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From: Christian.Pilger-!at!-bc.boehringer-ingelheim.com
To: meenatul;at;bom2.vsnl.net.in
Cc: chemistry-: at :-ccl.net
Subject: AW: Histidine
Date: Mon, 25 Mar 2002 07:41:56 +0100
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Dear Meena,

the way I do this is to inspect each HIS residue manually and have a look on
the surrounding amino acids in terms of ionization state and hydrogen bond
donor/acceptor capabilities. In many cases you get a good hint about where
to put the proton, especially if you have a GLU or an ASP in hydrogen
bonding distance, there is a good chance, that the HIS will form a salt
bridge, hence it carries protons on both nitrogens. In analogy you can make
a decision to put the proton on N(delta) or N(epsilon) depending on the
closeness of HB donors/acceptors. In cases, where I can not make a clear
estimate, I arbitrarily put the proton on N(delta).

Cheers,

Christian
________________________________________________________________

   Dr. Christian Pilger
   Dept. Chemical Research / Structural Research
   K91-00-10
   Boehringer Ingelheim Pharma KG
   D-88397 Biberach/Germany
   Phone: 07351-545749
   Fax:     07351-5497924
   mailto: christian.pilger- at -bc.boehringer-ingelheim.com