I have a .pqr file generated using the APBS website and I want to calculate the electrostatic potential for each atom of the proteins using this. I did this using the surface analysis --> Coulombic Surface on Chimera. As part of my current research I am supposed to write a code on python for the same but when I compare the results, I am getting different results. Can someone please explain how to calculate the atom electrostatic potentials from a .pqr file theoretically?

Thanks,

Arth