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首页> 外文期刊>Biomaterials >Adsorption of a therapeutic enzyme to self-assembled monolayers: effect of surface chemistry and solution pH on the amount and activity of adsorbed enzyme.
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Adsorption of a therapeutic enzyme to self-assembled monolayers: effect of surface chemistry and solution pH on the amount and activity of adsorbed enzyme.

机译：治疗性酶对自组装单层的吸附：表面化学和溶液pH值对吸附酶的量和活性的影响。

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摘要

The adsorption of a therapeutic enzyme to self-assembled monolayers (SAMs) of different functionalities (X=CH(3)-, OH- and COOH-) was evaluated as a function of solution pH. Radiolabelling studies showed that the enzyme has higher affinity for hydrophobic surfaces than for hydrophilic surfaces, and that the highest adsorption was obtained at the more acidic pH values (4.5 and 5.5), despite the type of surface. IRAS and XPS measurements confirmed this tendency. Dye-binding studies and fluorescence quenching were used to investigate if a pH variation induces any conformational changes on the enzyme. Both methods suggest that lowering the pH from physiological to acidic values triggers an increased exposure of non-polar sites in the enzyme, which may modulate its adsorption behaviour to the more hydrophobic surfaces. At pH 4.5, the enzyme carries a substantial positive net charge and therefore relatively low native-state stability. As a consequence, surface binding may be favoured, irrespective of the type of surface, by providing increased conformational entropy to the enzyme. The specific activity (SA) of the adsorbed enzyme was strongly dependent on the conditions used. A decrease in SA (ca. 30% of control) was observed after adsorption on CH(3)-SAMs for all the pH tested. Adsorption on gold and on the more hydrophilic SAMs (OH- and COOH-) resulted in different degrees of inactivation at the more acidic pH (4.5), and in enzyme activation (up to ca. 230% of control) at higher pH (7-8), near the isoelectric point of the enzyme.
机译：根据溶液pH值评估了治疗性酶对不同功能（X = CH（3）-，OH-和COOH-）自组装单分子膜（SAMs）的吸附。放射性标记研究表明，该酶对疏水表面的亲和力高于对亲水表面的亲和力，并且尽管表面类型不同，但在更酸性的pH值（4.5和5.5）下可获得最高的吸附。 IRAS和XPS测量证实了这种趋势。染料结合研究和荧光猝灭用于研究pH的变化是否引起酶的任何构象变化。两种方法都表明，将pH从生理值降低到酸性值会触发酶中非极性位点的暴露增加，这可能会调节其对疏水性更高的表面的吸附行为。在pH 4.5时，该酶带有大量正净电荷，因此相对较低的自然状态稳定性。结果，通过增加酶的构象熵，可能有利于表面结合，而与表面的类型无关。吸附的酶的比活性（SA）在很大程度上取决于所使用的条件。对于所有测试的pH，在CH（3）-SAMs上吸附后，观察到SA的减少（约为对照的30％）。在金和更亲水的SAMs（OH-和COOH-）上的吸附在更高的pH（4.5）下导致不同程度的失活，而在更高的pH（7达到对照的230％）时导致酶活化。 -8），在酶的等电点附近。

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