Solvent Dependence of the Photochemistry of the Styrylpyridinium Dye RH421

Abstract

RH421 is a widely used voltage-sensitive fluorescent membrane probe. It is also photochemically reactive and its photochemistry is dependent on its solvent surroundings. The aim of this study is to use the solvent dependence of the dye's photochemistry as an indicator of its environment within a lipid membrane. It was found that the dye actually undergoes two competing photochemical reactions. One photochemical pathway is characterized by an increase in fluorescence, the other by a fluorescence decrease. The pathway followed depends on the light intensity, the excitation wavelength and the solvent. The pathway leading to a fluorescence decrease is very dependent on the polarity of the solvent. It is promoted by solvents of high polarity (e.g., methanol, ethanol and propanol), by high intensity illumination and long wavelength excitation (i.e., 546 or 577 nm). In less polar solvents (butanol, pentanol, hexanol and heptanol) the pathway leading to a fluorescence increase dominates. The photochemical behavior observed when the dye is bound to a lipid membrane was not comparable to its behavior in any of the isotropic solvents studied. This is most likely due to the anisotropic environment of the membrane, which results in a steep gradient in polarity along the length of the dye molecule.

Interaction of Crown Ether‐Annelated Styryl Dyes with Double‐Stranded DNA

“…Nevertheless, the deviation from an ideal linear correlation indicates that other interactions with the solvent, most likely hydrogen bonding, also contribute to the stabilization or destabilization of the ground and excited state. Similar solvatochromic behavior is well-known for structurally related dyes, especially for hemicyanine dyes bearing amino-type substituents in the styryl fragment (45)(46)(47)(48)(49). No fluorescence was detected for the solutions of compound 4b at room temperature, presumably due to a very efficient non-radiative deactivation of the exitedstate.…”

Comparison between Two Anionic Reverse Micelle Interfaces: The Role of Water–Surfactant Interactions in Interfacial Properties

“…Sodium bis(2-ethylhexyl) phosphate (NaDEHP) was synthesized according ref. [60]. Both surfactants were kept under vacuum over P 2 O 5 to minimize H 2 O absorption.…”

Stopped‐Flow Fluorimetry Using Voltage‐Sensitive Fluorescent Membrane Probes

“…This conclusion was based on two findings: (i) resonance energy transfer between the dye and fluorescence probes on the enzyme and (ii) the observation of biexponential fluorescence lifetime decays of RH421 bound to na + ,K + -ATpase-containing membrane fragments. However, more extensive fluorescence studies of the dye have shown that its photochemistry is complex, and multiexponential fluorescence decays are observed even for dye in homogeneous solvents [45,[61][62][63]. Therefore, the biexponential nature of the fluorescence lifetime decays reported by Schwappach et al [60] cannot be used as evidence for direct binding to the na + ,K + -ATpase.…”