Deciphering the scaling of single-molecule interactions using Jarzynski’s equality

• Published in: Nature communications Vol. 5; no. 1; p. 5539
• Main Authors: Raman, Sangeetha, Utzig, Thomas, Baimpos, Theodoros, Ratna Shrestha, Buddha, Valtiner, Markus
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.11.2014; Nature Publishing Group
• Subjects: 142/136; 639/301/119; 639/638/440/951; Acids - metabolism; Amines - metabolism; Cell Adhesion - physiology; Cell Communication; Cell Membrane - physiology; Energy Transfer; Humanities and Social Sciences; Lipid Bilayers - metabolism; Microscopy, Atomic Force; multidisciplinary; Nanotechnology; Science; Science (multidisciplinary); Spectrophotometry, Atomic; Thermodynamics
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms6539

Unravelling the complexity of the macroscopic world relies on understanding the scaling of single-molecule interactions towards integral macroscopic interactions. Here, we demonstrate the scaling of single acid–amine interactions through a synergistic experimental approach combining macroscopic surface forces apparatus experiments and single-molecule force spectroscopy. This experimental framework is ideal for testing the well-renowned Jarzynski’s equality, which relates work performed under non-equilibrium conditions with equilibrium free energy. Macroscopic equilibrium measurements scale linearly with the number density of interfacial bonds, providing acid–amine interaction energies of 10.9±0.2 kT. Irrespective of how far from equilibrium single-molecule experiments are performed, the Jarzynski’s free energy converges to 11±1 kT. Our results validate the applicability of Jarzynski’s equality to unravel the scaling of non-equilibrium single-molecule experiments to scenarios where large numbers of molecules interacts simultaneously in equilibrium. The developed scaling strategy predicts large-scale properties such as adhesion or cell–cell interactions on the basis of single-molecule measurements. Adhesion forces depend on the strength and density of the individual molecular interactions of which they are composed. Here, the authors use surface force apparatus and atomic force microscopy to experimentally probe the scaling of single-molecule interactions into macroscopic properties.