Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark.
Department of Mechanical Engineering, Technical University of Denmark, DK-2800, Kgs. Lyngby, Denmark; Institute of Functional Surfaces, School of Mechanical Engineering, University of Leeds, LS2 JT9, Leeds, The United Kingdom.
Colloids Surf B Biointerfaces. 2024 Jun;238:113924. doi: 10.1016/j.colsurfb.2024.113924. Epub 2024 Apr 21.
β-lactoglobulin (BLG) is the major whey protein with negative charges at neutral pH in aqueous media. Thus, the interaction with mucins, the major polyanionic component of mucus, is very weak due to the electrostatic repulsion between them. The present study postulates that cationization of BLG molecules may reverse the interaction characteristics between BLG and mucin from repulsive to associative. To this end, cationic-modified BLGs were prepared by grafting positively charged ethylenediamine (EDA) moieties into the negatively charged carboxyl groups on the aspartic and glutamic acid residues and compared with non-modified BLG upon mixing with porcine gastric mucin (PGM). To characterize the structural and conformational features of PGM, non/cationized BLGs, and their mixtures, various spectroscopic approaches, including zeta potential, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed. Importantly, we have taken surface adsorption with optical waveguide lightmode spectroscopy (OWLS), and tribological properties with pin-on-disk tribometry at the sliding interface as the key approaches to determine the interaction nature between them as mixing PGM with polycations can lead to synergistic lubrication at the nonpolar substrate in neutral aqueous media as a result of an electrostatic association. All the spectroscopic studies and a substantial improvement in lubricity collectively supported a tenacious and associative interaction between PGM and cationized BLGs, but not between PGM and non-modified BLG. This study demonstrates a unique and successful approach to intensify the interaction between BLG and mucins, which is meaningful for a broad range of disciplines, including food science, macromolecular interactions, and biolubrication etc.
β-乳球蛋白（BLG）是乳清蛋白中的主要成分，在水介质中带负电荷，在中性 pH 值下。因此，由于它们之间的静电排斥，与粘蛋白（粘液的主要多阴离子成分）的相互作用非常弱。本研究假设 BLG 分子的阳离子化可能会使 BLG 与粘蛋白之间的相互作用特征从排斥变为缔合。为此，通过将带正电荷的乙二胺（EDA）部分接枝到天冬氨酸和谷氨酸残基上的带负电荷的羧基上，制备了阳离子化的 BLG，并与猪胃粘蛋白（PGM）混合后与非改性 BLG 进行了比较。为了表征 PGM、非/阳离子化 BLG 及其混合物的结构和构象特征，采用了各种光谱方法，包括 zeta 电位、动态光散射（DLS）和圆二色性（CD）光谱法。重要的是，我们采用光波导光模光谱（OWLS）进行表面吸附，以及针盘摩擦仪在滑动界面上的摩擦学特性作为关键方法来确定它们之间的相互作用性质，因为将 PGM 与聚阳离子混合会导致在中性水介质中非极性基底上产生协同润滑由于静电缔合。所有的光谱研究和润滑性能的显著提高都共同支持了 PGM 和阳离子化 BLG 之间的牢固和缔合相互作用，而不是 PGM 和非改性 BLG 之间的相互作用。该研究展示了一种增强 BLG 与粘蛋白相互作用的独特而成功的方法，这对于包括食品科学、高分子相互作用和生物润滑等在内的广泛学科都具有重要意义。
