George M. Sheldrick

Bio: George M. Sheldrick is an academic researcher from University of Göttingen. The author has contributed to research in topics: Crystal structure & Bond length. The author has an hindex of 58, co-authored 791 publications receiving 151229 citations. Previous affiliations of George M. Sheldrick include University of Regensburg.

In-house measurement of the sulfur anomalous signal and its use for phasing.

Abstract: Five test structures (orthorhombic and trigonal trypsin, cubic and rhombohedral insulin and thaumatin) have been solved by the SAD (single-wavelength anomalous diffraction) method using highly redundant data collected at 100 K with a CCD detector, rotating-anode generator and three-circle goniometer. The very weak anomalous scattering (primarily from sulfur) was sufficient to locate all the anomalous scatterers using the integrated direct and Patterson methods in SHELXD. These positions and occupancies were used without further refinement to estimate phases that were extended to native (in-house) resolution by the sphere of influence algorithm in SHELXE. The final map correlation coefficients relative to the anisotropically refined structures were in the range 0.81-0.97. The use of highly redundant medium-resolution laboratory data for sulfur-SAD phasing combined with high-resolution synchrotron native data for phase expansion and structure refinement clearly has considerable potential.

The bi-loop, a new general four-stranded DNA motif

Abstract: The crystal structure of the cyclic octanucleotide d contains two independent molecules that form a novel quadruplex by means of intermolecular Watson–Crick A⋅T pairs and base stacking. A virtually identical quadruplex composed of G⋅C pairs was found by earlier x-ray analysis of the linear heptamer d(GCATGCT), when the DNA was looped in the crystal. The close correspondence between these two structures of markedly dissimilar oligonucleotides suggests that they are both examples of a previously unrecognized motif. Their nucleotide sequences have little in common except for two separated 5′-purine-pyrimidine dinucleotides forming the quadruplex, and by implication these so-called “bi-loops” could occur widely in natural DNA. Such structures provide a mechanism for noncovalent linking of polynucleotides in vivo. Their capacity to associate by base stacking, demonstrated in the crystal structure of d(GCATGCT), creates a compact molecular framework made up of four DNA chains within which strand exchange could take place.

Die Pyridinaddukte der Goldhalogenide. 3. Darstellung, Eigenschaften und Kristallstruktur zweier Modifikationen von AuBr · NC5H5

Abstract: Bei der Umsetzung von AuBr · S(CH2C6H5)2 mit Pyridin in absolutem Ethanol kristallisiert AuBr · Pyridin in Form trikliner Kristalle mit der Raumgruppe P1 und den Gitterkonstanten a = 791,5(2) pm, b = 935,6(2) pm, c = 1005,1(3) pm, α = 85,78(2)°, β = 102,07(2)°, γ = 109,31(2)°. Wird die Reaktion dagegen in absolutem Toluol durchgefuhrt, so erhalt man eine monokline Modifikation mit der Raumgruppe C2/c und a = 1225,9(2) pm, b = 1522,2(3) pm, c = 1459,7(3) pm, s = 97,82(2)°. Die Strukturen beider Modifikationen bestehen aus linearen Au(py)2- und AuBr2-Gruppen, die durch schwache Gold-Gold-Wechselwirkungen zu kettenformigen Komplexen verbunden sind. Die trikline Modifikation bildet diskrete Au4-Zickzack-Ketten AuBr2—Au(py)2—Au(py)2—AuBr2. In der monoklinen Phase sind die Baugruppen in der Abfolge AuBr2—Au(py)2 zu unendlichen Ketten verknupft. Pyridine Adducts of Gold Halides. 3. Preparation, Properties, and Crystal Structure of Two Modifications of AuBr · NC5H5 The reaction of AuBr · S(CH2C6H5)2 with pyridine in absolute ethanol yields the crystalline compound AuBr · pyridine. It crystallizes in the triclinic space group P1 with the lattice constants a = 791.5(2) pm, b = 935.6(2) pm, c = 1005.1(3) pm, α = 85.78(2)°, β = 102.07(2)°, γ = 109.31(2)°. When the solvent is toluene, monoclinic crystals are formed with the space group C2/c and a = 1225.9(2) pm, b = 1522.2(3) pm, c = 1459.7(3) pm, β = 97.82(2)°. The triclinic structure is built up by Au4 zig-zag chains AuBr2—Au(py)2—Au(py)2—AuBr2, whereas the monoclinic phase contains infinite chains with the sequence AuBr2—Au(py)2. In each case the linkage is formed by weak Au—Au-interactions.

A short history of SHELX

Abstract: An account is given of the development of the SHELX system of computer programs from SHELX-76 to the present day. In addition to identifying useful innovations that have come into general use through their implementation in SHELX, a critical analysis is presented of the less-successful features, missed opportunities and desirable improvements for future releases of the software. An attempt is made to understand how a program originally designed for photographic intensity data, punched cards and computers over 10000 times slower than an average modern personal computer has managed to survive for so long. SHELXL is the most widely used program for small-molecule refinement and SHELXS and SHELXD are often employed for structure solution despite the availability of objectively superior programs. SHELXL also finds a niche for the refinement of macromolecules against high-resolution or twinned data; SHELXPRO acts as an interface for macromolecular applications. SHELXC, SHELXD and SHELXE are proving useful for the experimental phasing of macromolecules, especially because they are fast and robust and so are often employed in pipelines for high-throughput phasing. This paper could serve as a general literature citation when one or more of the open-source SHELX programs (and the Bruker AXS version SHELXTL) are employed in the course of a crystal-structure determination.

Crystal structure refinement with SHELXL

Abstract: The improvements in the crystal structure refinement program SHELXL have been closely coupled with the development and increasing importance of the CIF (Crystallographic Information Framework) format for validating and archiving crystal structures. An important simplification is that now only one file in CIF format (for convenience, referred to simply as `a CIF') containing embedded reflection data and SHELXL instructions is needed for a complete structure archive; the program SHREDCIF can be used to extract the .hkl and .ins files required for further refinement with SHELXL. Recent developments in SHELXL facilitate refinement against neutron diffraction data, the treatment of H atoms, the determination of absolute structure, the input of partial structure factors and the refinement of twinned and disordered structures. SHELXL is available free to academics for the Windows, Linux and Mac OS X operating systems, and is particularly suitable for multiple-core processors.

OLEX2: a complete structure solution, refinement and analysis program

Abstract: New software, OLEX2, has been developed for the determination, visualization and analysis of molecular crystal structures. The software has a portable mouse-driven workflow-oriented and fully comprehensive graphical user interface for structure solution, refinement and report generation, as well as novel tools for structure analysis. OLEX2 seamlessly links all aspects of the structure solution, refinement and publication process and presents them in a single workflow-driven package, with the ultimate goal of producing an application which will be useful to both chemists and crystallographers.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

PHENIX: a comprehensive Python-based system for macromolecular structure solution

Abstract: Macromolecular X-ray crystallography is routinely applied to understand biological processes at a molecular level. How­ever, significant time and effort are still required to solve and complete many of these structures because of the need for manual interpretation of complex numerical data using many software packages and the repeated use of interactive three-dimensional graphics. PHENIX has been developed to provide a comprehensive system for macromolecular crystallo­graphic structure solution with an emphasis on the automation of all procedures. This has relied on the development of algorithms that minimize or eliminate subjective input, the development of algorithms that automate procedures that are traditionally performed by hand and, finally, the development of a framework that allows a tight integration between the algorithms.