Fluorescence Lifetime Probe for Solvent Microviscosity Utilizing Anilinonaphthalene Sulfonate

Abstract

The correlation between the fluorescent dynamics of excited anilinonaphthalene sulfonate (ANS) and the microviscosity of solvent molecules surrounding ANS is investigated by time-resolved fluorescence spectroscopy. ANS has been widely used to probe the local hydrophobicity due to the drastic change in its intensity. It is revealed that the fluorescence lifetime from the charge transfer (CT) state of ANS sensitively reflects the microviscosity. The higher sensitivity of 2,6-ANS than of 1,8-ANS demonstrates that the spatial freedom of the rotating phenylamino group in the photoexcited ANS is an important factor that determines the sensitivity. As an application, the measurements of the microviscosity of water in biologically important systems, such as hyaluronan, gellan gum, and gelatin aqueous solutions are also presented. The present results suggest that the fluorescence lifetime of ANS enables the estimation of the solvent microviscosity and provide a useful probe molecule for fluorescence lifetime imaging microscopy.

Protein-Ligand Interactions and Allosteric Regulation of Activity in DREAM Protein

“…The lifetime of 1,8-ANS in 20 mM Tris pH 7.4 was measured to be 0.27 ns with a minor fraction (~ 2%) of a 4 ns lifetime due to the non-planar excited state decay (Upadhyay et al 1995, Someya, Yui 2010. The lifetime of 2.6-ANS was determined to be 0.35 ns in agreement with a previously determined value (León et al 2009).…”

Temperature and Phase Transition Sensing in Liquids with Fluorescent Probes

“…The lifetime-based techniques generally require more complex diagnostic equipment compared to intensity-based measurements, though they are less sensitive to environmental effects. Besides the temperature measurements, the fluorescent techniques also were employed in studies of flows inside micro channels in lab-on-chip applications [9,10], in microviscosity investigations [11,12], air flow sensing [13,14], and as pressure measurements [15]. In order to achieve stable and reliable results, the certain balance between isolation and overlap of the probe with the environment is desired.…”

Microviscosity of Supercooled Water Confined within Aminopropyl-modified Mesoporous Silica as Studied by Time-resolved Fluorescence Spectroscopy

“…For that purpose, mesoporous silica with a dense aminopropyl (AP) layer (2.1 molecules nm -2 ) was prepared by post grafting of APTES to the pore surface of surfactant-templated mesoporous silica (diameter of the silica framework, 3.1 nm), and rhodamine B (RhB) isothiocyanate was covalently bound to part of the surface AP groups. Time-resolved fluorescence properties of fluorescent dyes have been used to study the microscopic viscosity of solvents; 28,29 the estimation of microviscosity can be done by measuring fluorescence lifetime 28 or rotational diffusion time of a fluorescent dye. 29 Although the measurement of rotational diffusion time is limited to an optically transparent system without scattering of polarized light, the fluorescence lifetime measurement is applicable to a light-scattering medium.…”