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Ultrahigh Resolution (ultrahigh + resolution)
Selected AbstractsUltrahigh-resolution crystallography and related electron density and electrostatic properties in proteinsJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2008Claude Lecomte With an increasing number of biological macromolecular crystal structures measured at ultrahigh resolution (1,Å or better), it is necessary to extend to large systems the experimental valence electron density modelling that is applied to small molecules. A database of average multipole populations has been built, describing the electron density of chemical groups in all 20 amino acids found in proteins. It allows calculation of atomic aspherical scattering factors, which are the starting point for refinement of the protein electron density, using the MoPro software. It is shown that the use of non-spherical scattering factors has a major impact on crystallographic statistics and results in a more accurate crystal structure, notably in terms of thermal displacement parameters and bond distances involving H atoms. It is also possible to obtain a realistic valence electron density model, which is used in the calculation of the electrostatic potential and energetic properties of proteins. [source] Mass spectrometry of the photolysis of sulfonylurea herbicides in prairie watersMASS SPECTROMETRY REVIEWS, Issue 4 2010John V. Headley Abstract This review of mass spectrometry of sulfonylurea herbicides includes a focus on studies relevant to Canadian Prairie waters. Emphasis is given to data gaps in the literature for the rates of photolysis of selected sulfonylurea herbicides in different water matrices. Specifically, results are evaluated for positive ion electrospray tandem mass spectrometry with liquid chromatography separation for the study of the photolysis of chlorsulfuron, tribenuron-methyl, thifensulfuron-methyl, metsulfuron-methyl, and ethametsulfuron-methyl. LC,MS/MS is shown to be the method of choice for the quantification of sulfonylurea herbicides with instrumental detection limits ranging from 1.3 to 7.2,pg (on-column). Tandem mass spectrometry coupled with the use of authentic standards likewise has proven to be well suited for the identification of transformation products. To date, however, the power of time-of-flight MS and ultrahigh resolution MS has not been exploited fully for the identification of unknown photolysis products. Dissipation of the herbicides under natural sunlight fit pseudo-first-order kinetics with half-life values ranging from 4.4 to 99 days. For simulated sunlight, radiation wavelengths shorter than 400,nm are required to induce significant photolytic reactions. The correlation between field dissipation studies and laboratory photolysis experiments suggests that photolysis is a major pathway for the dissipation of some sulfonylurea herbicides in natural Prairie waters. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:593,605, 2010 [source] Comprehensive characterization of marine dissolved organic matter by Fourier transform ion cyclotron resonance mass spectrometry with electrospray and atmospheric pressure photoionizationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2010Juliana D'Andrilli We compare the ultrahigh resolution 9.4,T Fourier transform ion cyclotron resonance (FT-ICR) mass spectra of marine dissolved organic matter (DOM) isolated from two sites in the Weddell Sea (Antarctica) obtained by complementary electrospray ionization (ESI) and atmospheric pressure photoionization (APPI). Ions produced by APPI extend to higher carbon unsaturation than those produced by ESI, indicated by higher double-bond equivalents (rings plus double bonds) minus oxygen (DBE-O) values, whereas ESI-generated ions are more oxygenated. Moreover, many sulfur-containing compounds were efficiently ionized by ESI but not detected by APPI. Because the mass spectra obtained by ESI and APPI are significantly different, both are necessary to obtain a more complete description of the molecular composition of marine DOM. Copyright © 2010 John Wiley & Sons, Ltd. [source] Hydrophobin HFBII in detail: ultrahigh-resolution structure at 0.75,ÅACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2006Markus Linder Hydrophobins are small proteins secreted by filamentous fungi that have a unique ability to spontaneously form amphiphilic layers. Hydrophobins have only recently been structurally characterized through the first crystal structure determination of a protein of this class, Trichoderma reesei hydrophobin HFBII [Hakanpää, Paananen et al. (2004), J.,Biol.,Chem.279, 534,539]. The resolution of the HFBII structure has now been extended to an ultrahigh resolution of 0.75,Å. The structure was refined conventionally and multipole refinement has been initiated. The ultrahigh-resolution structure is analyzed here in detail and comparison is made to the previous atomic resolution structure of the same protein as well as to other ultrahigh-resolution structures found in the Protein Data Bank. [source] Ultrahigh-resolution structure of high-potential iron,sulfur protein from Thermochromatium tepidumACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2002Lijun Liu Crystals of the high-potential iron,sulfur protein (HiPIP) from Thermochromatium tepidum diffract X-rays to 0.80,Å using synchrotron radiation at 100,K. The crystal structure of this HiPIP was refined at this ultrahigh resolution with anisotropic temperature factors for all atoms to conventional crystallographic R factors of 0.092 and 0.101 for Fo > 4,(Fo) and all reflections, respectively. The present structure provides a more precise picture than the previous 1.5,Å structure and allows location of the positions of most H atoms. The structure revealed a partly hydrophobic cavity near the main hydrophobic area and a much larger inter-cluster approach distance (23.454,Å, the c constant of the unit cell) in the crystal packing than other types of HiPIPs. The structural features involved in the electron-transfer reaction of HiPIP are discussed. [source] Structure of Alzheimer's disease amyloid precursor protein copper-binding domain at atomic resolutionACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2007Geoffrey Kwai-Wai Kong Amyloid precursor protein (APP) plays a central role in the pathogenesis of Alzheimer's disease, as its cleavage generates the A, peptide that is toxic to cells. APP is able to bind Cu2+ and reduce it to Cu+ through its copper-binding domain (CuBD). The interaction between Cu2+ and APP leads to a decrease in A, production and to alleviation of the symptoms of the disease in mouse models. Structural studies of CuBD have been undertaken in order to better understand the mechanism behind the process. Here, the crystal structure of CuBD in the metal-free form determined to ultrahigh resolution (0.85,Å) is reported. The structure shows that the copper-binding residues of CuBD are rather rigid but that Met170, which is thought to be the electron source for Cu2+ reduction, adopts two different side-chain conformations. These observations shed light on the copper-binding and redox mechanisms of CuBD. The structure of CuBD at atomic resolution provides an accurate framework for structure-based design of molecules that will deplete A, production. [source] | ||||||||||