title: 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.
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, 2A and 2B, Raja Subodh Chandra Mullick Rd, Jadavpur, Kolkata, West Bengal, 700032, India.
authors.forename: Shirsendu
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Physical Chemistry, Indian Association for the Cultivation of Science, 2A and 2B, Raja Subodh Chandra Mullick Rd, Jadavpur, Kolkata, West Bengal, 700032, India.
authors.forename: Kankan
authors.initials: K
authors.lastname: Bhattacharyya
mesh_terms: D000906:Antibodies / Q000737:chemistry; D004058:Diffusion; D049452:Green Fluorescent Proteins / Q000737:chemistry; D006801:Humans; D020100:Hydrogels; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008823:Micelles; D011487:Protein Conformation; D012709:Serum Albumin / Q000737:chemistry; D000072760:Single Molecule Imaging / Q000379:methods*; D013501:Surface-Active Agents / Q000737:chemistry; D044366:Transition Temperature; D014404:Tubulin / Q000737:chemistry; D014783:Viscosity
chemical_list: D000906:Antibodies; D020100:Hydrogels; D052578:Ionic Liquids; D008051:Lipid Bilayers; D008081:Liposomes; D008823:Micelles; D012709:Serum Albumin; D013501:Surface-Active Agents; D014404:Tubulin; D049452:Green Fluorescent Proteins
keywords: binary mixture; conformational fluctuation of proteins; heterogeneity; ionic liquids; single-molecule studies