Microscopic and thermodynamic analysis of PEG-beta-lactoglobulin interaction

作者：Bekale L; Chanphai P; Sanyakamdhorn S; Agudelo D; Tajmir Riahi H A^*

来源：RSC Advances, 2014, 4(59): 31084-31093.

DOI：10.1039/c4ra03303e

We report the binding of milk beta-lactoglobulin (beta-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 beta-LG via van der Waals interactions, hydrogen bonding and hydrophobic interactions, with overall binding constants KPEG-3000-beta-LG = 9.2 (+/- 0.9) x 10(3) M-1, KPEG-6000-beta-LG = 9.7 (+/- 0.7) x 10(3) M-1 and KmPEG-anthracene-beta-LG = 5.5 (+/- 0.5) x 10(4) 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-beta-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.

• 出版日期2014