techniques and synchrotron radiation is being applied across many fields from imaging to molecular dynamics. It has spawned several methods for studying live and wet tissue samples, yielding information on both structure and composition on all length scales down to atomic resolution. Such techniques have played a crucial role in the development of molecular biology and the solution of protein structures. The application of synchrotron radiation in the field of radiography is now expanding and it is clear that very substantial improvements in image quality and patient dose can be realized. Following an overview of the production and properties of synchrotron radiation, some of the ways in which this remarkable tool has already been exploited for medical research are reviewed and some potential clinical opportunities highlighted.

Animals↗
PubMed2004

High-resolution synchrotron data collection for charge-density work at 100 and 20 K.

For the measurement of very accurate high-resolution X-ray data for charge-density work, synchrotron beamlines provide a bright radiation source of outstanding properties. Most important are the very high primary intensity and the possibility of choosing hard radiation with lambda approximately 0.5 A or even shorter. This together with area detection and a stable low-temperature device means that accurate and large data sets can be measured in a short time. A number of data collections are reported, which were carried out at the beamlines F1 and D3 of Hasylab (DESY, Hamburg) first at 100 K and later at 15-20 K, demonstrating the quality of the measured intensities. A low temperature of around 20 K was obtained at beamline D3 with a double-stage closed-cycle helium cryostat where the standard beryllium cylinder of the vacuum chamber was replaced by a 0.1 mm Kapton film. Comparison of different data sets measured for a strychnine crystal demonstrated how I/sigma ratios favorably improve if synchrotron radiation at a low temperature of 15 K was used. Synchrotron-based studies on several biologically active compounds are briefly summarized and a synchrotron experiment of an otherwise not sufficiently diffracting crystal of a tetraphenyl barbaralane derivative is described in detail. Atomic volumes and charges of a highly substituted C(60) fullerene are reported derived from a synchrotron data set of more than 350000 reflections.

Amino Acids↗
PubMed2002

Center for Synchrotron Biosciences' U2B beamline: an international resource for biological infrared spectroscopy.

A synchrotron infrared (IR) beamline, U2B, dedicated to the biomedical and biological sciences has been constructed and is in operation at the National Synchrotron Light Source (NSLS) of Brookhaven National Laboratory. The facility is operated by the Center for Synchrotron Biosciences of the Albert Einstein College of Medicine in cooperation with the NSLS. Owing to the broadband nature of the synchrotron beam with brightness 1000 times that of conventional sources, Fourier transform IR spectroscopy experiments are feasible on diffraction-limited sample areas at high signal-to-noise ratios and with relatively short data-acquisition times. A number of synchrotron IR microscopy experiments that have been performed in the mid-IR spectral range (500-5000 cm(-1)) are summarized, including time-resolved protein-folding studies in the microsecond time regime, IR imaging of neurons, bone and other biological tissues, as well as imaging of samples of interest in the chemical and environmental sciences. Owing to the high flux output of this beamline in the far-IR region (50-500 cm(-1)), investigations of hydrogen bonding and dynamic molecular motions of biomolecules have been carried out from 10 to 300 K using a custom-made cryostat and an evacuated box. This facility is intended as an international resource for biological IR spectroscopy fully available to outside users based on competitive proposal.

Bone and Bones↗
PubMed2004

Protein Data Bank depositions from synchrotron sources.

A survey and analysis of Protein Data Bank (PDB) depositions from international synchrotron radiation facilities, based on the latest released PDB entries, are reported. The results (http://asdp.bnl.gov/asda/Libraries/) show that worldwide, every year since 1999, more than 50% of the deposited X-ray structures have used synchrotron facilities, reaching 75% by 2003. In this web-based database, all PDB entries among individual synchrotron beamlines are archived, synchronized with the weekly PDB release. Statistics regarding the quality of experimental data and the refined model for all structures are presented, and these are analysed to reflect the impact of synchrotron sources. The results confirm the common impression that synchrotron sources extend the size of structures that can be solved with equivalent or better quality than home sources.

Crystallography, X-Ray↗