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Issue 59, 2014
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Microscopic and thermodynamic analysis of PEG–β-lactoglobulin interaction

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Abstract

We report the binding of milk β-lactoglobulin (β-LG) with PEG-3000, PEG-6000 and methoxypoly(ethylene glycol) anthracene (mPEG-anthracene) in aqueous solution at pH 7.4, using multiple spectroscopic methods, thermodynamic analysis, transmission electron microscopy (TEM) and molecular modeling. Thermodynamic and spectroscopic analysis showed that polymers bind β-LG via van der Waals interactions, hydrogen bonding and hydrophobic interactions, with overall binding constants KPEG-3000–β-LG = 9.2 (±0.9) × 103 M−1, KPEG-6000–β-LG = 9.7 (±0.7) × 103 M−1 and KmPEG-anthracene–β-LG = 5.5 (±0.5) × 104 M−1. The binding affinity was mPEG-anthracene > PEG-6000 > PEG-3000. Transmission electron microscopy analysis showed significant changes in protein morphology as polymer–protein complexation occurred, with a major increase in the diameter of the protein aggregate. Modeling showed several hydrogen bonding systems between PEG and the different amino acid stabilized polymer–β-LG complexes. The free binding energy indicated that the interaction process is spontaneous at room temperature. Furthermore, mPEG-anthracene is a stronger protein binder than PEG-3000 and PEG-6000, due to its major hydrophobic characteristics.

Graphical abstract: Microscopic and thermodynamic analysis of PEG–β-lactoglobulin interaction

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Article information


Submitted
11 Apr 2014
Accepted
26 Jun 2014
First published
26 Jun 2014

RSC Adv., 2014,4, 31084-31093
Article type
Paper
Author version available

Microscopic and thermodynamic analysis of PEG–β-lactoglobulin interaction

L. Bekale, P. Chanphai, S. Sanyakamdhorn, D. Agudelo and H. A. Tajmir-Riahi, RSC Adv., 2014, 4, 31084
DOI: 10.1039/C4RA03303E

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