H. Kubinyi et al., 3-DIMENSIONAL QUANTITATIVE SIMILARITY-ACTIVITY RELATIONSHIPS (3D QSIAR) FROM SEAL SIMILARITY-MATRICES, Journal of medicinal chemistry, 41(14), 1998, pp. 2553-2564
The program SEAL is suited to describe the electrostatic, steric, hydr
ophobic, and hydrogen bond donor and acceptor similarity of different
molecules in a quantitative manner. Similarity scores AF can be calcul
ated for pairs of molecules, using either a certain molecular property
or a sum of weighted properties. Alternatively, their mutual similari
ty can be derived from distances d or covariances c between SEAL-based
property fields that are calculated in a regular grid. For a set of N
chemically related molecules, such values form an N x N similarity ma
trix which can be correlated with biological activities, using either
regression analysis and an appropriate variable selection procedure or
partial least-squares (PLS) analysis. For the Cramer steroid data set
, the test set predictivities (r(pred)(2) = 0.53-0.84) of different PL
S models, based on a weighted sum of molecular properties, are superio
r to published results of CoMFA and CoMSIA studies (r(pred)(2) = 0.31-
0.40), regardless of whether a common alignment or individual, pairwis
e alignments of all molecules are used in the calculation of the simil
arity matrices. Training and test set selections have a significant in
fluence on the external predictivities of the models. Although the SEA
L similarity score between two molecules is a single number, its value
is based on the 3D properties of both molecules. The term 3D quantita
tive similarity-activity analyses (3D QSiAR) is proposed for approache
s which correlate 3D structure-derived similarity matrices with biolog
ical activities.