1 research outputs found
Assessment of Atomic Charge Models for Gas-Phase Computations on Polypeptides
The concept of the atomic charge is extensively used
to model the
electrostatic properties of proteins. Atomic charges are not only
the basis for the electrostatic energy term in biomolecular force
fields but are also derived from quantum mechanical computations on
protein fragments to get more insight into their electronic structure.
Unfortunately there are many atomic charge schemes which lead to significantly
different results, and it is not trivial to determine which scheme
is most suitable for biomolecular studies. Therefore, we present an
extensive methodological benchmark using a selection of atomic charge
schemes [Mulliken, natural, restrained electrostatic potential, Hirshfeld-I,
electronegativity equalization method (EEM), and split-charge equilibration
(SQE)] applied to two sets of penta-alanine conformers. Our analysis
clearly shows that Hirshfeld-I charges offer the best compromise between
transferability (robustness with respect to conformational changes)
and the ability to reproduce electrostatic properties of the penta-alanine.
The benchmark also considers two charge equilibration models (EEM
and SQE), which both clearly fail to describe the locally charged
moieties in the zwitterionic form of penta-alanine. This issue is
analyzed in detail because charge equilibration models are computationally
much more attractive than the Hirshfeld-I scheme. Based on the latter
analysis, a straightforward extension of the SQE model is proposed,
SQE+Q<sup>0</sup>, that is suitable to describe biological systems
bearing many locally charged functional groups