title: Torsion profiling of proteins using magnetic particles.
abstract: We report a method to profile the torsional spring properties of proteins as a function of the angle of rotation. The torque is applied by superparamagnetic particles and has been calibrated while taking account of the magnetization dynamics of the particles. We record and compare the torsional profiles of single Protein G-Immunoglobulin G (IgG) and IgG-IgG complexes, sandwiched between a substrate and a superparamagnetic particle, for torques in the range between 0.5 × 10(3) and 5 × 10(3) pN·nm. Both molecular systems show torsional stiffening for increasing rotation angle, but the elastic and inelastic torsion stiffnesses are remarkably different. We interpret the results in terms of the structural properties of the molecules. The torsion profiling technique opens new dimensions for research on biomolecular characterization and for research on bio-nanomechanical structure-function relationships.
authors.affiliation: Eindhoven University of Technology, Eindhoven, The Netherlands. a.v.reenen@tue.nl
authors.forename: A
authors.initials: A
authors.lastname: van Reenen
authors.forename: F
authors.initials: F
authors.lastname: Gutiérrez-Mejía
authors.forename: L J
authors.initials: LJ
authors.lastname: van Ĳzendoorn
authors.forename: M W J
authors.initials: MW
authors.lastname: Prins
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D004548:Elasticity; D007074:Immunoglobulin G / Q000737:chemistry*; D058185:Magnetite Nanoparticles; D055503:Protein Multimerization; D012399:Rotation; D019415:Torque
chemical_list: D001426:Bacterial Proteins; C034284:IgG Fc-binding protein, Streptococcus; D007074:Immunoglobulin G; D058185:Magnetite Nanoparticles