Influence of protein conformation on frictional properties of poly (vinyl alcohol) hydrogel for artificial cartilage
Influence of protein conformation on frictional properties of poly (vinyl alcohol) hydrogel for artificial cartilage
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DOI：
10.1007/s11249-006-9185-6
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发表时间：
2007-05-01
影响因子：
3.2
通讯作者：
Murakami, T.
中科院分区：
文献类型：
--
作者：
Nakashima, K.;Sawae, Y.;Murakami, T.
聚乙烯醇(PVA)水凝胶是人工软骨的理想材料之一。在我们以前的研究中，PVA水凝胶的磨损与润滑剂中蛋白质的含量有关。用圆二色谱研究了牛血清白蛋白(BSA)和人丙种球蛋白(HGG)的二级结构，以阐明蛋白质对摩擦性能的影响。BSA和HGG主要由α-螺旋和β-折叠组成。在混合或边界润滑模式下，含有α-螺旋结构的牛血清白蛋白表现出比由β-折叠结构组成的HGG低的摩擦力。α-螺旋结构形成低剪切层，因为α-螺旋结构容易从表面释放，粘结强度低。HGG形成了均匀的吸附层，但在与单一蛋白质的摩擦中表现出比BSA更大的摩擦力。然而，在润滑剂从HGG到BSA的反复摩擦中，由于形成了最佳的蛋白质层状结构，最终的摩擦力降低了。因此，蛋白质的层状结构在保护摩擦表面和减少摩擦方面起着重要的作用。在热处理试验中，由于α-螺旋结构的减少，热诱导牛血清白蛋白表现出很低的摩擦。热致HGG与天然HGG差异不大，但不能与热致BSA产生低摩擦力。由此可见，蛋白质构象对摩擦力有有效的影响。
Poly (vinyl alcohol) (PVA) hydrogel is one of the anticipated materials for artificial cartilage. In our previous studies, wear of PVA hydrogel depended on content of proteins in lubricants. The secondary structures of bovine serum albumin (BSA) and human gamma globulin (HGG) were investigated in circular dichroism spectroscopy to clarify the influence of the proteins on frictional properties. BSA and HGG were mainly composed of the alpha-helix and the beta-sheet, respectively. BSA containing the alpha-helix structure showed low friction compared to HGG composed of the beta-sheet structure in mixed or boundary lubrication mode. The alpha-helix structure forms low shear layer because the alpha-helix structure is easily released from surfaces and low cohesive strength. HGG forms uniform adsorption layer, but showed higher friction than BSA in the rubbing with single protein. In the repeated rubbing with changing of lubricants from HGG to BSA, however, the final friction was reduced, because an optimum layered structure of proteins was formed. Hence, layered structure of proteins appears to play an important role to protect rubbing surfaces and to reduce friction. In heat treatment tests, heat-induced BSA showed very low friction because of reduction of the alpha-helix structure. Heat-induced HGG did not show large differences from native HGG, but could not bring low friction with heat-induced BSA. Thus it was shown that the protein conformation has effective influences on friction.