The 4 X 4 multiple CCD X-ray detector installed in the beamline 45XU of the SPring-8 facility in Japan was examined by acquiring X-ray diffraction images of lysozyme crystals. The detector system was calibrated at the beamline by observing X-ray images of a flood-field and a mask pattern generated by the synchrotron radiation X-ray beam. It was found in the present work that the quality of the X-ray images observed is limited by an unexpected spike noise, the origin of which was suspected to be the (gamma) -rays emitted from the radioisotopes remaining in the X-ray scintillating screen. Image analysis carried out with a median filter predicted, however, that the image quality could be as high as designed, once the noise as well as the grain colonization is removed from the screen.
Abstract The replacement of Phe120 with other hydrophobic residues causes a decrease in the activity and thermal stability in ribonuclease A (RNase A). To explain this, the crystal structures of wild‐type RNase A and three mutants—F120A, F120G, and F120W—were analyzed up to a 1.4 Å resolution. Although the overall backbone structures of all mutant samples were nearly the same as that of wild‐type RNase A, except for the C‐terminal region of F120G with a high B‐factor, two local conformational changes were observed at His119 in the mutants. First, His119 of the wild‐type and F120W RNase A adopted an A position, whereas those of F120A and F120G adopted a B position, but the static crystallographic position did not reflect either the efficiency of transphosphorylation or the hydrolysis reaction. Second, His119 imidazole rings of all mutant enzymes were deviated from that of wild‐type RNase A, and those of F120W and F120G appeared to be “inside out” compared with that of wild‐type RNase A. Only ∼1 Å change in the distance between N ε2 of His12 and N δ1 of His119 causes a drastic decrease in k cat , indicating that the active site requires the strict positioning of the catalytic residues. A good correlation between the change in total accessible surface area of the pockets on the surface of the mutant enzymes and enthalpy change in their thermal denaturation also indicates that the effects caused by the replacements are not localized but extend to remote regions of the protein molecule.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCrystal structure of l-tris(1,10-phenathroline)iron(II) bis(antimony(III) d-tartrate) octahydrateAllan Zalkin, David H. Templeton, and Tatzuo UekiCite this: Inorg. Chem. 1973, 12, 7, 1641–1646Publication Date (Print):July 1, 1973Publication History Published online1 May 2002Published inissue 1 July 1973https://pubs.acs.org/doi/10.1021/ic50125a033https://doi.org/10.1021/ic50125a033research-articleACS PublicationsRequest reuse permissionsArticle Views270Altmetric-Citations75LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts
Small-angle scattering of soft X-rays by polystyrene latex spheres was studied using the synchrotron radiation from the electron synchrotron operated at about 1 GeV at the Institute for Nuclear Study, University of Tokyo. The exposure time required to make three smallest-angle diffraction peaks visible on a photographic plate was 2 min with the soft X-rays (46.8 Å) of the synchrotron radiation, compared to 400 min with the CKα radiation (44.8 Å) from the X-ray tube operated at 3 kV ×50 mA. The diffraction patterns were so distinct that inter-particle interference functions could be derived with four diffraction peaks. Experimental results as a whole suggest that soft X-rays in the synchrotron radiation will be very useful in studying two-dimensional structures of thin organic materials with the thickness of microns or submicrons.
The surface of the epitaxial layer of AlP grown by atomic layer epitaxy (ALE) was observed by atomic force microscopy. It was discovered that the atomic scale surface flatness was not always retained during ALE growth even though the self-limiting growth of 1 monolayer per 1 alternative source gas supply was maintained. A reaction process model that focused on the methyl adsorbate lifetime on the Al surface was proposed to explain the experimental results. Based on this model, AlP surface morphology was improved by gas feeding control, and a flat surface with atomic steps was obtained even after 250 cycles of the ALE sequence.
