Subject: Re: CCL:Thermal chemistry involves amino acid in H2O

From: Andreas Klamt <klamt:at:cosmologic.de>
Date: Tue, 02 Nov 2004 07:45:24 +0100

Dear Jun,

amino acids in water obviously are complicated species because they 
typically exist as zwitterions. Hence for accurate thermochemistry you 
have to take those into account. The problem is that you need a very 
good level of quantum chemistry to get a good value for the energy 
difference of  neutral and zwitterionic state, and then obviously also a 
good one for the difference between amino acids and the reaction 
products. I am afraid that coupled cluster methods may be required, if 
you can afford them. Perhaps you can do these as single points on DFT 
geometries.

Thus I suggest that you first do the thermochemistry the gasphase. Then 
use our COSMOtherm program to get the solvation free energies of the 
educts and products. Thus you finally should end up at the 
thermochemistry in water.

Regards

Andreas

Deng, Jun wrote:

>Dear all:
>
>I am interested in calculating heat of reaction in water involving amino acid.  May I ask your suggestion on how to get accurate result?  
>
>Thank you very much in advance!
>
>Jun Deng
>
>
>
>
>
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-- 
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Dr. Andreas Klamt
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