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Predict how the pKa of cysteine would be impacted when it is a. near a lysine...

Predict how the pKa of cysteine would be impacted when it is

a. near a lysine sidechain

b. sequestered from solvent (water)

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Answer #1


Cysteine is sulphur containing amino acid and its pKa value in acid group is 1.96 and in basic group is 8.18. PI value is average of these two that is 5.07 but it will impacted as asked situation

a. Lysine is basic amino acid as there is amino side chain so its pKa value is more near 11. So when cysteine will be near lysine side chain then resultant pKa will increase and that will makes cysteine more basic than its original.

b. pKa value of cysteine would be unchanged when sequestered from water as water is neutral molecule it would not effect the acidic or basic properties of amino acid and amino acid will be in zwitterionic form in water.

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