ABSTRACT
Most commonly, cells have been considered so far as small vessels that contain a complex mixture of chemical species undergoing reactions through diffusion and random collision. On the other hand, cell processes, such as chromosomal segregation, translocation of organelles from one part of the cell to another, protein import into organelles, or the maintenance of a voltage across the membrane, involve directional movements and transport of chemical species, in some cases against electrochemical gradients. Processes like replication, transcription, and translation require directional information
6.1 Introduction .................................................................................................. 165 6.2 Effect of Force on Thermodynamics and Kinetics of a Reaction ................ 166
6.2.1 Effect of Force on the Free Energy of a Reaction ............................ 167 6.2.2 Effect of Force on the Kinetics of a Reaction................................... 170
6.3 Single-Molecule Force Spectroscopy ........................................................... 171 6.3.1 Methodologies for Single-Molecule Force Spectroscopy ................. 172 6.3.2 Mapping the Position of the Barrier according
to the Dynamic Force Spectroscopy Approach ................................ 174 6.3.3 AFM-Based Single-Molecule Force Spectroscopy
of GB1 Protein ...........................................................................175 6.3.4 AFM-Based Single-Molecule Force Spectroscopy
of GB1 Protein in the Presence of Chemical Osmolytes .................. 177 6.3.5 Molecular Engineering of Mechanical Properties ........................... 179
6.4 Mechanochemistry of a Single Covalent Bond ............................................ 185 6.4.1 Disul¡de Bond Reduction Reactions by Small Nucleophiles........... 185
6.5 Mechanochemistry for a Targeted Delivery of Single Molecules ................ 189 6.6 Conclusion and Prospective .......................................................................... 190 References .............................................................................................................. 190
carried out by complex molecular structures that perform in machine-like fashion. These structures are often complex assemblies of many proteins and contain parts with specialized functions, like that of converting chemical energy into mechanical work through conformational changes and displacements. Single-molecule techniques proved capable to drastically increase our understanding of mechanochemical process, i.e., of process in which mechanics and chemistry are intertwined. This chapter, after a general introduction on the effect of an external applied force on the thermodynamics and kinetics of a reaction, focuses on several studies carried out at the single-molecule level that resulted, particularly enlightening on the interplay taking place in the nanoscale between chemistry and mechanics in several biological and non-biological systems.
