Direct methods (crystallography)
- Direct methods (crystallography)
-
In crystallography, direct methods are a family of methods for estimating the phases of the Fourier transform of the scattering density from the corresponding magnitudes. The methods generally exploit constraints or statistical correlations between the phases of different Fourier components that result from the fact that the scattering density must be a positive real number.
In two dimensions, it is relatively easy to solve the phase problem directly, but not so in three dimensions. The key step was taken by Hauptman and Karle, for which they were awarded the 1985 Nobel prize in Chemistry.
At present, direct methods are the preferred method for phasing crystals of small molecules having up to 1000 atoms in the asymmetric unit. However, they are generally not feasible by themselves for larger molecules such as proteins.[1][2]
Several software packages implement direct methods.
References
Wikimedia Foundation.
2010.
Look at other dictionaries:
Direct method — may refer to Direct method (education) for learning a foreign language Direct method (computational mathematics) as opposed to iterative method Direct methods (crystallography) for estimating the phases of the Fourier transform of the scattering… … Wikipedia
X-ray crystallography — can locate every atom in a zeolite, an aluminosilicate with many important applications, such as water purification. X ray crystallography is a method of determining the arrangement of atoms within a crystal, in which a beam of X rays strikes a… … Wikipedia
Electron crystallography — is a method to determine the arrangement of atoms in solids using a transmission electron microscope (TEM). Contents 1 Comparison with X ray crystallography 2 Radiation damage 3 Protein structures determined by electron crystallography … Wikipedia
Crystallographic image processing — (CIP) is a set of methods for determining the atomic structure of crystalline matter from high resolution electron microscopy (HREM) images obtained in a transmission electron microscope (TEM). The term was created in the research group of Sven… … Wikipedia
Prix Gregori Aminoff — Le prix Gregori Aminoff est un prix international créé en 1979 et délivré par l Académie royale des sciences de Suède dans le domaine de la crystallographie. Il récompense « une contribution documentée et individuelle dans le domaine de la… … Wikipédia en Français
Multi-wavelength anomalous dispersion — Multi wavelength anomalous diffraction (sometimes Multi wavelength anomalous dispersion; abbreviated MAD) is a technique used in X ray crystallography that facilitates the determination of the three dimensional structure of biological… … Wikipedia
Multiple isomorphous replacement — or MIR is the most common approach of solving the phase problem in X ray crystallography. This method is conducted by soaking the crystal of a sample to be analyzed with a heavy atom solution or co crystallization with the heavy atom. The… … Wikipedia
Détermination d'une structure cristalline — La détermination d une structure cristalline consiste, de manière générale, à déterminer, pour un cristal de structure inconnue, les paramètres de sa maille conventionnelle, son réseau de Bravais, son groupe d espace et la position des atomes… … Wikipédia en Français
Herbert A. Hauptman — Infobox Scientist name = Herbert A. Hauptman image width = caption = birth date = birth date and age|1917|2|14 birth place = New York City, New York, U.S.A. death date = death place = residence = citizenship = nationality = American ethnicity =… … Wikipedia
Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… … Universalium
