BIOL 200 Lecture Notes - Lecture 27: Catenin, Corepressor, Cell Fractionation
25 Jan 2017
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Document Summary
If rate-zonal centrifugation is spinned long enough and the density of the medium is high enough, all the particles will eventually settle to density equal to themselves: density gradient yields the purest dna, since dna is very dense. Dna is negative, attracted towards the cathode (+); thus separation is straightforward. Proteins have variable composition, charge results from addition of all the charges of the protein; most proteins have a negative charge and goes toward the cathode. Modify ph to deprotonate proteins; negative charge moves faster, less mass moves faster. This method retains protein structure; proteins are separated in this native state, properly folded; can be retrieved to test enzymatic activity via assays. Denature proteins completely with a strong detergent, sds; now shape has no influence. Sds: negatively charged detergent that binds hydrophobic residues of the polypeptide (which is inside the structure), causing its unfolding + denaturation all proteins become negatively charged.
