In Eq. ( ), chiral molecules have contributions in the translation-rotation (Ξ tr ) and rotationtranslation (Ξ rt ) coupling tensor. Normally, these tensors depend on the origin of the coordinate system, but at the center of resistance, they both become symmetric. For chiral molecules, the eigenvalues of Ξ tr have the same magnitudes, but flip signs for the two mirror images. Using rotational invariants for both Ξ tr and Ξ tt , we have developed the molecular equivalent of the pitch for a screw or propeller travelling through a medium,