On the interaction of Bovine Serum Albumin (BSA) with cethyltrimethyl ammonium chloride surfactant: Electron Paramagnetic Resonance (EPR) study

Abstract

Electron paramagnetic resonance (EPR) has been used to monitor the interaction of bovine serum albumin (BSA) with cationic cethyltrimethylammonium chloride (CTAC) at pH 7.0. EPR results using 5-DSA and 16-DSA nitroxide spin labels show that in the presence of BSA the EPR spectra are composed of two label populations, one contacting the protein and a second one due to label localization in the micelles. Evidence is also obtained for a competition of the surfactants with the spin labels for the high affinity binding sites of the stearic acid spin labels as monitored by changes in the fraction of the two label populations as the surfactant concentration is increased. The effect of sodium dodecylsulfate (SDS) reported previously seems to be stronger in the sense that increase in SDS concentration leads to a complete transfer of spin label from close protein contact sites to the micelles while for CTAC, apparently, a significant immobilization of probe remains even at higher surfactant concentrations. EPR gives information on the dynamics inside the protein-surfactant aggregates and associated to label localization and motion. The dynamics of the nitroxide spin-labels bound to the protein correlate to the stronger binding of SDS to BSA as compared to CTAC binding. Simulation of EPR spectra for spin labels in pure CTAC micelles, in pure protein or in protein-bound micelles show rotational correlation times similar to those obtained from the simple evaluation based on the intensities of nitrogen hyperfine coupling components. Rotational correlation times obtained for 5-DSA bound to protein are larger as compared to 16-DSA values suggesting greater mobility for the later even when bound to the protein.

Interaction of Miltefosine with the Lipid and Protein Components of the Erythrocyte Membrane

“…The spin label 5‐MSL covalently bound to the single free thiol group of BSA showed that, in the presence of surfactants, increases occur in backbone dynamics and the protein assumes more expanded conformations, which increase the exposure to the solvent 35. Several models have emerged to describe the structure of the detergent–protein complexes involved in protein denaturation, with the “pearl necklace” model being the most discussed in the literature 43,44. In this model, surfactant aggregates wrap around the hydrophobic polypeptide chains and form micelle‐like structures 43.…”

Measuring rotational diffusion of macromolecules by fluorescence correlation spectroscopy

“…where |l,m is an eigenfunction of the angular momentum operator obeying the two relations (11) Inserting eqn (10) into eqn (8) yields (13) Next, one has to clarify how the rotation operator R acts on |l,m . One of the most lucid derivations of this action is given by Feynman in ref.…”

“…BSA is the most studied example of a serum albumin, which has attracted considerable attention over the past decades (see ref. 10 and references therein). The other two proteins studied here are aldolase from rabbit muscles, and hen egg ovalbumin.…”

Identification of free radicals induced by gamma irradiation in amino acid derivatives

“…The electron paramagnetic resonance (EPR) has been widely used for the identification of irradiation damage centers in many substances including amino acid and their derivatives [5][6][7][8][9][10][11][12][13][14][15]. In previous study, Almanov et.al.…”