Models organ system approach

Combined quantum/classical treatment of molecular systems was introduced first in the pioneering paper of Warshel and Levitt. This paper contains the main features of the QM/MM approach widely used (with modifications) in other works on modeling organic systems. The authors considered a relatively large biological enzyme-substrate complex to study the mechanism of the lysozyme reaction of cleavage of hexasacharides with particular emphasis on factors that contribute to the stabilization of the carbonium ion intermediate. 

Since current quality system models employ a systems approach, an audit checklist that is organized by subsystem may be helpful, as described in Table 5. The form would include appropriate document control information such as form... 

The main advantages of MM force field models are that the terms in the potential energy representation correlate with the usual chemical intuition and that such models can easily be combined with force fields for modeling organic molecules. The latter permits the use of a consistent approach for calculation of sorbate-zeolite systems. A drawback is that a large number of parameters must be determined on the basis of either experimental information or quantum chemical calculations (or by a combination of both). 

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