title: Spectroscopic studies of catanionic reverse microemulsion: correlation with the superactivity of horseradish peroxidase enzyme in a restricted environment.
abstract: Catanionic microemulsions formed by dodecyltrimethylammonium bromide (DTAB), sodium dodecyl sulfate (SDS), n-hexanol, dodecane, and citrate buffer have been characterized by using dynamic light scattering (DLS) and spectroscopic studies. While the DLS measurements provide information about the hydrodynamic diameters of the microemulsion droplets formed upon variation of the constituents, steady-state and time-resolved fluorescence emission experiments probe the polarity and the dynamics of the trapped solvent pool inside of the microemulsion droplets of nanometer dimension. In addition, time-resolved fluorescence anisotropy shows the rigidity of the confined solvent pool as well as the coupling between the motion of a solute and those of the solvent molecules. The results obtained from the DLS and those from the steady-state and time-resolved fluorescence emission studies have been found to correlate well with the superactivity of horseradish peroxidase enzyme in the catanionic microemulsions. Subsequently, the time-zero estimate for the dynamic Stokes shift in these microemulsions reveals that approximately 50% of the total solvent dynamical response is missed due to the limited time resolution employed in our experiments. The amplitude of the missing portion is similar to what has been observed recently for nanoscopic water by Fayer and co-workers (Piletic, I. R.; Tan, H.-S.; Fayer, M. D. J. Phys. Chem. B 2005, 109, 21273).
authors.affiliation: Department of Chemical, Biological and Macromolecular Sciences, and Unit for Nanoscience and Technology, S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700 098, India. ranjit@bose.res.in
authors.forename: Ranjit
authors.initials: R
authors.lastname: Biswas
authors.forename: Arup R
authors.initials: AR
authors.lastname: Das
authors.forename: Tuhin
authors.initials: T
authors.lastname: Pradhan
authors.forename: Didier
authors.initials: D
authors.lastname: Touraud
authors.forename: Werner
authors.initials: W
authors.lastname: Kunz
authors.forename: Sekh
authors.initials: S
authors.lastname: Mahiuddin
mesh_terms: D000838:Anions; D002021:Buffers; D002412:Cations; D004655:Emulsions; D006735:Horseradish Peroxidase / Q000378:metabolism*; D012995:Solubility; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000838:Anions; D002021:Buffers; D002412:Cations; D004655:Emulsions; D006735:Horseradish Peroxidase