Michael Mark Woolfson. 9 January 1927—23 December 2019

Biographical Memoirs of Fellows of the Royal Society ◽

10.1098/rsbm.2021.0018 ◽

2021 ◽

Author(s):

Keith S. Wilson ◽

Eleanor J. Dodson

Keyword(s):

Solar System ◽

Dynamical Evolution ◽

Direct Methods ◽

Theory And Practice ◽

Phase Problem ◽

General Study ◽

X Ray ◽

X Ray Crystallography ◽

The World ◽

Young Researchers

Michael Woolfson contributed enormously to the theory and practice of X-ray crystallography for almost 60 years. He extended the theory of ‘direct methods’, which provided a general solution of the crystallographic phase problem from the measured diffraction data alone, and provided tools to exploit this theory. Software developed in his laboratory, such as the computer package MULTAN, was responsible for about half of the structures determined around the world in the 1970s and 1980s. His parallel work on the origin of the Solar System renewed interest in the Capture theory, and he contributed numerous stimulating ideas to the general study of the origin and dynamical evolution of the Solar System. Michael was a great educator and mentor for both undergraduates and young researchers, and many of these went on to make significant scientific contributions.

Download Full-text

Inorganic Crystal Structures Solved from EM Images and Refined to 0.02 À Accuracy Against Electron Diffraction Data

Microscopy and Microanalysis ◽

10.1017/s1431927600012599 ◽

1997 ◽

Vol 3 (S2) ◽

pp. 1141-1142

Author(s):

Sven Hovmöller ◽

Xiaodong Zou ◽

Thomas Weirich

Keyword(s):

Single Crystal ◽

Organic Molecules ◽

Direct Methods ◽

Electron Diffraction Data ◽

Crystal Data ◽

Phase Problem ◽

X Ray Diffraction ◽

X Ray ◽

X Ray Crystallography ◽

Inorganic Crystal

Single crystal X-ray diffraction is the traditional method for accurate crystal structure determination. A major difficulty in X-ray crystallography is the phase problem; diffracted intensities contain amplitude information but no phases. In order to solve a structure, the phases of at least the strongest reflections must be estimated by Patterson techniques, so-called direct methods or in any other way. Once the structure has been solved (i.e. the atoms found to within about 0.2 Ångström of their correct positions), then refinement is rather straight-forward for single crystal data. Typically, single crystals diffract to about 1 Â resolution. After refinement, the atomic co-ordinates are obtained with an accuracy of about 0.01 Â for organic molecules and down to 0.001 Â for inorganic structures. One limitation of single crystal X-ray diffraction is that the crystals need to be at least about 10μm in all dimensions in order to diffract, even if the radiation source is a synchrotron.

Download Full-text

Configurational and conformational studies on condensation products of biogenic amines with 2,5-anhydro-D-mannose

Canadian Journal of Chemistry ◽

10.1139/v85-483 ◽

1985 ◽

Vol 63 (11) ◽

pp. 2915-2921 ◽

Cited By ~ 7

Author(s):

Ian M. Piper ◽

David B. MacLean ◽

Romolo Faggiani ◽

Colin J. L. Lock ◽

Walter A. Szarek

Keyword(s):

Hydrogen Bond ◽

Intermolecular Hydrogen Bond ◽

Direct Methods ◽

Conformational Studies ◽

X Ray ◽

X Ray Crystallography ◽

H Nmr ◽

Twist Conformation ◽

Cell Dimensions ◽

Internal Hydrogen Bond

The products of a Pictet–Spengler condensation of tryptamine and of histamine with 2,5-anhydro-D-mannose have been studied by X-ray crystallography to establish their absolute configuration. 1(S)-(α-D-Arabinofuranosyl)-1,2,3,4-tetrahydro-β-carboline (1), C16H20N20O4, is monoclinic, P21 (No. 4), with cell dimensions a = 13.091(4), b = 5.365(1), c = 11.323(3) Å, β = 115.78(2)°, and Z = 2. 4-(α-D-Arabinofuranosyl)imidazo[4,5-c]-4,5,6,7-tetrahydropyridine (3), C11H17N3O4, is orthorhombic, P212121 (No. 19), with cell dimensions a = 8.118(2), b = 13.715(4), c = 10.963(3) Å, and Z = 4. The structures were determined by direct methods and refined to R1 = 0.0514, R2 = 0.0642 for 3210 reflections in the case of 1, and to R1 = 0.0312, R2 = 0.0335 for 1569 reflections in the case of 3. Bond lengths and angles within both molecules are normal and agree well with those observed in related structures. In 3 the base and sugar adopt a syn arrangement, which is maintained by an internal hydrogen bond between O(2′) and N(3). The sugar adopts a normal 2T3 twist conformation. The sugar has the opposite anti arrangement in the β-carboline 1 and the conformation of the sugar is unusual; it is close to an envelope conformation with O(4′) being the atom out of the plane. This conformation is caused by a strong intermolecular hydrogen bond from O(5′) in a symmetry-related molecule to O(4′). Both compounds are held together in the crystal by extensive hydrogen-bonding networks. The conformations of the compounds in solution have been investigated by 1H nmr spectroscopy, and the results obtained were compared with those obtained by X-ray crystallography for 1 and 3.

Download Full-text

Reminiscences and discoveries: Dorothy Hodgkin and the Indian connection

Notes and Records the Royal Society journal of the history of science ◽

10.1098/rsnr.1996.0010 ◽

1996 ◽

Vol 50 (1) ◽

pp. 115-127 ◽

Cited By ~ 1

Keyword(s):

Large Angle ◽

Direct Methods ◽

Statistical Fluctuation ◽

Organic Crystals ◽

X Ray Diffraction ◽

X Ray ◽

X Ray Crystallography ◽

Angle Scattering ◽

Molecular Sizes ◽

Indian Institute Of Science

Dorothy Hodgkin - as crystallographer, scientist and human being - far surpasses most, and so it is not easy to write about her many-splendoured personality. Instead, my aim here will he to discuss her influence on the growth of X-ray crystallography in India, directly through those who worked with her and indirectly by her travelling all over this country. In such an account, one must be pardoned for some personal element creeping in. In the twenties, India had developed a fairly strong tradition in X-ray physics. The six-week visit of C.V. Raman to Europe in 1921 greatly changed his research interests. On seeing the blue of the Mediterranean he started his researches on the scattering of light in liquids which finally culminated in the discovery of what is now called the Raman Effect. His encounter with Sir William Bragg and his work on naphthalene structure started three lines of research in India. First, Raman fabricated an X-ray tube and was amongst the earliest to use X-ray diffraction as a structural tool to study liquids. He showed that while in large-angle scattering the haloes reflected specific molecular sizes and packing shapes, small-angle scattering was directly related to the statistical fluctuation of density in a liquid. Second, Raman knew that Bragg’s first structure of naphthalene was not consistent with its birefringence, while the second one was. With this as cue he and his school launched extensive studies on the optical and magnetic anisotropy of organic crystals to get vital information on the arrangements of molecules in the crystalline state. Third, one of his students, Kedareshwar Bannerjee, was amongst the earliest to probe into the problem of phase determination by direct methods and for this he used Bragg’s data on naphthalene. Unfortunately, in spite of this early lead, it was not until 1951 that the first crystal structure was solved in India using Fourier methods by Gopinath Kartha. The Indian Institute of Science (IISc) had great hopes of starting a powerful school of X-ray crystallography when G.N. Ramachandran came back from Cambridge. But he went over to Madras, and there he established one of the most renowned Schools of Biophysics. With Gopinath Kartha he solved the structure of collagen.

Download Full-text

The Use of Connected Masks for Reconstructing the Single Particle Image from X-Ray Diffraction Data. II. The Dependence of the Accuracy of the Solution on the Sampling Step of Experimental Data

Математическая биология и биоинформатика ◽

10.17537/2015.10.508 ◽

2015 ◽

Vol 10 (2) ◽

pp. 508-525 ◽

Cited By ~ 3

Author(s):

Н.Л. Лунина ◽

N.L. Lunina

Keyword(s):

Experimental Data ◽

Particle Image ◽

Expected Improvement ◽

Problem Solution ◽

Phase Problem ◽

X Ray Diffraction ◽

Sampling Step ◽

X Ray ◽

X Ray Crystallography ◽

Grid Points

Advances in the methodology of the X-ray diffraction experiments leads to a possibility to register the rays scattered by large isolated biological particles (viruses and individual cells) but not only by crystalline samples. The experiment with an isolated particle provides researchers with the intensities of the scattered rays for the continuous spectrum of scattering vectors. Such experiment gives much more experimental data than an experiment with a crystalline sample where the information is limited to a set of Bragg reflections. This opens up additional opportunities in solving underlying problem of X-ray crystallography, namely, calculating phase values for the scattered waves needed to restore the structure of the object under study. In practice, the original continuous diffraction pattern is sampled, reduced to the values at grid points in the space of scattering vectors (in the reciprocal space). The sampling step determines the amount of the information involved in solving the phase problem and the complexity of the necessary calculations. In this paper, we investigate the effect of the sampling step on the accuracy of the phase problem solution obtained by the method proposed earlier by the authors. It is shown that an expected improvement of the accuracy of the solution with the reducing the sampling step continues even after crossing the Nyquist limit defined as the inverse of the double size of the object under study.

Download Full-text