bool OEReceptorSetProteinConstraint(OEChem::OEMolBase& receptor,
                                    OEProteinConstraint& proteinConstraint)

Sets a protein constraint. If the receptor already has a constraint on OEProteinConstraint::GetAtom the constraint will be replaced, otherwise a new one will be created.

Returns true if successful.

It is only valid to call this function if receptor is a valid receptor (i.e., OEIsReceptor returns true).