science

Multi-wavelength anomalous diffraction

Multi-wavelength anomalous diffraction is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Multi-wavelength anomalous diffraction rather than just read about it. In short: 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.

Key takeaways

Multi-wavelength anomalous diffraction belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Multi-wavelength anomalous diffraction to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Multi-wavelength anomalous diffraction from memory before moving on to harder problems.

Reference excerpt

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. 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) was based were developed by Jerome Karle, work for which he was awarded the 1985 Nobel Prize in Chemistry (along with Herbert Hauptman). Compared to the predecessor SAD, MAD has greatly elevated phasing power from using multiple wavelengths close to the edge. However, because it requires a synchrotron beamline, a longer exposure (risking radiation damage), and only allows a limited choice of heavy atoms (those with edges reachable by a synchrotron), MAD has declined in popularity relative to SAD.

See also Single wavelength anomalous dispersion (SAD) Multiple isomorphous replacement (MIR) Anomalous scattering Anomalous X-ray scattering Patterson map

References

Further reading Hendrickson WA (1985). "Analysis of Protein Structure from Diffraction Measurement at Multiple Wavelengths". Transactions of the ACA. 21. Karle J (2009). "Some developments in anomalous dispersion for the structural investigation of macromolecular systems in biology". International Journal of Quantum Chemistry. 7: 357–367. doi:10.1002/qua.560180734. Karle J (1989). "Linear Algebraic Analyses of Structures with One Predominant Type of Anomalous Scatterer". Acta Crystallographica A. 45 (4): 303–307. Bibcode:1989AcCrA..45..303K. doi:10.1107/s0108767388013042. PMID 2559755. Pahler A, Smith JL, Hendrickson WA (1990). "A Probability Representation for Phase Information from Multiwavelength Anomalous Dispersion". Acta Crystallographica A. 46 (7): 537–540. Bibcode:1990AcCrA..46..537P. doi:10.1107/s0108767390002379. PMID 2206480. Terwilliger TC (1994). "MAD Phasing: Bayesian Estimates of FA". Acta Crystallographica D. 50 (Pt 1): 11–16. Bibcode:1994AcCrD..50...11T. doi:10.1107/s0907444993008224. PMID 15299471. Terwilliger TC (1994). "MAD Phasing: Treatment of Dispersive Differences as Isomorphous Replacement Information". Acta Crystallographica D. 50 (Pt 1): 17–23. Bibcode:1994AcCrD..50...17T. doi:10.1107/s0907444993008236. PMID 15299472. Fourme R, Shepard W, Kahn R, l'Hermite G, de La Sierra IL (1995). "The Multiwavelength Anomalous Solvent Contrast (MASC) Method in Macrocolecular Crystallography". Journal of Synchrotron Radiation. 2 (Pt 1): 36–48. Bibcode:1995JSynR...2...36F. doi:10.1107/S0909049594006680. PMID 16714785. de la Fortelle E, Bricogne G (1997). "Maximum-likelihood heavy-atom parameter refinement for multiple isomorphous replacement and multiwavelength anomalous diffraction methods". Macromolecular Crystallography Part A. Methods in Enzymology. Vol. 276. pp. 472–494. doi:10.1016/S0076-6879(97)76073-7. ISBN 978-0-12-182177-7. PMID 27799110. Hendrickson WA, Ogata CM (1997). "Phase determination from multiwavelength anomalous diffraction measurements". Macromolecular Crystallography Part A. Methods in Enzymology. Vol. 276. pp. 494–523. doi:10.1016/S0076-6879(97)76074-9. ISBN 978-0-12-182177-7. PMID 27799111. Bella J, Rossmann MG (1998). "A General Phasing Algorithm for Multiple MAD and MIR Data". Acta Crystallographica D. 54 (2): 159–174. Bibcode:1998AcCrD..54..159B. doi:10.1107/s0907444997010469. PMID 9761882. 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.

External links 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

Computer programs 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". Review of Scientific Instruments. 63 (1): 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". Journal of Applied Crystallography. 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 Crystallographica D. 54 (Pt 5): 799–804. Bibcode:1998AcCrD..54..799S. doi:10.1107/S0907444997018805. PMID 9757093. SHELX — Sheldrick GM (1998). "SHELX: applications to macromolecules". In S Fortier (ed.). Direct methods for solving macromolecular structures. Dordrecht: Kluwer Academic Publishers. pp. 401–411. ISBN 0-7923-4949-0.{{cite book}}: CS1 maint: publisher location (link)

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.

Worked examples

Example 1 — a first encounter with Multi-wavelength anomalous diffraction

Start with the simplest possible case. Write down what Multi-wavelength anomalous diffraction claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Multi-wavelength anomalous diffraction before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Multi-wavelength anomalous diffraction ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Multi-wavelength anomalous diffraction

In research: Multi-wavelength anomalous diffraction appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Multi-wavelength anomalous diffraction in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Multi-wavelength anomalous diffraction is common in secondary-school and first-year university syllabi. It links to neighbouring topics Crystallography, so understanding it makes those chapters shorter.
In everyday life: Look for Multi-wavelength anomalous diffraction outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Multi-wavelength anomalous diffraction in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Multi-wavelength anomalous diffraction means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Multi-wavelength anomalous diffraction out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Multi-wavelength anomalous diffraction in simple terms?

Why does Multi-wavelength anomalous diffraction matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Multi-wavelength anomalous diffraction?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Multi-wavelength anomalous diffraction.