Which feature is NOT a requirement of the procedure for determining a protein\'s

Question

Which feature is NOT a requirement of the procedure for determining a protein's structure by X -ray crystallography? A1. The crystal must diffract an X-ray beam to produce a diffraction pattern of spots. A2. The preferred bond lengths of atoms in amino acids and the electron density map of the protein must be already known to interpret the experimental data from X-ray crystallography. A3. The protein molecules must assemble into a crystal where the molecules are aligned in the same orientation. A4. The spots in the diffraction pattern must be observed to deduce the electron density map in the crystal. A5. All of the above arc required. Which statement is FALSE regarding techniques of structure determination? A1. X-ray crystallography deduces the location of electrons in the crystal. A2. NMR spectroscopy deduces the distances between certain atoms in the protein. A3. Electron microscopy would be the best suited technique for obtaining atomic-level detail of structure in small, highly flexible proteins. A4. Prior knowledge of the sequence of the protein of interest is important for the success of a structure determination experiment. A5. All of the above are true.

Explanation / Answer

Answer M4-HW-9 (A5) all of the above is required

X-ray crystallography is a high resolution microscopy which helps in studying the atomic structure of protein and its functions.

A1) A protient crystal acts as a 3 dimentional diffracting medium and diffracts x-rays into characteristic pattern of spots which show the distribution of electorns in the protein.

A2) The accuracy of the data depends on the two wave properties of X-rays, Known as an Amplitude and a phase. The amplitude can be gained from experimental data where as the phase information is lost. Hence the some information about the atomic model should be know for the experiment data to b co-related with.

A3) x-ray crystallography hepls in studying the atomic struture (including details of ions, ligands, inhibitors and other molecules). A well ordered protien crystal yeilds a High resolution and detailed structure as a result. Flexible protiens are difficult to study as this method relies on alignment of molecules in exactly same orientation (well ordered)

A4) The crystal acts as a 3 dimentional diffracting medium. It diffracts the x-rays into characteristic pattern of spots which show the distribution of electorns in the protein.

Answer M4-HW-10 (A3) False

Electron microscopy works for large protiens or macromolecular complexes. NMR spectroscopy on other hand is a good tool for studying flexible protients as the protiens is studied in solution. Therefore NMR spectroscopy would be best suited for obtining atomic level detail of structure in small and highly flexible protiens.

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