Spectroscopic Probing of the Microenvironment in a Protein−Surfactant Assembly

Abstract

The effect of the anionic surfactant sodium dodecyl sulfate (SDS) on the protein human serum albumin (HSA) was studied using steady-state spectroscopy, time-resolved measurements, and circular dichroism spectroscopy. The binding of SDS to the domain IIA of HSA, housing the single tryptophan amino acid residue (Trp214), was monitored, and it was found that this addition of the surfactant takes place in a sequential manner depending upon the concentration of the added surfactant. Both fluorescence intensity and lifetimes of HSA decreased with the increasing concentration of SDS, and the surfactant molecules serve the role of a quencher for the fluorescence of Trp214. Circular dichroism data also support the structural changes induced by SDS. The 17 disulfide bridges present in HSA provide the necessary structural rigidity to the protein. Stern-Volmer plots and thermodynamic parameters have been used to characterize the sequential binding of SDS to HSA, and these parameters not only confirm that the binding is spontaneous in nature but also is quite strong, depending on the concentration of the added surfactant.

Comprehensive exploration of the anticancer activities of procaine and its binding with calf thymus DNA: a multi spectroscopic and molecular modelling study

“…26,27 When quenching of uo-rophore occurs by a quencher the mechanism is either static or dynamic. Static quenching leads to the formation of the ground state complex formation while dynamic quenching comprises of the collision between the uorophore and the quencher.…”

Calorimetric and spectroscopic binding studies of amoxicillin with human serum albumin

“…where k q is the bimolecular rate constant of the quenching reaction and s 0 is the average integral fluorescence lifetime of Trp which is *5.78 9 10 -9 s [18]. The binding constant (K b ) and the binding stoichiometry (n) can be calculated using the following equation [19,20] log…”

Quenching interaction of BSA with DTAB is dynamic in nature: A spectroscopic insight

“…From the magnitudes of the relative contributions of lifetimes a 1 and a 2 (Table 1), it may be suggested that for the native BSA (in the absence of DTAB), the contribution from faster lifetime is around 15% whereas that from the slower lifetime is around 85% [6,28,29]. During the process of quenching, interactions of the quencher molecules with the substrate lead to the distortion of the indole ring planarity thereby changing the local environment around the Trp residue causing a decrement in the lifetime [28,29].…”

“…However, protein misfolding results in serious consequences leading to diseases like Alzheimer's, Parkinson's and cancer [3]. The topic of unfolding/denaturation, i.e., the structural changes of proteins brought in by chemical denaturants such as surfactants, drugs, salts, and also by physical denaturants like changes in temperature and pH has been well documented [4][5][6][7][8][9][10][11][12].…”

“…The interaction between proteins and surfactants has been extensively studied, with the aim of understanding the action of surfactants as denaturants and solubilizing agents for membranes of proteins and lipids [4][5][6][18][19][20][21][22]. The specific and nonspecific interactions of proteins with surfactants are of fundamental importance both from the principle understanding and application viewpoints.…”