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.

Crystal and molecular structure of 17β-hydroxyandrost-4-en-3-one (testosterone)

Abstract: Anhydrous testosterone is monoclinic, space group P21, a= 14·720(3), b= 11·080(2), c= 10·868(2)A, β= 113·34(1)°, Z= 4. The structure was solved from diffractometer data by direct methods and refined to R 0·038 for 2498 observed (of a total of 2749) reflexions. The two independent molecules in the asymmetric unit have significantly different conformations. This finding is discussed in conjunction with results from studies on epitestosterone and two hydrated forms of testosterone in terms of the relationships between molecular structure and biological activity.

N,N'-Dilithiobis(alkylamino)phenylborane als Synthesebausteine für viergliedrige Metallacyclen

Abstract: N,N′-Dilithiobis(alkylamino)phenylboranes as Starting Materials for Four-Membered Metallacycles Reactions of N,N′-Dilithiobis(alkylamino)phenylboranes with tetrachlorides MCl4 (M = Ge, Sn, Ti, Zr) produce the 4,4′-spirobi(1,3-dialkyl-2-phenyl-1,3-diaza-2-bora-4-metalla-cyclobutane) derivatives 1a, 1b, 2b, 3a, and 3b. With diorganylmetal dihalides R2MX2(M = Sn, Zr; X = Cl, Br), the 1,3-diaza-2-bora-4-metallacyclobutanes 2a and 4 are obtained. For 3a an X-ray structure analysis has been performed.

Kristallstrukturen der selenid- bzw. sulfidverbrückten Gold(I)verbindungen [Se(AuPPh3)+3]PF6- und [S(AuPPh3)2] · CH2Cl2/Crystal Structures of the Selenide- and Sulphide-Bridged Gold(I) Complexes [Se(AuPPh3)3]+PF6- and [S(AuPPh3)2] · CH2Cl2

Abstract: Abstract The Compound [S(AUPPh3)2] · CH2Cl2 was prepared from Ph3PAuCl and H2S in CH2Cl2 and characterised by X-ray structure determination [P21/c, a = 1851.6(4), b = 2225.1(6), c = 880.3(2) pm, β = 96.32(1)°, Z = 4, R = 0.053]. A constrained refinement of the light atom positions was necessary because of pseudosymmetry. Ph3PAuPF6 reacts with Se(Sn)(CH3)3)2 to give [Se(AuPPh3)3]+PF6- which was also characterised by X-ray methods [P1̄, a = 1539.5(6), b = 1800.5(7), c = 2289.5(9) pm, α = 89.35(3), β = 72.44(3), γ = 69.75(3)°, Z = 4, R = 0.061]. There are two formula units in the asymmetric unit. Both structures show short Au···Au contacts (ca. 300-340 pm).

Structure determination of the O-methyltransferase NovP using the `free lunch algorithm' as implemented in SHELXE

Abstract: NovP is an S-adenosyl-l-methionine-dependent O-methyltransferase from Streptomyces spheroides (subunit MW = 29 967 Da). Recombinant N-terminally His-tagged NovP crystallizes in space group P2, with approximate unit-cell parameters a = 51.81, b = 46.04, c = 61.22 A, β = 105.0°, giving a solvent content of 44% for a single copy of the His-tagged protomer per asymmetric unit. Native synchrotron data to a resolution of 1.35 A were combined with three other native data sets collected at lower resolution (both in-house and at the synchrotron) for the sake of completeness and better scaling. Data to 2.45 A resolution were subsequently recorded in-house from a single mercury derivative. Three partial mercury sites could be located with SHELXD, but the resulting phases had a mean error of about 81° and in our hands did not yield an interpretable map using standard automated software. Nevertheless, the structure of NovP could be solved by first tracing a small part of the structure by hand and then extrapolating within and beyond the experimental resolution limit using the `free lunch algorithm' in SHELXE. The resulting phases have a mean phase error of 17° relative to a refined model.

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.