Single-molecule Spectroscopy: Exploring Heterogeneity in Chemical and Biological Systems

Abstract

Many chemical and biological systems are heterogeneous in the molecular length scale (∼ 1 nm). Heterogeneity in many chemical systems and organized assemblies may be monitored using single-molecule spectroscopy (SMS). In SMS, the size of the focal spot (i.e., the smallest region to be probed) is nearly half of the excitation wavelength (λ/2, i.e., 200-375 nm) for visible light (400-750 nm). We discuss how one can get spatial resolutions better than 200 nm using molecules as nanometric probes. We show that polymer hydrogels, lipid vesicles, room temperature ionic liquids (RTILs), and binary liquid mixtures exhibit such heterogeneity. Another important observation is solute-dependent friction in RTILs. In an RTIL, diffusion of an ionic solute is slower than that of a neutral solute.

Room-Temperature Ionic Liquids and Biomembranes: Setting the Stage for Applications in Pharmacology, Biomedicine, and Bionanotechnology

“…The broad interdisciplinary character of the subject makes it relevant a panoply of other methods often borrowed from biology, which in several cases provide structural information and sometimes measure dynamic properties. Examples are fluorescence correlation spectroscopy (FCS), , fluorescence resonance energy transfer (FRET), surface plasmon resonance, confocal scanning microscopy, scanning electron microscopy, and NMR.…”

Single-molecule fluorescence resonance energy transfer in molecular biology

“…47 Protein conformational dynamics smFRET assays have been widely used to determine complex conformational heterogeneity and structural dynamics of proteins in vivo and in vitro. [71][72][73][74][75][76][77][78][79][80] Here, T4 lysozyme is used as an example to illustrate the conformational dynamics of proteins. T4 lysozyme is an enzyme composed of two domains connected by an α-helix (Fig.…”

Two-Dimensional Fluctuation Correlation Spectroscopy (2D-FlucCS): A Method to Determine the Origin of Relaxation Rate Dispersion

“…32 sm-FRET has also been demonstrated to be capable of detecting the presence of heterogeneity in a variety of systems, such as conformational fluctuations in proteins, 21 immiscible binary mixtures, etc. 33 Integrating the capabilities of 2D-FLCS with sm-FRET, a comprehensive insight into the conformational dynamics and ligand binding mechanisms of the Bsu preQ 1 aptamer and its energy landscape was unveiled on a microsecond time scale. This synergistic approach provided a detailed understanding of the gene regulation process occurring in bacteria.…”