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Peptide charges in basic solution.?

Peptide charges in basic solution.? - Peptide Forum

Peptide charges in basic solution.? - Peptide Forum. Ask and discuss questions on peptide protocols, custom peptide synthesis, peptide identification and peptide sequencing.


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Old 09-13-2012, 03:15 AM
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Default Peptide charges in basic solution.?



What is total charge of a Val-His-Asp tripeptide @ pH 11?

Val NH3 pKa = 9.62
His pKr = 6.00
Asp pKr = 3.65 & pKa = 1.88

If I'm understanding this correctly, at pH 11, given those pKa and pKr values, both amino groups would be deprotonated. Long before that, both carboxyl groups would also be deprotonated, so the answer should be -2. Is this correct?

Also, a question that the book doesn't answer and I don't see my Prof. until Friday so I;m asking here. Being that the N-terminus is now farther away from the C-terminus, does this not affect pKa values for the C-terminus carboxl group?
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Old 09-13-2012, 03:34 AM
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Thumbs up Re: Peptide charges in basic solution.?

Yes your answer, as well explanation is correct. Above peptide having -2 Charge because of both the carboxyl group of aspartic acid.
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