Hanson D C, Schumaker V N
J Mol Biol. 1985 Jun 5;183(3):377-83. doi: 10.1016/0022-2836(85)90008-7.
The rotational dynamics of rabbit immunoglobulin G (IgG) anti-dansyl antibodies bound to the C1q subcomponent of human complement were studied by nanosecond fluorescence spectroscopy. Deconvoluted anisotropy decays of IgG-C1q mixtures were fitted to a two-exponential expression and were corrected for the effects of unbound IgG, which was determined with an analytical ultracentrifuge. Compared with the anisotropy parameters for free IgG, the pre-exponential weighting factors and the short correlation time of the C1q-bound antibody were nearly unchanged, and the long correlation time increased by only about 45 nanoseconds. These results, together with rotational diffusion calculations, indicate that the Fab arms of the C1q-bound antibody exhibited considerable flexibility. This finding may have biological relevance because it suggests that C1q can bind to the Fc segments of IgG molecules anchored in an immune complex, even though the angles between the two Fab arms of the different antibodies may vary. The results of this study also support our earlier interpretation that both the short and long correlation times of IgG principally represent flexible motions of the Fab segments.
通过纳秒荧光光谱法研究了与人类补体C1q亚成分结合的兔免疫球蛋白G（IgG）抗丹磺酰抗体的旋转动力学。将IgG-C1q混合物的去卷积各向异性衰减拟合为双指数表达式，并对未结合IgG的影响进行校正，未结合IgG的量通过分析超速离心机测定。与游离IgG的各向异性参数相比，C1q结合抗体的指数前加权因子和短相关时间几乎不变，长相关时间仅增加约45纳秒。这些结果与旋转扩散计算一起表明，C1q结合抗体的Fab臂表现出相当大的灵活性。这一发现可能具有生物学意义，因为它表明C1q可以结合锚定在免疫复合物中的IgG分子的Fc段，即使不同抗体的两个Fab臂之间的角度可能不同。本研究结果也支持我们早期的解释，即IgG的短和长相关时间主要代表Fab段的灵活运动。
