Department of Electronic Science and Engineering, Kyoto University, Kyoto University Katsura, Nishikyo, Kyoto 615-8510, Japan.
Device Solutions Center, Panasonic Corporation, Yagumo-naka-machi 3-1-1, Moriguchi, Osaka 570-8501, Japan.
Nat Mater. 2014 Mar;13(3):264-70. doi: 10.1038/nmat3847. Epub 2014 Jan 19.
The conformational flexibility of antibodies in solution directly affects their immune function. Namely, the flexible hinge regions of immunoglobulin G (IgG) antibodies are essential in epitope-specific antigen recognition and biological effector function. The antibody structure, which is strongly related to its functions, has been partially revealed by electron microscopy and X-ray crystallography, but only under non-physiological conditions. Here we observed monoclonal IgG antibodies in aqueous solution by high-resolution frequency modulation atomic force microscopy (FM-AFM). We found that monoclonal antibodies self-assemble into hexamers, which form two-dimensional crystals in aqueous solution. Furthermore, by directly observing antibody-antigen interactions using FM-AFM, we revealed that IgG molecules in the crystal retain immunoactivity. As the self-assembled monolayer crystal of antibodies retains immunoactivity at a neutral pH and is functionally stable at a wide range of pH and temperature, the antibody crystal is applicable to new biotechnological platforms for biosensors or bioassays.
抗体在溶液中的构象灵活性直接影响其免疫功能。具体来说，免疫球蛋白 G（IgG）抗体的柔性铰链区域对于抗原的表位特异性识别和生物效应功能至关重要。尽管电子显微镜和 X 射线晶体学已经部分揭示了与抗体功能密切相关的结构，但这些结构仅在非生理条件下才能被观察到。在这里，我们通过高分辨率调频原子力显微镜（FM-AFM）观察到了水溶液中的单克隆 IgG 抗体。我们发现单克隆抗体可以自组装成六聚体，在水溶液中形成二维晶体。此外，通过直接使用 FM-AFM 观察抗体-抗原相互作用，我们揭示了晶体中的 IgG 分子保留了免疫活性。由于抗体的自组装单层晶体在中性 pH 值下保持免疫活性，并且在广泛的 pH 值和温度范围内功能稳定，因此抗体晶体适用于生物传感器或生物测定的新型生物技术平台。
