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X-ray crystallography: Quiz


Question 1: What does the following picture show?

  A protein crystal structure at 2.7 Å resolution. The mesh encloses the region in which the electron density exceeds a given threshold. The straight segments represent chemical bonds between the non-hydrogen atoms of an arginine (upper left), a tyrosine (lower left), a disulfide bond (upper right, in yellow), and some peptide groups (running left-right in the middle). The two curved green tubes represent spline fits to the polypeptide backbone.
  A protein crystal seen under a microscope. Crystals used in X-ray crystallography may be smaller than a millimeter across.
  Three methods of preparing crystals, A: Hanging drop. B: Sitting drop. C: Microdialysis
  Ribbon diagram of the structure of myoglobin, showing colored alpha helices. Such proteins are long, linear molecules with thousands of atoms; yet the relative position of each atom has been determined with sub-atomic resolution by X-ray crystallography. Since it is difficult to visualize all the atoms at once, the ribbon shows the rough path of the protein polymer from its N-terminus (blue) to its C-terminus (red).

Question 2: An intermediate case is ________ in which the subunits are arranged periodically in at least one dimension.
Protein structureFiber diffractionX-ray crystallographyBiological small-angle scattering

Question 3: The method also revealed the structure and functioning of many biological molecules, including vitamins, drugs, proteins and nucleic acids such as ________.

Question 4: In an X-ray diffraction measurement, a ________ is mounted on a goniometer and gradually rotated while being bombarded with X-rays, producing a diffraction pattern of regularly spaced spots known as reflections.
CrystalCrystal structureSolidCarbon

Question 5: The most common metal used is ________, which can be kept cool easily, due to its high thermal conductivity, and which produces strong Kα and Kβ lines.

Question 6: Single-crystal diffraction is also used in the ________, due to recent problems with polymorphs.
Clinical trialDrug discoveryPharmaceutical drugPharmaceutical industry

Question 7: The brightest and most useful X-ray sources are ________; their much higher luminosity allows for better resolution.
SynchrotronCERNSLAC National Accelerator LaboratoryParticle accelerator

Question 8: Single-slit experiments in the laboratory of ________ suggested the wavelength of X-rays was about 1 Angström.
Max BornMax PlanckWerner HeisenbergArnold Sommerfeld

Question 9: The three-dimensional real vector q represents a point in ________, that is, to a particular oscillation in the electron density as one moves in the direction in which q points.
Reciprocal latticeFourier transformCrystallographyLattice (group)

Question 10: However, X-rays are composed of ________, and thus are not only waves of electromagnetic radiation but also exhibit particle-like properties.
AtomElectronStandard ModelPhoton


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