Multi-wavelength anomalous dispersion

The tunability of synchrotron radiation allows for data collection at or near the x-ray absorption edge of anomalous scatterers present in the protein or crystal to provide experimental phase information. Using techniques such as multi-wavelength anomalous dispersion (MAD) and single-wavelength anomalous diffraction (SAD) researchers are now able to solve macromolecular structures in a matter of days or weeks, a process that required months, or even years, a decade ago. 

Nakagawa A, Higuchi Y, Yasuoka N, Katsube Y, Yagi T (1990) S-class cytochromes c have a variety of folding patterns structure of cytochrome c-553 from Desulfovibrio vulgaris determined by the multi-wavelength anomalous dispersion method. J Biochem 108 701— 703... 

Crystals from selenium-methionine- and/ or selenium-cysteine-labeled proteins can be studied by multi-wavelength anomalous dispersion (MAD) phasing techniques that can facilitate the solution of an X-ray crystal structure from a single crystal form [11]. However, if in vivo expression systems are used to prepare selenium-labeled proteins, amino acid metabolism and the toxicity of Se-methionine can result in low protein yields and low incorporation rates. 

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