[gmx-users] Re: How to restrain dihedral angles to reserve the tacticity?

Javier Cerezo jcb1 at um.es
Thu May 23 16:48:18 CEST 2013

Improper dihedrals (section 4.2.11) can be used to retain chirality 
within unitied atoms models.


El 23/05/13 13:48, Abhishek Acharya escribió:
>> Dear Acharya,
>> Thank you very much for this quick reply. According to your suggestion, I
>> measure the main chain dihedral angles, only to find that same values are
>> obtained for both isotactic and syndiotactic ones.
> That is obvious i think for a correct tacticity polymeric chain.
>> Therefore, this way can
>> not distinguish tacticity of polymer chains.
> I don't understand what is the need as the atomic positions should be the
> enough to distinguish tacticity.
>> For a good initial
>> configuration (with a correct tacticity), due to higher energy barrier,
>> the
>> tacticity of polymer can be naturally reserved using the improper
>> dihedrals
>> or restrained dihedrals as you suggest during the MD simulation. However,
>> for a bad initial configuration (with an incorrect tacticity), your way
>> seems not to be able yield the desirable results. Could you provide
>> further
>> help, please? Thanks a lot.
> The suggestion was assuming a good initial configuration. However, i do
> not have sufficient expertise to further comment on this.
> Cheers
> Abhishek

PhD Student
Physical Chemistry
Universidad de Murcia
Murcia (Spain)
Tel: (+34)868887434

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