Frederix Patrick L T M, Bosshart Patrick D, Akiyama Terunobu, Chami Mohamed, Gullo Maurizio R, Blackstock Jason J, Dooleweerdt Karin, de Rooij Nico F, Staufer Urs, Engel Andreas
M E Müller Institute for Structural Biology, Biozentrum of the University of Basel, CH-4056 Basel, Switzerland.
Nanotechnology. 2008 Sep 24;19(38):384004. doi: 10.1088/0957-4484/19/38/384004. Epub 2008 Aug 12.
Four different conductive supports are analysed regarding their suitability for combined atomic force and scanning electrochemical microscopy (AFM-SECM) on biological membranes. Highly oriented pyrolytic graphite (HOPG), MoS(2), template stripped gold, and template stripped platinum are compared as supports for high resolution imaging of reconstituted membrane proteins or native membranes, and as electrodes for transferring electrons from or to a redox molecule. We demonstrate that high resolution topographs of the bacterial outer membrane protein F can be recorded by contact mode AFM on all four supports. Electrochemical feedback experiments with conductive cantilevers that feature nanometre-scale electrodes showed fast re-oxidation of the redox couple Ru(NH(3))(6)(3+/2+) with the two metal supports after prolonged immersion in electrolyte. In contrast, the re-oxidation rates decayed quickly to unpractical levels with HOPG or MoS(2) under physiological conditions. On HOPG we observed heterogeneity in the re-oxidation rate of the redox molecules with higher feedback currents at step edges. The latter results demonstrate the capability of conductive cantilevers with small electrodes to measure minor variations in an SECM signal and to relate them to nanometre-scale features in a simultaneously recorded AFM topography. Rapid decay of re-oxidation rate and surface heterogeneity make HOPG or MoS(2) less attractive for combined AFM-SECM experiments on biological membranes than template stripped gold or platinum supports.
针对四种不同的导电基底，分析了它们在生物膜上用于原子力显微镜与扫描电化学显微镜联用（AFM-SECM）的适用性。比较了高度取向热解石墨（HOPG）、二硫化钼（MoS₂）、模板剥离金和模板剥离铂作为重构膜蛋白或天然膜高分辨率成像的基底，以及作为氧化还原分子电子传递电极的性能。我们证明，通过接触模式原子力显微镜可以在所有这四种基底上记录细菌外膜蛋白F的高分辨率形貌图。使用具有纳米级电极的导电悬臂进行的电化学反馈实验表明，在长时间浸入电解质后，两种金属基底上氧化还原对Ru(NH₃)₆³⁺/²⁺的再氧化速度很快。相比之下，在生理条件下，HOPG或MoS₂上的再氧化速率迅速衰减至不实用的水平。在HOPG上，我们观察到氧化还原分子再氧化速率的异质性，在台阶边缘处具有更高的反馈电流。后一结果表明，带有小电极的导电悬臂能够测量SECM信号中的微小变化，并将其与同时记录的AFM形貌中的纳米级特征相关联。再氧化速率的快速衰减和表面异质性使得HOPG或MoS₂在生物膜的联合AFM-SECM实验中不如模板剥离金或铂基底有吸引力。
