Acuña Sergio M, Bastías José M, Toledo Pedro G
Department of Food Engineering, University of Bío-Bío, Chillán, Chile.
Department of Chemical Engineering and Laboratory of Surface Analysis, University of Concepción, Correo 3, Concepción, Chile.
PLoS One. 2017 Mar 15;12(3):e0173910. doi: 10.1371/journal.pone.0173910. eCollection 2017.
The net interaction between a probe tip coated with bovine serum albumin (BSA) protein and a flat substrate coated with poly(ethylene oxide) (PEO) polymer was measured directly on approach in water and electrolyte solutions using AFM. The approach force curve between the two surfaces was monotonically repulsive in water and in electrolyte solutions. At pH ~5, slightly above the isoelectric point (pI) of BSA, and at large distances, the force was dominated by electrostatic repulsion between the oxygen atoms of the incoming protein with those belonging to the ether groups of PEO. Such repulsive force and range decreased in NaCl. Under physiological conditions, pH 6, BSA is definitely charged and the electrostatic repulsion with ether groups in PEO appears at larger separation distances. Interestingly, at pH 4, below the pI of BSA, the repulsion decreased because of an attractive, although weak, electrostatic force that appeared between the ether groups in PEO and the positively charged amino groups of BSA. However, for all solution conditions, once compression of PEO begun, the net repulsion was always dominated by short-range polymeric steric repulsion and repulsive enthalpy penalties for breaking PEO-water bonds. Results suggest that PEO in mushroom conformation may also be effective in reducing biofouling.
使用原子力显微镜（AFM），直接测量了涂有牛血清白蛋白（BSA）蛋白的探针尖端与涂有聚环氧乙烷（PEO）聚合物的平面基底在水和电解质溶液中接近时的净相互作用。在水和电解质溶液中，两个表面之间的接近力曲线呈单调排斥。在pH约为5（略高于BSA的等电点（pI））且距离较大时，力主要由进入的蛋白质的氧原子与PEO的醚基的氧原子之间的静电排斥作用主导。这种排斥力和范围在NaCl中减小。在生理条件下，pH为6时，BSA肯定带电，与PEO中的醚基的静电排斥作用出现在更大的分离距离处。有趣的是，在pH为4（低于BSA的pI）时，排斥力降低，这是因为在PEO的醚基与BSA带正电的氨基之间出现了一种吸引力（尽管较弱）的静电力。然而，对于所有溶液条件，一旦开始压缩PEO，净排斥力总是由短程聚合物空间排斥力和破坏PEO-水键的排斥焓罚主导。结果表明，蘑菇状构象的PEO在减少生物污染方面也可能是有效的。
