CHASM (Chain Alignment on the Surface of Materials): An Algorithm for Predicting Polymer and Polypeptide Conformations at Interfaces

Herein, we describe a lattice-matching algorithm, adopted from the unimodular matrix coincident-site lattice approach, that can be used for determining the low-energy orientation(s) for a macromolecular chain (polymer, polypeptide) that adsorbs directly onto a well-defined periodic surface, such as an exposed inorganic crystal surface or an oriented organic film. The program, CHASM (for chain alignment on the surface of materials), utilizes transformation ( S ), rotation ( R ), and deformation ( D ) matrix operations to generate angular-dependent lattice overlap patterns for the two components. From the coincidence pattern generated from lattice overlap at a given angle of rotation, CHASM determines either the periodicity ( N‘ ) or a dislocation energy parameter ( P ), both of which are measurements of the stability of a given interface. In this report, we benchmark the CHASM algorithm against STM and X-ray diffraction data obtained for oriented polyethers, polyamides, poly(caprolactone), and lysozyme adsorbed onto periodic substrates. We find that the CHASM-predicted orientations exhibit excellent agreement with experimental data.