optical tweezers, our nanometer-size fingers to touch the world of molecules and cells

Force has a fundamental role in biological processes. all biological motion, from cellular motility to replication and segregation of dna, is driven by molecular-scale forces. conversely, the elimination or reduction of motions by various methods, such as binding ligands to their cognate receptors or through folding a protein that creates a stable three-dimensional structure, involves the formation of bonds that overcome these forces. the ability to study these fundamental processes has been evolved over the past 20 years by the development of techniques that make it possible to measure the force and displacement generated by single molecules and cells. so far, a range of single-molecule manipulation techniques, including optical tweezers (ot), magnetic tweezers (mt), atomic force microscopy (afm), microneedle manipulation, and flow-induced stretching, have been expanded significantly. among them, ot a technology which is recognized by 2018 physics nobel prize, has revolutionized the way we understand molecular processes. the ability to record and apply piconotonic range forces along with the measurement of nanometer displacements has enabled us to use this state-of-the-art technology to record molecular motions and understand the mechanism of action of some very complex biological systems. over the past decade, studies of optical tweezers have clarified the function of chaperones, motor proteins, and molecular defence systems that prevent the formation of toxic accumulations in cells. also, with this method, some innovative studies have been done to determine the 3d structure of proteins. in this presentation. we begin with an overview highlighting areas of investigation opened up by the ability to apply force and to measure displacement at the single-molecule level. then we describe the operating principles and practical implementation of optical tweezers. many excellent reviews and detailed technical reports on the design, fabrication and use of these instruments are available.