Subject: MMFF94 validation in Sybyl and Cerius2

From: "Dr Adrian Stevens" <[email-masked]>
Date: Wed, 23 Jun 1999 09:39:06 +0100

Dear All,

Has anyone checked the implementation of the MMFF94 force field in both
Sybyl and Cerius2?

My concern follows some contrasting results observed when a client and
myself both modelled the same compound in the cis and trans forms (about a
butadiene moiety in the structure).  The difference in conformational
energies obtained from the two packages was staggering!

Although both companies claim to have incorporated the force field into
their MM engines, they do not produce comparable results; both in terms of
energy differences and of the predicted lowest energy conformation.

One test I ran on Sybyl came from the Gundertofte MM comparison paper
(Gundertofte K, et al, J. Comp. Chem., vol.17, no.4, 429-449 (1996)) and
looked at the cis and trans forms of butadiene.  The energy difference
between these two forms agreed with the literature result within 0.1 kcal.
I'm awaiting the clients test on the same system.

If anyone has **independently** examined the force field in these packages,
I'd be very keen to hear if the results were comparable.

Many thanks

Adrian.