Intramolecular Charge Transfer as Probing Reaction:  Fluorescence Monitoring of Protein−Surfactant Interaction

Abstract

Ethyl p-(dimethylamino)cinnamate (EDAC) has been used as a fluorescence probe for monitoring the interaction between a model water-soluble protein, bovine serum albumin (BSA), and an anionic surfactant, sodium dodecyl sulfate (SDS). The probe EDAC undergoes intramolecular charge transfer (ICT) in the excited state in water and other polar solvents. The emission from the ICT state becomes more intense and blue-shifted due to reduced polarity in the hydrophobic environments of BSA and SDS micelles relative to that in pure water. The intensity of the ICT emission from EDAC increases with surfactant concentration and reaches a maximum at the critical micelle concentration of SDS, which can be employed as a simple technique for following micellization. Analysis of the fluorescence spectra of the probe provide evidences in favor of surfactant-induced protein uncoiling due to massive binding of the SDS molecules to BSA in the cooperative binding region of the binding curve, describing protein (BSA)−surfactant (SDS) interaction. The polarity of the BSA−SDS aggregate formed is intermediate between that of hydrophobic regions of BSA and SDS micelles as sensed by the intramolecular charge-transfer (ICT) probe, EDAC.

Spectroscopic study of excited state intramolecular charge transfer in ethyl ester of N,N′-Dimethylaminonaphthyl-(acrylic)-acid

“…For the same excitation, in polar solvents such as acetonitrile and water, dual fluorescence is observedone higher energy band at $425 nm and another lower energy band which ranges between 465 nm in chloroform solvent to 521 nm in water. Comparing with similar types of studied systems [8][9][10][11][12]33,35,50] the higher energy band with weaker intensity is assigned to the emission from the LE state and the lower energy strong emission band is assigned to the emission from the CT state. This assign- ment of CT emission is based on the polarity dependency of the position of emission maxima of the red shifted band [8][9][10][11][12].…”

Chemically Induced Unfolding of Bovine Serum Albumin by Urea and Sodium Dodecyl Sulfate: A Spectral Study with the Polarity‐Sensitive Charge‐Transfer Fluorescent Probe (E)‐3‐(4‐Methylaminophenyl)acrylic Acid Methyl Ester

“…The leveling off of the anisotropy above about 70 mm BSA is consistent with other reported similar cases. [2][3][4] …”

A fluorescence study of differently substituted 3‐styrylindoles and their interaction with bovine serum albumin

“…(7), and 5-methoxy-3-[2-(4-chlorophenyl)ethenyl-E ]-NH-indole (8). This is because the absorption and fluorescence properties of 3-(2-phenylethenyl- (6) in organic solvents have already been reported (16). However, the absorption and fluorescence properties of all eight compounds (1-8) have been examined in BSA and are reported herein.…”

“…All the solutions were prepared and handled under dim light conditions. (6) were prepared as reported earlier (15,16). (8) were prepared by the condensation of either 5-bromoindole-3-carboxaldehyde or 5-methoxyindole-3-carboxaldehyde with p-nitrophenylacetic acid or p-chlorophenylacetic acid in the presence of piperidine in pyridine at 90°C (15).…”

“…Several types of push-pull molecular systems capable of forming intramolecular charge transfer (ICT) fluorescent excited states serve as extrinsic fluorescence probes (2,5,6). Diphenylpolyenes capable of fluorescing from their charge transfer excited states have been considered as useful and further employed to study the microenvironment of micelles and proteins (7)(8)(9)(10)(11)(12)(13)(14).…”