Diffraction anomalous

A teclmique that employs principles similar to those of isomorphous replacement is multiple-wavelength anomalous diffraction (MAD) [27]. The expression for the atomic scattering factor in equation (B1.8.2h) is strictly accurate only if the x-ray wavelength is well away from any characteristic absorption edge of the element, in which case the atomic scattering factor is real and Filiki) = Fthkl V- Since the diffracted... 

Flendrickson W A 1991 Determination of macromolecular structures from anomalous diffraction of synchrotron radiation Soienoe 254 51-8... 

Phase information can also be obtained by Multiwavelength Anomalous Diffraction experiments... 

The intensity differences obtained in the diffraction pattern by illuminating such a crystal by x-rays of different wavelengths can be used in a way similar to the method of multiple isomorphous replacement to obtain the phases of the diffracted beams. This method of phase determination which is called Multiwavelength Anomalous Diffraction, MAD, and which was pioneered by Wayne Hendrickson at Columbia University, US, is now increasingly used by protein cystallographers. 

X-ray data are recorded either on image plates or by electronic detectors The rules for diffraction are given by Bragg s law Phase determination is the major crystallographic problem Phase information can also be obtained by Multiwavelength Anomalous Diffraction experiments... 

Hendrickson WA, Horton JR, LeMaster DM. Selenomethionyl proteins produced for analysis by multiwavelength anomalous diffraction (MAD) a vehicle for direct determination of three-dimensional structure. EMBO J... 

Membrane-integrated proteins were always hard to express in cell-based systems in sufficient quantity for structural analysis. In cell-free systems, they can be produced on a milligrams per milliliter scale, which, combined with labeling with stable isotopes, is also very amenable forNMR spectroscopy [157-161]. Possible applications of in vitro expression systems also include incorporation of selenomethionine (Se-Met) into proteins for multiwavelength anomalous diffraction phasing of protein crystal structures [162], Se-Met-containing proteins are usually toxic for cellular systems [163]. Consequently, rational design of more efficient biocatalysts is facilitated by quick access to structural information about the enzyme. 

Figure 11. Anomalous diffraction pattern of a small metallic particle, showing 2.46 A spots.

Ealick, S.E. (2000) Advances in multiple wavelength anomalous diffraction crystallography, Curr. Opin. Chem. Biol., 4, 495-499. 

Despite the knowledge that Friedel s law does not hold in anomalous diffraction and that the absolute polarity of the zinc sulfide structure had been determined, the idea that it is fundamentally impossible to determine the absolute... 

All these experimental results point unambiguously to a heterobimetallic catalytic centre in [NiFe] hydrogenases, which thus deserve their previously assigned name (Moura et al. 1988). Anomalous diffraction has been successfully used also to identify the selenium atom of the selenocysteine binding to the nickel atom in Dm. baculatum (Garcin et al. 1999). 

Multiwavelength anomalous diffraction Makes use of atoms within a protein that diffract X-rays anomalously. Commonly uses seleno-methionine residues in place of methionines. 

The multiple-wavelength anomalous diffraction method (MAD) relies upon sufficiently strong anomalously scattering atoms in the protein structure itself In this method, diffraction data must be collected at a number of different wavelengths, usually requiring data collection with... 

From a relatively small begiiming, nearly two decades ago (Guss et al., 1988 Murthy et al., 1988 Hendrickson et al., 1988, 1989), phase calculation using Multiple-wavelength Anomalous Diffraction (MAD) data has become more widespread and generally used. There are many reviews that cover diverse aspects of the process (Hendrickson, 1991 Smith, 1991 Ogata, 1998 Ealick, 2000). This review will concentrate on the most recent developments and experimental details, and is essentially an update to the author s earlier review (Krishna Murthy, 1996). 

To achieve analogy with MIR, the normal and anomalous diffraction parts for a reflection are expressed as separate quantities,... 

Hendrickson, W. A., et al. (1986). Structure of D-selenolanthionine determined directly from multiwavelength anomalous diffraction of bremstrahlung. Am. Crystallogr Assoc Series 2 (Abstract) 14,48. 

Krishna Murthy H. M. (1996). The use of multiple wavelength anomalous diffraction in ab initio phase determination. Method Mol. Biol. 56,127-152. 

La Fortelle, E. D. and Bricogne, G. (1997). Maximum-likelihood heavy-atom parameter refinement for multiple isomorphous replacement and multiwavelength anomalous diffraction methods. Method Enzymol. 276, 472 94. 

Ramakrishnan, V. and Biou, V. (1997). Treatment of multiwavelength anomalous diffraction data as a special case of multiple isomorphous replacement. Method Enzymol. 276, 538-557. 

Smith, J. L. (1991). Determination of three-dimensional structure by multiwavelength anomalous diffraction. Current Opin. Struct. Biol 1,1002-1011. 

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