Drug-receptor recognition: electrostatic field lines at the receptor and dielectric effects.

1. In this paper the directional component of the vector electrostatic field emanating from a drug receptor is analysed in the three orthogonal planes. 2. B-DNA with an alternating guanine-cytosine sequence was chosen for a receptor model and the lines of force constructed for two dielectric conditions, namely the cases where firstly the dielectric is homogeneous and a constant throughout the space surrounding the receptor, and secondly where the dielectric is inhomogeneous and is treated as a vector quantity. 3. Electric field line maps indicate marked differences in the local fields situated in the helical wide and narrow grooves for the different sequences of cytosine and guanine; these variations are enhanced when the dielectric is handled as a vector. 4. The significance of electric field lines in interpreting receptor-induced ligand orientation effects is discussed since the direction of the lines is related to the torque that a receptor would impose on an attacking drug molecule.