Representing Structural Information of Helical Charge Distributions in   Cylindrical Coordinates
  Structural information in the local electric field produced by helical charge distributions, such as dissolved DNA, is revealed in a straightforward manner employing cylindrical coordinates. Comparison of structure factors derived in terms of cylindrical and helical coordinates is made. A simple coordinate transformation serves to relate the Green function in cylindrical and helical coordinates. We also compare the electric field on the central axis of a single helix as calculated in both systems. 
David Hochberg, Thomas W. Kephart and Glenn Edwards