Optical tweezers in single-molecule experiments
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Optical tweezers in single-molecule experiments Annamaria Zaltrona , Michele Merano, Giampaolo Mistura, Cinzia Sada, Flavio Seno Physics and Astronomy Department, University of Padua, via Marzolo 8, 35131 Padova, Italy Received: 17 June 2020 / Accepted: 31 October 2020 © The Author(s) 2020
Abstract In the last decades, optical tweezers have progressively emerged as a unique tool to investigate the biophysical world, allowing to manipulate and control forces and movements of one molecule at a time with unprecedented resolution. In this review, we present the use of optical tweezers to perform single-molecule force spectroscopy investigations from an experimental perspective. After a comparison with other single-molecule force spectroscopy techniques, we illustrate at an introductory level the physical principles underlying optical trapping and the main experimental configurations employed nowadays in single-molecule experiments. We conclude with a brief summary of some remarkable results achieved with this approach in different biological systems, with the aim to highlight the great variety of experimental possibilities offered by optical tweezers to scientists interested in this research field.
1 Introduction Since ancient times, humans have being fascinated by light, which is intimately involved with our existence and strongly affects our daily lives. Already in the Ancient Greece, mathematicians and philosophers were interested in light phenomena, just think of Euclid, who summarized the knowledge at his time on light reflection and refraction in his work Optica, where he proposed for the first time mathematical formulas to describe such effects. For a long time, the studies on light were strictly connected to astronomy and it was only in the 17–18th centuries that scientists began wondering about the physical nature of light. The understanding that light is a form of electromagnetic wave marked a turning point in physics and opened the way to a new driving force in scientific investigations: the creation and control of light at will and the possibility to exploit it to make progress also in research fields other than physics. The potentiality of using light to probe the structure of matter has been then boosted by the discovery of photons. In this scenario, surely the invention of optical tweezers more than three decades ago represents a milestone. The first optical trapping of microscopic particles was reported in 1970 by Arthur Ashkin [1–3] at Bell Laboratories, who was awarded by the Nobel prize in 2018 for this discovery. Although the underlying physical principle of Optical Tweezers (OT), the so-called radiation pressure, was known since long time, only thanks to the technological developments achieved in the ’60s, it was possible to overcome the limitations that seemed to make unfeasible till then any practical use of this manipulation method. Ashkin’s work pioneered the field of opti-
a e-mail: [email protected] (corresponding author)
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