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Chemical Fragmentation for Molecular Orbital Calculations on Proteins

Gabor Naray-Szabo ; CHINOIN Pharmaceutical and Chemical Works, H-1325 Budapest, P.O.B. 110, Hungary

Sažetak

The conceptual and mathemaitical basis of a molecular orbital
method which enables the calculation. of conformational energy
changes and other properties of proteins, is presented. The informat-·
ion inherent in the chemical formulae of the polypeptide backbone
and side chains is maximally exploited. A basis of strictly localized
molecular orbita-ls is used, thus allowing the partitioning of the
molecule into four fragments: central part (C), delocalization (D),
inductive (I) and transferable bond (T) regions. Fragment C consists
of bonds which undergo the most important chemical changes. For
this conventional self-consistent field equations with an effective
core Hamiltonian accounting for the influence of fragments D, I
a'Ild T, are given. Simple perturbation expressions are used for
fragment D in order to calculate tails of strictly localized molecular
orbitals, which account for charge transfer from and to the central
part. Only inductive effects are considered for fragment I by solving
a coupled set of 2 X 2 secul coefficients of strictly localized molecular orbit T lie very far from each other and therefore empirical strictly
transferable coefficients are used for the latter. The above procedure
allows the treating of proteins at the zero differential overlap
level, since with increasing molecular size the amount of computationa<
l work becomes proportional to the first power of the
number of bonds. Applicability of the present concept is discussed
on the basis of numerical results obtained for the electrostatic
potential and conformational properties of serine proteinases.

Ključne riječi

Hrčak ID:

194063

URI

https://hrcak.srce.hr/194063

Datum izdavanja:

14.1.1985.

Posjeta: 687 *