title: Molecular tensile machines: intrinsic acceleration of disulfide reduction by dithiothreitol.
abstract: Significant tension on the order of 1 nN is self-generated along the backbone of bottlebrush macromolecules due to steric repulsion between densely grafted side chains. The intrinsic tension is amplified upon adsorption of bottlebrush molecules onto a substrate and increases with grafting density, side chain length, and strength of adhesion to the substrate. These molecules were employed as miniature tensile machines to study the effect of mechanical force on the kinetics of disulfide reduction by dithiothreitol (DTT). For this purpose, bottlebrush macromolecules containing a disulfide linker in the middle of the backbone were synthesized by atom transfer radical polymerization (ATRP). The scission reaction was monitored through molecular imaging by atomic force microscopy (AFM). The scission rate constant increases linearly with the concentration of DTT and exponentially with mechanical tension along the disulfide bond. Moreover, the rate constant at zero force is found to be significantly lower than the reduction rate constant in bulk solution, which suggests an acidic composition of the water surface with pH = 3.7. This work demonstrates the ability of branched macromolecules to accelerate chemical reactions at specific covalent bonds without applying an external force.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
authors.forename: Yuanchao
authors.initials: Y
authors.lastname: Li
authors.forename: Alper
authors.initials: A
authors.lastname: Nese
authors.forename: Natalia V
authors.initials: NV
authors.lastname: Lebedeva
authors.forename: Tyler
authors.initials: T
authors.lastname: Davis
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Matyjaszewski
authors.forename: Sergei S
authors.initials: SS
authors.lastname: Sheiko
mesh_terms: D004220:Disulfides / Q000737:chemistry*; D004229:Dithiothreitol / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction
chemical_list: D004220:Disulfides; D004229:Dithiothreitol