title: Anchoring energies of liquid crystals measured on surfaces presenting oligopeptides.
abstract: We report a methodology that permits quantitation of the azimuthal anchoring energy of the nematic liquid crystal 4-cyano-4'-pentyl-biphenyl on surfaces patterned with oligopeptides. The oligopeptide (IYGEFKKKC), an optimized substrate for the Src protein kinase, was covalently immobilized via the terminal cysteine to monolayers of amine-terminated tetra(ethylene glycol) formed on gold films. The measurements of anchoring energies, which were based on a torque-balance method, revealed a systematic decrease in anchoring energy from 3.7 +/- 0.6 microJ/m2 with increasing surface density of oligopeptide. We calculate that a mass density of oligopeptide of less than 1 ng/cm2 can lead to a measurable change in the anchoring energy of the nematic liquid crystal. These results suggest that measurements of anchoring energies of liquid crystals on surfaces may offer the basis of quantitative and label-free methods for detecting biomolecules on surfaces.
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, Wisconsin 53706, USA.
authors.forename: Brian H
authors.initials: BH
authors.lastname: Clare
authors.forename: Orlando
authors.initials: O
authors.lastname: Guzman
authors.forename: Juan
authors.initials: J
authors.lastname: de Pablo
authors.forename: Nicholas L
authors.initials: NL
authors.lastname: Abbott
mesh_terms: D050866:Liquid Crystals / Q000737:chemistry*; D015394:Molecular Structure; D009842:Oligopeptides / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D009842:Oligopeptides