595C00Ex1 - Chemistry 595C Fall 2000 Exam 1 Written Answers...

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Chemistry 595C Fall 2000 Exam 1 Written Answers 1. In the use of NMR to determine the structure of biomolecules the structural information is obtained primarily by measuring the nuclear Overhauser effect. a) Very briefly describe what the nuclear Overhauser effect results from and to what degree the effect depends upon distance. Give the maximum practical observable distance. b) Solving macromolecular structures by X-ray crystallography depends upon measurement of the electron density at each point within the unit cell. In turn, those measurements depend upon the intensities of the diffracted X-rays and the phases of the diffracted X-rays. Briefly describe two common methods (MIR and MAD) that can be used to solve the &phase problem.± c) Contrast the use of NMR and X-ray crystallography as applied to biomacromolecules. Address in particular the issues of any limitations on the size of the macromolecules whose structure can be determined by either technique; what types of information that can be determined by one technique and not the other and whether both techniques always give the same structure for a particular macromolecule (both proteins and nucleic acids). 2. From the amino acid structures listed below, answer the following questions:
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a. What is the name of amino acid A? ___________________________ b. Which of the above amino acids has the highest isoelectric point? ________________ c. Which of the above amino acids is classified as a basic amino acid? _______________ d. Which of the above amino acids absorbs light centered at 280 nm? _______________ e. What is the name of amino acid D? ______________________________ f. What is the name of amino acid B? _______________________________ g. Draw the structure of tryptophan showing the charge on the molecule as it would be at pH 7. h. Draw the structure of the dipeptide pro-his (at pH 7) i. Name 2 sulfur containing amino acids _________________________ ________________________ j. What is the approximate pK of the side chain amino group of lysine? _____________ 3. a) What is meant by the statement &stacking interactions are important in stabilizing the structures of nucleic acids±? Describe the nature of these interactions and give examples for both DNA and RNA molecules. (1/3 p) b) Which of the following stacking interactions will provide more stability : purine-purine or pyrimidine-pyrimidine? (1/3 p) c) Bound metals are often found in RNA structures. What kinds of roles can the metals play?
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(1/4 p) d) Hydrogen bonding also plays a role in nucleic acid structure stabilization. In what important ways does it differ from stacking and metal ion interactions? 5.
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This note was uploaded on 04/25/2010 for the course LIFE SCIEN Genetics taught by Professor Chen during the Spring '10 term at UCLA.

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595C00Ex1 - Chemistry 595C Fall 2000 Exam 1 Written Answers...

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