Quoting Piotr Cieplak <cieplak.cgl.ucsf.edu>:
> This would go beyond the general philosophy of molecular mechanics,
> where the whole system is build from simple basic units.
> Going along Francois's line we would need totally different set of charges
> for let's say GLY-ALA and ALA-GLY (all L-type).
OK
I understand this would be "too much" for an _empirical_ force field, would
multiply the number of FF parans and units, and/or difficult to set this type
of force field (might not be needed also ?).
However, it is known that two diastereoisomers 'can' have two different global
minima (easy to characterize by NMR, HPLC or even TLC!). Even for small organic
molecules which present only two different asymetric carbons, the change induced
by the chirality [for diastereoisomers (and not enantiomers, once again)] is
sometimes _very_ impressive. It would be easy to check this by studying (for
instance) the global minima of two diastereoisomers of threonine...
Regards, Francois
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Received on Fri Sep 23 2005 - 08:53:00 PDT
