2.4. Analysis of electrostatic complementarity using the
pESP
By comparison between the pESPs of proteins A and B at the PPI
interface, the electrostatic complementarity of the two proteins in the
complex condition can be analyzed. The most important point of this
analysis is that a fully quantum mechanical EDN and ESP are used, by
which the effect of charge transfer or polarization due to complex
formation is fairly considered. Generally, quantum chemical calculations
of the EDN and ESP of a large molecule like a protein are difficult
because too much computational effort is required. By using the FMO
method, however, the computational effort can be greatly reduced.