Bk. Alsberg et al., A new 3D molecular structure representation using quantum topology with application to structure-property relationships, CHEM INTELL, 54(2), 2000, pp. 75-91
We present a new 3D molecular structure representation based on Richard F.W
. Bader's quantum topological atoms in molecules (AIM) theory for use in qu
antitative structure-property/activity relationship (QSPR/QSAR) modeling. C
entral to this structure representation using quantum topology (StruQT) are
critical points located on the electron density distribution of the molecu
les. Other gradient fields such as the Laplacian of the electron density di
stribution can also be used. The type of critical point of particular inter
est is the bond critical point (BCP) which is here characterized by using t
he following three parameters: electron density rho, the Laplacian del rho
and the ellipticity epsilon. This representation has the advantage that the
re is no need to probe a large number of lattice points in 3D space to capt
ure the important parts of the 3D electronic structure as is necessary in,
e.g. comparative field analysis (CoMFA).
We tested the new structure representation by predicting the wavelength of
the lowest UV transition for a system of 18 anthocyanidins. Different quant
itative structure-property relationship (QSPR) models are constructed using
several chemometric/machine learning methods such as standard partial leas
t squares regression (PLS), truncated PLS variable selection, genetic algor
ithm-based variable selection and genetic programming (GP). These models id
entified bonds that either take part in decreasing or increasing the domina
nt excitation wavelength. The models also correctly emphasized on the invol
vement of the conjugated pi system for predicting the wavelength through fl
agging the BCP ellipticity parameters as important for this particular data
set. (C) 2000 Elsevier Science B.V. All rights reserved.