Optical tweezers (OTs) use highly focused laser beams to manipulate objects at the micro- and nanoscale and represent a powerful tool to investigate the biological world, bridging the gap between physics and biology. This technique has been also employed in biophysics to perform force spectroscopy experiments at the single molecule level, where one molecule is manipulated at a time. The manipulation of individual molecules sheds light on energetics states and molecular mechanisms which are often inaccessible with bulk assays, due to the asynchronous and heterogeneous nature of the biological sample. Furthermore, in OTs the optical forces are used as mechanical denaturant agent to perturb in a controlled way the energetic state of the molecule, thus mimicking the cellular environment, wherein force often regulates biological processes. In this presentation, I will introduce the working principle of OTs, then focusing on their use to perform single-molecule force spectroscopy. I will also discuss the recent results on the investigation of protein folding and molecular binding mechanisms obtained in our lab by employing this optical technique.
