AMBER Archive (2005)

Subject: Re: AMBER: How to fix the torsion angles during energy minimization

From: Ananda Rama Krishnan Selvaraj (ananda.selvaraj_at_chemie.uni-halle.de)
Date: Fri Apr 01 2005 - 06:54:18 CST

Hello Pete,
               thanks for your response. actually i am using Gaussian
program for this partial optimization problem. the problem is the
following, in my system totally 150 atoms ( butane only a example
molecule which i have taken for simplicity to explain my problem) are
there. so when i use gaussian with some sohisticated method it needs
lot of computational effort. moreover i am interested in relative
enrgey of the conformers not the absolute energy values.

so that i want to do same type calculations using amber force field.
to reduce the computational effort.

also ..i am expecting some more good suggestions from the Amber
Community..

thanks
Anandaramakrishnan

ANANDA RAMA KRISHNAN .S
PhD Student
c/o. Prof. Rudolf Friedemann
Department of organic chemistry
Martin Luther university
Kurt-mothes-str.2
D-06120 Halle (saale),Germany
e-mail: ananda.selvaraj_at_chemie.uni-halle.de
Ph(lab) : (+int) 345 - 5525683

----- Original Message -----
From: Peter Gannett <pgannett_at_hsc.wvu.edu>
Date: Friday, April 1, 2005 2:32 pm
Subject: Re: AMBER: How to fix the torsion angles during energy
        minimization

> Ananda:
>
> I'm not sure why you want to do this, but it seems to me you may want
> to use a different program for this such as gaussian or gamess.
>
> Pete
>
> >>> ananda.selvaraj_at_chemie.uni-halle.de 4/1/2005 1:42:27 AM >>>
> Dear Amber Users,
> i am new to amber. i am interested to make energy
> minimization with torsional constraints using amber7.
>
> To do this i have tried with simple butane molecule.
>
> with this molecule, i have started with three different starting
> conformations like Gauche,Eclipsed and Trans.
>
> finally, Gauche and Eclipsed conformations given the same energy
> 3.2
> kcal/mol with torsion angle of C1-C2-C3-C4 : 65.8 degree and trans
> conformation given 2.3 kcal/mol, with torsion angle C1-C2-C3-
> C4:180
> degree.
>
> but i am interested to calculate the exact energy of the gauche or
> eclipsed or trans conformations. actually, i want to do partial
> energy minimization by fixing the C1-C2-C3-C4 torsion angle to a
> particular value and all other parameters should be optimise
> during
> the energy minimization.
>
> is it possible by amber. could any one give the answer with proper
> input format.
>
> thanks
> S.Anandaramakrishnan
>
>
>
>
>
>
>
>
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