Message-Id: <199701291419.JAA24827@chem.bu.edu>
Date: Wed, 29 Jan 1997 09:22:06 +0000
From: laursen@bu.edu (Richard Laursen)
Subject: RE: pKa of Asn side chain
To: Recipients of ABRF List <abrf@aecom.yu.edu>
Dear Gottfried,
Thanks for enlightening everyone about our two answers, both of which are
correct. One man's acid (RCONH2) is another man's base.
It's like the three blind men who were asked to feel and then describe an
elephant. The first felt the elephant's side and said, "An elephant is
very much like a wall." The second felt a leg and said, "An elephant is
very much like a tree." The third said, after feeling its trunk, "An
elephant is very much like a snake"......
Richard Laursen
>Hi all,
>
>since there has been two different answers given for the pKa of Asn side
>chain, maybe a little extra explanation about the subject :
>
>I indicated a pKa of about 17, corresponding to the ionization of:
>RCONH2 <----> RCONH(-), meaning the acidity of the side chain functional
>group taken as amide.
>
>The values given by Richard Laursen correspond to the other possible
>ionization :
>RCONH3(+) <-----> RCONH2, meaning the acidity of the protonated amide
>function.
>
>I hope this avoids eventual misunderstandings concerning this question.
>
>Gottfried Proess
>Eurogentec Bel S.A.
>Parc Scientifique du Sart Tilman
>B-4102 Seraing
>Belgium
>Tel.: + 32 4 366 61 07
>Fax: + 32 4 365 51 03
>E-Mail: g.proess@eurogentec.be
Richard A. Laursen
Department of Chemistry
Boston University
590 Commonwealth Ave.
Boston, MA 02215
Tel (617) 353-2491; FAX (617) 353-6466
email: <laursen@bu.edu>