Structural Transformation of Bovine Serum Albumin Induced by Dimethyl Sulfoxide and Probed by Fluorescence Correlation Spectroscopy and Additional Methods

Abstract

Determining the structure of a protein and its transformation under different conditions is key to understanding its activity. The structural stability and activity of proteins in aqueous-organic solvent mixtures, which is an intriguing topic of research in biochemistry, is dependent on the nature of the protein and the properties of the medium. Herein, the effect of a commonly used cosolvent, dimethyl sulfoxide (DMSO), on the structure and conformational dynamics of bovine serum albumin (BSA) protein is studied by fluorescence correlation spectroscopy (FCS) measurements on fluorescein isothiocyanate (FITC)-labeled BSA. The FCS study reveals a change of the hydrodynamic radius of BSA from 3.7 nm in the native state to 7.0 nm in the presence of 40% DMSO, which suggests complete unfolding of the protein under these conditions. Fluorescence self-quenching of FITC has been exploited to understand the conformational dynamics of BSA. The time constant of the conformational dynamics of BSA is found to change from 35 μs in its native state to 50 μs as the protein unfolds with increasing DMSO concentration. The FCS results are corroborated by the near-UV circular dichroism spectra of the protein, which suggest a loss of its tertiary structure with increasing concentration of DMSO. The intrinsic fluorescence of BSA and the fluorescence response of 1-anilinonaphthalene-8-sulfonic acid, used as a probe molecule, provide information that is consistent with the FCS measurements, except that aggregation of BSA is observed in the presence of 40% DMSO in the ensemble measurements.

Tracking structural transitions of bovine serum albumin in surfactant solutions by fluorescence correlation spectroscopy and fluorescence lifetime analysis

“…18 In our experiment, we did not observe such a phenomenon because of the extremely low concentration of BSA in surfactant solutions. However, it happens only when the protein concentration is high enough.…”

“…4,12,13 However, at present we still do not completely understand how the structure of a protein changes quantitatively in different charged surfactant solutions on the basis of the classical "necklace-bead" model. 18 The FCS technique was further developed for such studies. 14 Fluorescence correlation spectroscopy (FCS) captures these subtle dynamical changes at a single-protein level in terms of the diffusion coefficient.…”

Anti-cancerous effect of albumin coated silver nanoparticles on MDA-MB 231 human breast cancer cell line

“…In the near-UV region, the typical CD signals of BSA 32 were found to be almost conserved for both ASNPs and ANPs (Fig. 5B).…”

Nonmonotonic Hydration Behavior of Bovine Serum Albumin in Alcohol/Water Binary Mixtures: A Terahertz Spectroscopic Investigation

“…[26,27] It has been known for al ongt ime that low concentrations of alcohols stabilize proteins as ar esult of preferentials olvation of the alcohol molecules at the protein surface, [28] and the addition of alcohol induces a-helix formation in ac ertainc lass of proteins, [29][30][31] for which the effect is dependent on the length of the carbon chain of the alcohol. [38][39][40] In ar ecent study, [38] the effect of ethanolo nB SA was found to be bimodal;t he abundance of the secondary structural content was found to be dependent on the concentration of ethanol, which contrasts the findings of other proteins such as lysozyme [34] and melittin. At high alcohol concentrations, the We report the experimentalo bservation of nonmonotonic changes in the collective hydration of bovines erum albumin (BSA) in the presence of alcohols of varying carbon-chain lengths, that is, ethanol, 2-propanol, and tert-butyl alcohol (TBA), by using terahertz (THz) time domain spectroscopy.…”