Quantitative structure-polarization relationships (QSPR) study of BTEX tracers for the formation of antibody-BTEX-EDF complex.

The multiple linear regression (MLR) analysis and back propagation neural networks (NN) were performed to examine the quantitative structure-polarization relationships (QSPR) for the formation of antibody-BTEX-EDF complex. Five descriptors out of 18 ones were selected for both MLR and NN, respectively, and the selected descriptors in MLR were the same as those in NN. These descriptors were the number of atoms, which can form hydrogen bonds (HA), connolly surface area (Area), the highest occupied molecular orbital energy (HOMO), partial charge of C3 carbon atom (C3), and HOMO pi coefficient of C2 carbon atom (P2). The fact that the descriptors in MLR are identical to those in NN suggests that these descriptors have good linear relationships and play a significant role in the formation of antibody-tracer complex.

An investigation of phosphopeptide binding to SH2 domain.

A comparative molecular field analysis (CoMFA) was carried out to investigate quantitative structure-activity relationships for SH2-binding phosphopeptides. Two alignment rules were applied in our CoMFA model. The phosphopeptide backbone atoms were used for superposition in alignment I and the backbone atoms of peptide-binding residues of SH2-phosphopeptide complexes were used in alignment II to consider the position of phosphopeptides in SH2-binding sites. The higher correlation and predictivity in alignment II (r(2) value of 0.961 and cross-validated r(2) value of 0.682) suggest that the consideration of peptide-binding position at the binding sites gives rise to better results when the ligand-receptor complex structure is considered. In addition, CoMFA contour and electrostatic maps were well accorded with the experimental results in which the replacement of N-terminal residues with an acetyl group reduced the binding affinity. Therefore, the modification of molecular size and charge of phosphopeptides can be carried out based on these contour maps in order to increase binding affinities.