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Dispersion Experiment (dispersion + experiment)

Distribution by Scientific Domains
Chemistry62%

Kinds of Dispersion Experiment

  • anomalous dispersion experiment
    		•

    Selected Abstracts

    Crystallization and preliminary X-ray diffraction analysis of the N-terminal domain of Mrs2, a magnesium ion transporter from yeast inner mitochondrial membrane

    ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2010
    Muhammad Bashir Khan
    Mrs2 transporters are distantly related to the major bacterial Mg2+ transporter CorA and to Alr1, which is found in the plasma membranes of lower eukaryotes. Common features of all Mrs2 proteins are the presence of an N-terminal soluble domain followed by two adjacent transmembrane helices (TM1 and TM2) near the C-terminus and of the highly conserved F/Y-G-M-N sequence motif at the end of TM1. The inner mitochondrial domain of the Mrs2 from Saccharomyces cerevisae was overexpressed, purified and crystallized in two different crystal forms corresponding to an orthorhombic and a hexagonal space group. The crystals diffracted X-rays to 1.83 and 4.16,Å resolution, respectively. Matthews volume calculations suggested the presence of one molecule per asymmetric unit in the orthorhombic crystal form and of five or six molecules per asymmetric unit in the hexagonal crystal form. The phase problem was solved for the orthorhombic form by a single-wavelength anomalous dispersion experiment exploiting the sulfur anomalous signal. [source]

    Cloning, expression, purification, crystallization and preliminary crystallographic studies of UgdG, an UDP-glucose dehydrogenase from Sphingomonas elodea ATCC 31461

    ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 1 2010
    Joana Rocha
    Gellan gum, a commercial gelling agent produced by Sphingomonas elodea ATCC 31461, is a high-value microbial exopolysaccharide. UDP-glucose dehydrogenase (UGD; EC 1.1.1.22) is responsible for the NAD-dependent twofold oxidation of UDP-glucose to UDP-glucuronic acid, one of the key components for gellan biosynthesis. S. elodea ATCC 31461 UGD, termed UgdG, was cloned, expressed, purified and crystallized in native and SeMet-derivatized forms in hexagonal and tetragonal space groups, respectively; the crystals diffracted X-rays to 2.40 and 3.40,Å resolution, respectively. Experimental phases were obtained for the tetragonal SeMet-derivatized crystal form by a single-wavelength anomalous dispersion experiment. This structure was successfully used as a molecular-replacement probe for the hexagonal crystal form of the native protein. [source]

    Expression, purification, crystallization and preliminary X-ray crystallographic analysis of a resuscitation-promoting factor from Mycobacterium tuberculosis

    ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2007
    Alessia Ruggiero
    The resuscitation-promoting factor RpfB, the most complex of the five resuscitation-promoting factors produced by M. tuberculosis, is devoted to bacterial reactivation from the dormant state. RpfB consists of 362 residues predicted to form five domains. An RpfB fragment containing the protein catalytic domain and a G5 domain has been successfully crystallized using vapour-diffusion methods. This is the first crystallographic study of a resuscitation-promoting factor. Crystals of this protein belong to space group I422, with unit-cell parameters a = 97.63, b = 97.63, c = 114.87,Å. Diffraction data have also been collected from a selenomethionine derivative at 2.9,Å resolution. Model building using the phases derived from the multiwavelength anomalous dispersion experiment is in progress. [source]

    Microsecond Protein Dynamics Measured by 13C, Rotating-Frame Spin Relaxation

    CHEMBIOCHEM, Issue 9 2005
    Patrik Lundström
    Abstract NMR spin relaxation in the rotating frame (R1,) is a unique method for atomic-resolution characterization of conformational (chemical) exchange processes occurring on the microsecond timescale. We present a rotating-frame13C,relaxation dispersion experiment for measuring conformational dynamics in uniformly13C-labeled proteins. The experiment was validated by using the E140Q mutant of the C-terminal fragment of calmodulin, which exhibits significant conformational exchange between two major conformations, as gauged from previous15N and1H relaxation studies. Consistent with previous work, the present13C, R1,experiment detects conformational-exchange dynamics throughout the protein. The average correlation time of ,,ex,=25±8 ,s is in excellent agreement with those determined previously from1H and15N R1,relaxation data: ,,ex,=19±7 and 21±3 ,s, respectively. The extracted chemical-shift differences between the exchanging states reveal significant fluctuations in dihedral angles within single regions of Ramachandran ,,, space, that were not identified from the1H and15N relaxation data. The present results underscore the advantage of using several types of nuclei to probe exchange dynamics in biomolecules. [source]

    Hyperchaotic signal generation via DSP for efficient perturbations to liquid mixing

    INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 1 2009
    Zhong Zhang
    Abstract This paper presents the design, simulation, hardware implementation and an application in liquid mixing of some hyperchaotic circuits, based on the digital signal processing (DSP) technology. The hyperchaotic Chen's system is used as an example to show the system discretization and variable renormalization in the design process. Numerical simulation is given to verify the hardware signal generator. The implemented hardware of Chen's system generates outputs in good agreement with the numerical simulation. The hyperchaotic signal output from the DSP is applied to generate complex perturbations in liquid mixing experiments. Dye dispersion experiments show that the induced hyperchaotic motion effectively helps enhance the mixing homogeneity in the stirred-tank-based mixer in our laboratory. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    The interdependence of wavelength, redundancy and dose in sulfur SAD experiments

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2008
    Michele Cianci
    In the last decade, the popularity of sulfur SAD anomalous dispersion experiments has spread rapidly among synchrotron users as a quick and streamlined way of solving the phase problem in macromolecular crystallography. On beamline 10 at SRS (Daresbury Laboratory, UK), a versatile design has allowed test data sets to be collected at six wavelengths between 0.979 and 2.290,Å in order to evaluate the importance and the interdependence of experimental variables such as the Bijvoet ratio, wavelength, resolution limit, data redundancy and absorbed X-ray dose in the sample per data set. All the samples used in the experiments were high-quality hen egg-white lysozyme crystals. X-radiation damage was found to affect disulfide bridges after the crystals had been given a total dose of 0.20 × 107,Gy. However, with such a total dose, it was still possible in all cases to find a strategy to collect data sets to determine the sulfur substructure and produce good-quality phases by choosing an optimum combination of wavelength, exposure time and redundancy. A ,|,ano|/,(,ano), greater than 1.5 for all resolution shells was a necessary requirement for successful sulfur SAD substructure location. Provided this is achieved, it seems possible to find an optimum compromise between wavelength, redundancy and dose to provide phasing information. The choice of the wavelength should then follow the sample composition and the diffracting properties of the crystal. For strongly diffracting crystals, wavelengths equal or shorter than 1.540,Å can be selected to capture the available data (provided the Bijvoet ratio is reasonable), while a longer wavelength, to gain as high a Bijvoet ratio as possible, must be used for more weakly diffracting crystals. These results suggest that an approach to a sulfur SAD experiment based on a complete description of the crystal system and the instrument for data collection is useful. [source]

    Short-range urban dispersion experiments using fixed and moving sources

    ATMOSPHERIC SCIENCE LETTERS, Issue 2 2009
    D. E. Shallcross
    Abstract Four perfluorocarbon tracer dispersion experiments were carried out in central London, United Kingdom in 2004. These experiments were supplementary to the dispersion of air pollution and penetration into the local environment (DAPPLE) campaign and consisted of ground level releases, roof level releases and mobile releases; the latter are believed to be the first such experiments to be undertaken. A detailed description of the experiments including release, sampling, analysis and wind observations is given. The characteristics of dispersion from the fixed and mobile sources are discussed and contrasted, in particular, the decay in concentration levels away from the source location and the additional variability that results from the non-uniformity of vehicle speed. Copyright © 2009 Royal Meteorological Society [source]