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The structure and function of proteins in your body are incredibly sensitive to changes in \PH . If a solution is too acidic or basic , a protein...

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Can I have help with this problem it's 3 parts with part b having 2 subsections

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12 . The structure and function of proteins in your body are incredibly sensitive to changes in
\PH . If a solution is too acidic or basic , a protein can denature , or degrade . During each step
of the protein purification process , it is essential to keep the protein " happy " in a compatible
\buffer solution which mitigates significant changes in PH .
( 2 ) You run a thermal shift assay and determine that your desired protein is most stable
at PH1 7.70 . You have a variety of weak acids at your disposal . The acids and their p<a
values at 25 Care : MOPS ( PRA = 7. 18 ) , HEPES ( P <= = 7.56 ), TRIS ( PK<= = 8.07 ),
and CHES ( PK= = 9.39 ) . Which weak acid could you use in a buffer that is most likely
to protect your protein from degradation due to pit fluctuations ? Explain in a sentence
Or two . ( Hint : Justify your decision using the Henderson- [Tasselbalch equation. )
( b ) Your lab partner used the last of the acid you selected above . Fortunately , you have
in mind a suitable substitute for your protein ! Before using a stock solution of IES
( a welcome abbreviation of N - Tris ( hydroxymethy ! ) methyl - 2 - aminoethanesulfonic acid ) ,
"you decide to test its PHI and find that it's 7.45 . The pKa of TES at 25 C is 7.55 .
( 1) Would you want to use concentrated HICI or NaOH in order to adjust the pil of
the stock solution to 7 . 70 ?
CHEM 132
Chapter 17: Additional Aspects of Acid- Base Equilibria
Page 4

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( 11 ) Suppose you have 5 M solutions of both Na OH and HICI . What volume of your
selected reagent would you need to use in order to change the PHI from 7 .45 to 7.70
in 2 I of a 200 mM IES stock solution ?
( C ) Oftentimes , purification protocols are performed at 4 Cas lower temperatures help
prevent degradation of the desired protein . Should you adjust the PHI of your buffer
solution before or after cooling it to 4 C ? Why ? ( Hint : Recall Question & from Problem
Set 2 . )
CHEM 132
Chapter 17: Additional Aspects of Acid- Base Equilibria
Page 5

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