- 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 macromolecules (e.g., DNA, drug receptors) via solution of the phase problem. This method can be applied in cases where two crystal structures exist -- one structure for which one or more atoms has been replaced by heavy-atoms (in order to cause significant anomalous scattering from incoming X-rays) and one for which no heavy-atom replacement has been made. The most commonly used heavy atom used for phase determination is selenium: Selenomethionine is a heavy-atom derivative of the amino acid methionine, which can be inserted through the use of selective media during protein expression. Anomolous diffraction is then recorded at different wavelengths of coherent X-ray light at a synchrotron facility.
MAD was developed by Wayne Hendrickson while working as a postdoctoral researcher under Jerome Karle at the United States Naval Research Laboratory.  The mathematics upon which MAD (and progenitor Single-wavelength Anomalous Diffraction) were based were developed by Jerome Karle, work for which he was awarded the 1985 Nobel Prize in Chemistry (along with Herbert Hauptman).
- Multi-wavelength Anomalous Dispersion (MAD)
- Single wavelength anomalous dispersion (SAD)
Two methods for providing the needed phasing information by introducing heavy atoms into isomorphous crystals:
- Multiple isomorphous replacement (MIR); and
- Single isomorphous replacement with anomalous signal (SIRAS)
- ^ Hendrickson W, Ogata C (1997). "Phase determination from multiwavelength anomalous diffraction measurements". Meth Enzymol. Methods in Enzymology 276: 494–523. doi:10.1016/S0076-6879(97)76074-9. ISBN 9780121821777.
- ^ Hendrickson WA (1985). "Analysis of Protein Structure from Diffraction Measurement at Multiple Wavelengths". Trans. ACA 21.
- Hendrickson WA (1985). "Analysis of Protein Structure from Diffraction Measurement at Multiple Wavelengths". Trans. ACA 21.
- Karle J (1980). "Some Developments in Anomalous Dispersion for the Structural Investigation of Macromolecular Systems in Biology". International Journal of Quantum Chemistry: Quantum Biology Symposium 7: 357–367.
- Karle J (1989). "Linear Algebraic Analyses of Structures with One Predominant Type of Anomalous Scatterer". Acta Cryst. A45: 303–307.
- Pahler A, Smith JL, Hendrickson WA (1990). "A Probability Representation for Phase Information from Multiwavelength Anomalous Dispersion". Acta Cryst. A46: 537–540.
- Terwilliger TC (1994). "MAD Phasing: Bayesian Estimates of FA". Acta Cryst. D50: 11–16.
- Terwilliger TC (1994). "MAD Phasing: Treatment of Dispersive Differences as Isomorphous Replacement Information". Acta Cryst. D50: 17–23.
- Fourme R, Shepard W, Kahn R, l'Hermite G, de La Sierra IL (1995). "The Multiwavelength Anomalous Solvent Contrast (MASC) Method in Macrocolecular Crystallography". J. Synchrotron Rad. 2: 36–48. doi:10.1107/S0909049594006680.
- de la Fortelle E, Bricogne G (1997). "Maximum-Likelihood Heavy-Atom Parameter Refinement for Multiple Isomorphous Replacement and Multiwavelength Anomalous Diffraction Methods". Methods in Enzymology. Methods in Enzymology 276: 472–494. doi:10.1016/S0076-6879(97)76073-7. ISBN 9780121821777.
- Hendrickson WA, Ogata CM (1997). "Phase Determination from Multiwavelength Anomalous Diffraction Measurements". Methods in Enzymology. Methods in Enzymology 276: 494–523. doi:10.1016/S0076-6879(97)76074-9. ISBN 9780121821777.
- Bella J, Rossmann MG (1998). "A General Phasing Algorithm for Multiple MAD and MIR Data". Acta Cryst. D54: 159–174.
- Guss JM, Merritt EA, Phizackerley RP, Hedman B, Murata M, Hodgson KO, Freeman HC (1989). "Phase determination by multiple-wavelength X-ray diffraction: crystal structure of a basic blue copper protein from cucumbers". Science 241 (4867): 806–811. Bibcode 1988Sci...241..806G. doi:10.1126/science.3406739. PMID 3406739.
- MAD phasing — an in depth tutorial with examples, illustrations, and references.
- HHMI Bio for Wayne Hendrickson
- Wayne Hendrickson Home Page
- Hendrickson Laboratory Summary of Research
- Jerome Karl Nobel Biography
- NRL Recognition of Nobel Prize
- The SSRL Absorption Package — Brennan S, Cowan PL (1992). "A suite of programs for calculating x-ray absorption, reflection and diffraction performance for a variety of materials at arbitrary wavelengths". Rev. Sci. Instrum. 63: 850. Bibcode 1992RScI...63..850B. doi:10.1063/1.1142625.
- CHOOCH — Evans G, Pettifer RF (2001). "CHOOCH: a program for deriving anomalous-scattering factors from X-ray fluorescence spectra". J. Appl. Cryst. 34: 82–86. doi:10.1107/S0021889800014655.
- Shake-and-Bake (SnB) — Smith GD, Nagar B, Rini JM, Hauptman HA, Blessing RH (1998). "The use of Snb to determine an anomalous scattering substructure". Acta Cryst D 54 (Pt 5): 799–804. doi:10.1107/S0907444997018805. PMID 9757093.
- SHELX — Sheldrick GM (1998). "SHELX: applications to macromolecules". In S Fortier. Direct methods for solving macromolecular structures. Dordrecht: Kluwer Academic Publishers. pp. 401–411. ISBN 0-7923-4949-0.
Tutorials and examples
- Evans, Gwyndaf (October 1994). "The method of Multiple wavelength Anomalous Diffraction using Synchrotron Radiation at optimal X-ray energies: Application to Protein Crystallography". PhD Thesis. University of Warwick. http://www.gwyndafevans.co.uk/thesis-html/thesis.html.
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