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# RQ12 - C f all 2010 R eading Quiz R Q 1 2 H arrison Ch 8...

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CHEN 4820 fall 2010 Reading Quiz RQ12 Harrison Ch 8 (precipitation) Pledge: On my honor, I have neither given nor received aid on this quiz. Print name: _________________________________________ Signature: __________________________________________ Quiz: Q1. The Cohn Equation describes the salting out behavior of proteins in aqueous solution as a function of the ionic strength of the solution, I. Pick the correct form of the Cohn Equation. Here, S is the solubility of the protein, and ! and K are constants for a given solution pH, temperature, etc. and for a given salt choice as the precipitating agent. A Log S = ! + K* I B S = ! - K* I C Log S = ! - K* I Ans = C. The Cohn equation predicts that the log of solubility is a straight line with negative slope, ie that the solubility goes down as the ionic strength of the salt goes up. The ionic strength is defined by I = ! * (C + *z + + C - * z - ) where C + and C - are the molar concentrations of the cation and anion of the salt, and z + and z - are the charge of the cation and the anion. Q2. Pick the correct sequence of stages in forming a precipitate. A Initial mixing, growth by diffusion, growth by fluid motion, nucleation B Initial mixing, nucleation, growth by diffusion, growth by fluid motion C Initial mixing, growth by diffusion, nucleation, growth by fluid motion Ans = B. No mixing, however vigorous, can instantly produce a uniform solution at the molecular level. The Initial

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RQ12 - C f all 2010 R eading Quiz R Q 1 2 H arrison Ch 8...

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