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Topic: pHi of a peptide (URGENT)  (Read 4467 times)

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Offline Rayan

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pHi of a peptide (URGENT)
« on: September 07, 2005, 06:19:19 AM »
Hello,

say we have this a decapeptide

glu-arg-pro-asp-met-cys-val-hist-trp-cys
                   |           |                      |
                  NH2       |___S_____S____|

we were asked to calculate the pHi of this peptide so do we just take each amino acid alone and calculate its pHi?

we we given the Pka of alpha COOH, beta and gamma COOH, alpha NH2, epsilon NH2, and R of hist and arg. what does R mean?!!

Offline sdekivit

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Re:pHi of a peptide (URGENT)
« Reply #1 on: September 07, 2005, 11:45:04 AM »
i think they mean with R the restgroup of the aminoacids, thus for arginine the NH2(+)-groups and for histidine the ring structure. Thus the side chains.

Remeber the common structure of amino acids:

(+)H3N - CR - COO(-) (at physiologic pH)

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