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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis, characterization, and molecular structures of supermesitylgallium- and supermesitylindium dihalides (1993)
    s.l. : American Chemical Society
    Inorganic chemistry 32 (1993), S. 3343-3346 
    Details
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ic00067a026
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  • 2
    Electronic Resource
    Electronic Resource
    Ab initio structure determination of the lantibiotic mersacidin (2000)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 56 (2000), S. 705-713 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structure of mersacidin, a potential novel antibiotic against methicillin- and vancomycin-resistant Staphylococcus aureus strains, has been determined by ab initio methods. Despite all crystals being merohedrally twinned, an accurate structural model with an R value of 13.4% has been obtained at atomic resolution. With six molecules in the asymmetric unit and no atom heavier than sulfur, the structure corresponds to a protein of 120 amino acids and is the largest approximately equal-atom unknown structure solved by direct methods. In the crystal, the molecule assumes a compact fold different from that found by NMR in solution. Comparison of the NCS-related molecules reveals regions of variable flexibility. The region highly homologous to the related antibiotic actagardine is very rigid and possibly defines an essential building block of this class of new antibacterial substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444900003711
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  • 3
    Electronic Resource
    Electronic Resource
    Structures of three diphtheria toxin repressor (DtxR) variants with decreased repressor activity (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 619-627 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The diphtheria toxin repressor (DtxR) from Corynebacterium diphtheriae regulates the expression of the gene on corynebacteriophages that encodes diphtheria toxin (DT). Other genes regulated by DtxR include those that encode proteins involved in siderophore-mediated iron uptake. DtxR requires activation by divalent metals and holo-DtxR is a dimeric regulator with two distinct metal-binding sites per three-domain monomer. At site 1, three side chains and a sulfate or phosphate anion are involved in metal coordination. In the DtxR–DNA complex this anion is replaced by the side chain of Glu170 provided by the third domain of the repressor. At site 2 the metal ion is coordinated exclusively by constituents of the polypeptide chain. In this paper, five crystal structures of three DtxR variants focusing on residues Glu20, Arg80 and Cys102 are reported. The resolution of these structures ranges from 2.3 to 2.8 Å. The side chain of Glu20 provided by the DNA-binding domain forms a salt bridge to Arg80, which in turn interacts with the anion. Replacing either of the salt-bridge partners with an alanine reduces repressor activity substantially and it has been inferred that the salt bridge could possibly control the wedge angle between the DNA-binding domain and the dimerization domain, thereby modulating repressor activity. Cys102 is a key residue of metal site 2 and its substitution into a serine abolishes repressor activity. The crystal structures of Zn-Glu20Ala-DtxR, Zn-Arg80Ala-DtxR, Cd-Cys102Ser-DtxR and apo-Cys102Ser-DtxR in two related space groups reveal that none of these substitutions leads to dramatic rearrangements of the DtxR fold. However, the five crystal structures presented here show significant local changes and a considerable degree of flexibility of the DNA-binding domain with respect to the dimerization domain. Furthermore, all five structures deviate significantly from the structure in the DtxR–DNA complex with respect to overall domain orientation. These results confirm the importance of the hinge motion for repressor activity. Since the third domain has often been invisible in previous crystal structures of DtxR, it is also noteworthy that the SH3-like domain could be traced in four of the five crystal structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090744490100230X
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  • 4
    Electronic Resource
    Electronic Resource
    1.7 Å structure of the stabilized REIv mutant T39K. Application of local NCS restraints (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 1158-1167 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The X-ray structure of the T39K mutant of the variable domain of a human immunoglobulin κ light chain has been determined at room temperature to 1.7 Å resolution with a conventional R factor of 0.182. T39K crystallizes in the triclinic space group P1 [a = 35.4 (1), b = 40.1 (1), c = 43.1 (1) Å, α = 66.9 (1), β = 85.4 (1), γ = 73.8 (1)°]. The unit-cell contains two monomers, related by a non-crystallographic twofold axis. The use of a novel type of local non-crystallographic symmetry restraints on related isotropic displacement parameters and 1–4 distances as incorporated in the refinement program SHELXL improves the model and quality of the maps, but local differences between both monomers in areas subject to different packing contacts can still be observed. 12 overall anisotropic scaling parameters were refined. These may have compensated for the difficulties in accurately scaling single rotation axis image-plate data from a triclinic crystal, because of the scarcity of common equivalent reflections. The final model has been used to perform a number of tests on anisotropic scaling, non-crystallographic symmetry, anisotropic refinement, determination of standard uncertainties and bulk solvent correction. It is remarkable that removal of the NCS restraints from the final model caused Rfree to increase. These tests clarify the strategies for optimum use of SHELXL for refinement at medium as opposed to atomic resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444999003972
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  • 5
    Electronic Resource
    Electronic Resource
    Crystallization of redox-insensitive Oct1 POU domain with different DNA-response elements (2001)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 57 (2001), S. 1634-1638 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The POU domain of the human Oct1 transcription factor has been crystallized with two different POU-dimer-binding DNA elements. Protein–DNA cocrystals suitable for structural analysis could be obtained only with a redox-insensitive version of the POU domain. The recombinant protein expression in a prokaryotic host was adjusted for fast purification. Optimized crystals were obtained by systematically varying the length of the oligonucleotide and by modifying cryofreezing procedures. These steps are generally applicable to the preparation of protein–DNA complexes for structural studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S090744490101099X
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  • 6
    Electronic Resource
    Electronic Resource
    A new, simple access to pentacarbonyl(3-aminoallenylidene)chromium complexes (1993)
    s.l. : American Chemical Society
    Organometallics 12 (1993), S. 2556-2564 
    Details
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/om00031a028
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  • 7
    Electronic Resource
    Electronic Resource
    Architecture of a protein central to iron homeostasis: crystal structure and spectroscopic analysis of the ferric uptake regulator (2003)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 47 (2003), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Iron is an essential element for almost all organisms, although an overload of this element results in toxicity because of the formation of hydroxyl radicals. Consequently, most living entities have developed sophisticated mechanisms to control their intracellular iron concentration. In many bacteria, including the opportunistic pathogen Pseudomonas aeruginosa, this task is performed by the ferric uptake regulator (Fur). Fur controls a wide variety of basic physiological processes including iron uptake systems and the expression of exotoxin A. Here, we present the first crystal structure of Fur from P. aeruginosa in complex with Zn2+ determined at a resolution of 1.8 Å. Furthermore, X-ray absorption spectroscopic measurements and microPIXE analysis were performed in order to characterize the distinct zinc and iron binding sites in solution. The combination of these complementary techniques enables us to present a model for the activation and DNA binding of the Fur protein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03337.x
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  • 8
    Electronic Resource
    Electronic Resource
    Overview of the tunable beamlines for protein crystallography at the EMBL Hamburg Outstation; an analysis of current and future usage and developments (2001)
    Chester : International Union of Crystallography (IUCr)
    Journal of synchrotron radiation 8 (2001), S. 1113-1120 
    Details
    ISSN: 1600-5775
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: The EMBL Hamburg Outstation currently operates two tunable protein crystallography beamlines suitable for single and multiple anomalous diffraction (SAD/MAD) experiments. The first beamline, designated X31, is located on a bending magnet of the DORIS III storage ring whereas the second beamline, BW7A, is positioned at a multipole wiggler at the same storage ring. X31 is equipped with an energy stabilization device to ensure constant wavelength during longer data-collection periods. The in-house built crystallographic end-station is now equipped with a Mar345 imaging-plate scanner as a detector. The wiggler beamline BW7A features a novel sagitally focusing monochromator. The end-station used here has also been developed and built in-house. The beamline is currently operated with a Mar165 CCD detector. In this paper the hardware and software developments of the last years will be summarized and the outlook for substantial upgrades will be given. The future plans include the design and construction of a third tunable beamline, designated X12, for protein crystallography. The development of automated beamlines in protein crystallography is of particular importance with respect to structural genomics initiatives. The analysis of the projects of the last years shows the wide range of anomalous scatterer used on the tunable beamlines thus demonstrating the need of a wide range of accessible energies and fast and reliable energy changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0909049501005891
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  • 9
    Electronic Resource
    Electronic Resource
    Absolute configurations of Emycin D, E and F; mimicry of centrosymmetric space groups by mixtures of chiral stereoisomers (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 607-616 
    Details
    ISSN: 1600-5740
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The crystal structures of Emycin E (1), di-o-bromobenzoyl-Emycin F (2) and o-bromobenzoyl-Emycin D (3) have been determined by X-ray analysis at low temperature. Emycin E and o-bromobenzoyl-Emycin D both crystallize with two molecules in a triclinic unit cell. These two structures can be solved and refined either in the centrosymmetric space group P1¯, with apparent disorder localized at or around the expected chiral centre, or in the non-centrosymmetric space group P1 as mixtures of two diastereomers without disorder. Only the latter interpretation is consistent with the chemical and spectroscopic evidence. Refinements in the centrosymmetric and non-centrosymmetric space groups are compared in this paper and are shown to favour the chemically correct interpretation, more decisively so in the case of the bromo derivative as a result of the anomalous dispersion of bromine. Structures (1) and (3) provide a dramatic warning of the dangers inherent in the conventional wisdom that if a structure can be refined satisfactorarily in both centrosymmetric and non-centrosymmetric space groups, the former should always be chosen. In these two cases, despite apparently acceptable intensity statistics and R factors (5.87 and 3.55%), the choice of the centrosymmetric space group leads to the serious chemical error that the triclinic unit cell contains a racemate rather than two chiral diastereomers! The weakest reflections are shown to be most sensitive to the correct choice of space group, underlining the importance of refining against all data rather than against intensities greater than a specified threshold. The use of similar-distance restraints is shown to be beneficial in both P1 refinements. Di-o-bromobenzoyl-Emycin F crystallizes in the monoclinic space group P21 with one molecule in the asymmetric unit and so does not give rise to these problems of interpretation. The absolute configuration of the two bromo derivatives, and hence the Emycins in general, was determined unambiguously as S at the chiral centre C3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108768199003948
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  • 10
    Electronic Resource
    Electronic Resource
    The Molecular and Crystal Structure of the Glycopeptide A-40926 Aglycone (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 1916-1924 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of a glycopeptide antibiotic A-40926 aglycone was investigated by X-ray analysis at -120°. A-40926 crystallises in the orthorhombic space group P212121 with two monomers in the asymmetric unit, a = 21.774(4), b = 28.603(7), c = 29.757(4) Å. ‘Conventional’ direct methods approach failed to solve the structure, but a novel iterative real/reciprocal space procedure was successful. Refinement against 11248 F2 data led to R1 = 13.3% for 6770 F 〉 4σ (F). The two monomers of A-40926 have similar conformations and are bound by antiparallel H-bonds to form a ‘chain’ structure of connecting dimers. The antibiotic molecule possesses a ‘binding pocket’ for the C-terminal carboxy group of the cell-wall protein, which is consisten with suggestions based on NMR data and the recently reported crystal structure of ureido-balhimycin. In A-40926 the monomers are polymerically linked by H-bonds, quite unlike the tight dimer formation observed in ureido-balhimycin.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790714
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