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A combined binding mechanism of nonionic ethoxylated surfactants to bovine serum albumin revealed by fluorescence and circular dichroism

Paper ID Volume ID Publish Year Pages File Format Full-Text
30121 44460 2015 8 PDF Available
Title
A combined binding mechanism of nonionic ethoxylated surfactants to bovine serum albumin revealed by fluorescence and circular dichroism
Abstract

•BSA is studied in interaction with C12En (n = 4,6,8) and C14EO20 respectively.•H bonding governs the interaction next to the hydrophobic attraction.•Zigzag conformation of ethyleneoxide chains (n = 4–8) allows more H bonds with BSA.•An apparent inter-conversion of the Trp rotamers occurs around the CMC of C12En.•Association constants, binding isotherms and thermodynamic parameters are given.

The study systematically investigates aqueous mixtures of fixed bovine serum albumin (BSA) and various ethoxylated nonionic surfactants belonging to a homologous series or not. Mono-disperse tetra-(C12E4), hexa-(C12E6) and octa-ethyleneglycol mono-n-dodecyl ether (C12E8), and poly-disperse eicosa-ethyleneglycol mono-n-tetradecyl ether (C14EO20) are respectively employed. Fluorescence and circular dichroism measurements are performed at surfactant/protein molar ratios (rm)s lower and higher than one. We aim to get new insights into the binding mechanism of these species and to differentiate among the interaction abilities of these surfactants. The relative magnitude of the binding thermodynamic parameters by fluorescence, and the increase of α-helix prove that hydrogen bonding drives the interaction next to the hydrophobic attraction. C12En (n = 4,6,8) develop more H bonds with the albumin than C14EO20 owing to a zigzag conformation of their short ethyleneoxide chains. Among the homologous surfactants, C12E6 has a slightly stronger interaction with BSA due to a maximal number of H bonds at a minimal hindering. Static fluorescence and dynamic fluorescence indicate an inter-conversion between the tryptophan (Trp) rotamers which happens around the surfactants critical micellar concentration. For C14EO20, the meander conformation of the polar group determines a less evident conversion of the Trp rotamers and smaller α-helix rise. Binding isotherms of the homologous surfactants and the fluorescence quenching mechanism by C12E6 are also provided.

Keywords
Bovine serum albumin; Ethoxylated nonionic surfactants; Fluorescence; Binding thermodynamic parameters; α-Helix; Hydrogen bonding
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A combined binding mechanism of nonionic ethoxylated surfactants to bovine serum albumin revealed by fluorescence and circular dichroism
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 153, December 2015, Pages 198–205
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us