TweeTERS · Coupling of Optical tweezers with Tip-enhanced Raman Spectroscopy for single-molecule investigation of supramolecular systems

Coupling of Optical tweezers with Tip-enhanced Raman Spectroscopy for single-molecule investigation of supramolecular systems

Synthetic supramolecular systems consist of an ensemble of molecules held together by non-covalent interactions. Among such forces, hydrogen bonds are particularly relevant in fundamental biological and chemical processes. From the fundamental point of view, understanding non-covalent interactions is paramount to disentangle the chemistry of biological systems. One of the main challenges in the field nowadays is the investigation of single-molecule events under non-equilibrium conditions. To this end, optical trapping (OT) experiments have been successfully implemented to determine the mechanical properties and operational dynamics of synthetic supramolecular systems in the single-molecule regime and under aqueous environments. This is achieved by exerting calibrated forces on systems immobilized between optically trapped particles and measuring the corresponding displacements in real time. For example, characteristic H-bond strength have been determined in situ for single host-guest pairs as well as real-time shuttling of molecular shuttles using optical trapping. Despite the essential information that optical force microscopy experiments provide, there is still a lack of quantitative chemical information. Raman spectroscopy is one of the most powerful tools in analytical chemistry since it can access the vibrational spectrum of samples in a non-invasive way, from which the specific composition of a sample, its conformation and interaction between species can be determined. Consequently, Raman is an ideal tool to provide complementary chemical characterization in OT experiments, particularly in biologically relevant aqueous environments. However, due to the small scattering cross-sections of the Raman process, nearfield approaches using metallic nanoantennas have to be used to access the Raman spectrum of a single molecule. In tip-enhanced Raman spectroscopy (TERS) the excitation light is coupled to the apex of nanometric metallic tip, resulting in a highly enhanced and confined nearfield around the tip apex. The Raman signal from molecules within the nearfield is enhanced by several orders of magnitude with respect to the farfield signal, boosting the sensitivity of the process to the single-molecule limit. By combining state-of-the-art technologies in the fields of OT and nearfield Raman spectroscopy, the main objective of TweeTERS is to create a hybrid tool that can disentangle the relation between mechanical, conformational and chemical properties of individual synthetic supramolecular systems and the non-covalent interactions governing their behavior, with single-molecule sensitivity and spatial resolution in the range of 5-10nm. On the one hand, we will be able to follow in real-time the formation and breaking of individual non-covalent interactions both kinetically and chemically tackling open questions in the field of supramolecular chemistry from a completely new approach. On the other hand, this unique novel instrument will merge two state-of-art single molecule techniques, resulting in a versatile setup with applicability far beyond a single research field and topic pushing the limits of current technology in the single molecule regime.

Текст от CORDIS, на английски · Данни: CORDIS, © Европейски съюз