BERG/STRYER VI STUDY GUIDE CHAPTER 3 1. HOMEWORK 1-3, 5, 7, 10. Answers on p. C-2, solutions in back of COMPANION . Proteins can be purified using techniques that involve electrophoresis, chromatography, ultra-centrifugation, and other methods. You should understand the difference between electrophoresis with and without SDS, and know what SDS PAGE stands for. SDS PAGE is frequently used to obtain a quick estimate of a protein's molecular weight. What is isoelectric focusing ? (See Fig 3.11) Dialysis and gel filtration are separations on the basis of size. Gel filtration can produce good separations and can be used to estimate molecular weight if the protein is globular. Affinity chromatography can be an extremely effective way to purify certain proteins. Ion exchange is more useful with amino acids and peptides than with proteins, and gives a rather crude separation. 2. There are several different modes of ultracentrifugation , used for different purposes. Rate sedimentation (p. 76) gives a "quick and dirty" idea of the size of a protein or complex, in
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