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Loren McCune

What is the net charge of cysteine in pH 9 and 12 from its constituents pKas?

BeachLover62  Follow

What is the net charge of cysteine in pH 9 and 12 from its constituents' pKas?

I think the easiest way to approach this question (for any amino acid or in fact, any polyprotic substance) is to start by considering the fully protonated form of the substance that would exist at a pH well below the first pKa, say, pH = 0.

For cysteine, that would be carboxy group protonated (neutral), amino group protonated (+1) and side chain protonated (neutral), so an overall charge of +1.

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