Subject: Re: CCL:Global minimum (philosophical) problems...

From: Gregory Nikiforovich <[email-masked]>
Date: Tue, 7 Nov 1995 15:08:03 -0600 (CST)

On Tue, 7 Nov 1995, Victor M. Rosas Garcia wrote:

> For the global minimum, we could easily prove or disprove:
> "This particular conformer is higher in energy than the one we call 'global
> minimum'."
> By the same token, for a distribution:
> "This particular conformer has an energy higher than our cutoff limit of
> interest, (so we don't have to include it in the distribution)."
> 

	Since I like philosophical problems, let me comment. As far as we
 are interested in conformers (like in conformational search problem), energy
 is just a target function, and energy minimization is a way to find a
 conformer, i.e., a particular 3D arrangement of atoms/functional groups. If
 you look at the problem from this side, you would notice that several very
 similar 3D arrangements may possess different energies. On the other hand,
 some very different 3D arrangements can possess almost identical energies
 (e.g., enantiomers). So the true task of conformational search is not to find
 all conformers within a given cutoff; it is to find all different 3D 
 arrangements within a given energy cutoff. This task is much more realistic,
 since the possibility of missing a really different 3D arrangement during any
 search is less than to miss a minimum close to "the global" one in energy.
 However, it is not philosophy any more...

 	Best wishes.

Gregory V. Nikiforovich                                   Phone (314) 935-4677
Research Professor                                        Fax   (314) 935-4979
Center for Molecular Design                            E-mail address:
Washington University                                  [email-masked]
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St.Louis, MO 63130