ExtraCreditHomework3KEY

# ExtraCreditHomework3KEY - Name KEY EID Extra Credit...

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Name: KEY EID: Extra Credit Homework #3 Complete questions below and hand in to a TA by the end of class, Friday, Sept. 16. 1. Binding a) Is a ligand with K d of 9 nM more tightly or weakly binding than one with K d of 26 nM? Calculate their K a values. The ligand with K d of 9 nM is more tightly binding. Recall the definition of K d (the dissociation constant ): K d = [P][L]/[PL] (where [P] is free protein, [L] is free ligand, and [PL] is protein-bound ligand). This equation states that the larger the numerator, the more free protein and ligand. Conversely, larger the denominator, the more protein-bound ligand. Recall that K a (the association constant ) is the reciprocal of K d : K a = 1/K d Therefore, for a K d of 9 nM, the K a is 0.11 nM -1 , and for a K d of 26 nM, the K a is 0.04 nM -1 . b) When the ligand concentration [L] is equal to the K d , what is true? Demonstrate this mathematically, starting with the equation ! " ! " ! " ! !" !" + = ! . Half of the ligand-binding sites are occupied.

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## This note was uploaded on 02/06/2012 for the course BIOCHEMIST 339K taught by Professor Keating-clay during the Spring '11 term at University of Texas.

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ExtraCreditHomework3KEY - Name KEY EID Extra Credit...

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