Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides.
Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides.
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使用单模集成光波导宽带光谱研究吸附在氧化铝表面上的细胞色素 c 亚单层的 Q 和 CT 能带。
DOI：
10.1021/jp810845e
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Mendes,SergioB
中科院分区：
文献类型：
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作者：
Wiederkehr,RodrigoS;Hoops,GeoffreyC;Aslan,MustafaM;Byard,CourtneyL;Mendes,SergioB
在这项工作中，我们报告了细胞色素在不同亚单层水平上吸附在氧化铝波导表面的摩尔吸收率的实验结果；我们的数据表明，蛋白质的光学性质明显依赖于它的表面密度。测量是使用宽带、单模、集成光波导光谱技术进行的，这是一种非常敏感的工具，能够达到此类研究所需的亚单层检测水平。本研究重点研究了表面吸附cytc的q波段（中心为525 nm）的摩尔吸收率，并首次研究了表面吸附cytc的弱电荷转移（CT）波段（中心为695 nm）。将光谱范围为450 ~ 775 nm的偏振光全部耦合到氧化铝薄膜中，形成单模平面光波导。采用原子层沉积法将厚度为180nm的氧化铝薄膜波导沉积在玻璃基板上。在中性ph的缓冲水溶液中，通过静电吸附在氧化铝波导表面形成蛋白质亚单层。在缓冲水溶液中，体积蛋白质浓度在5 nM至8200 nM范围内，研究了表面吸附细胞的光学性质。对于表面密度为2.3 pmol/cm2的蛋白质，在电荷转移带处测量的摩尔吸收率为335 M−1cm−1，对于表面密度为15 pmol/cm2的蛋白质，其摩尔吸收率为720 M−1cm−1，这与溶解在水中性缓冲液中的细胞的值（830 M−1cm−1）非常接近。蛋白质摩尔吸收率的改变及其对表面密度的依赖很可能归因于表面吸附物质的构象变化。
In this work, we report experimental results on the molar absorptivity of cytochromecadsorbed at different submonolayer levels onto an aluminum oxide waveguide surface; our data show a clear dependence of the protein optical properties on its surface density. The measurements were performed using the broadband, single-mode, integrated optical waveguide spectroscopic technique, which is an extremely sensitive tool able to reach submonolayer levels of detection required for this type of studies. This investigation focuses on the molar absorptivity at the Q-band (centered at 525 nm) and, for the first time to our knowledge, the weak charge transfer (CT) band (centered at 695 nm) of surface-adsorbed cytc. Polarized light in the spectral region from 450 to 775 nm was all-coupled into an alumina thin film, which functioned as a single-mode planar optical waveguide. The alumina thin-film waveguide used for this work had a thickness of 180 nm and was deposited on a glass substrate by the atomic layer deposition process. The protein submonolayer was formed on the alumina waveguide surface through electrostatic adsorption from an aqueous buffer solution at neutral pH. The optical properties of the surface-adsorbed cytcwere investigated for bulk protein concentrations ranging from 5 nM to 8200 nM in the aqueous buffer solution. For a protein surface density of 2.3 pmol/cm2, the molar absorptivity measured at the charge transfer band was 335 M−1cm−1, and for a surface density of 15 pmol/cm2was 720 M−1cm−1, which is much closer to the value of cytcdissolved in an aqueous neutral buffer (830 M−1cm−1). The modification of the protein molar absorptivity and its dependence on the surface density can most likely be attributed to conformational changes of the surface-adsorbed species.