Conformational Flexibility and Self-Association of Fibrinogen in Concentrated Solutions.
Conformational Flexibility and Self-Association of Fibrinogen in Concentrated Solutions.
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DOI：
10.1021/acs.jpcb.7b05654
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发表时间：
2017-08
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通讯作者：
Y. Zuev;R. Litvinov;A. E. Sitnitsky;B. Idiyatullin;D. R. Bakirova;D. Galanakis;A. Zhmurov;V. Barsegov;J. Weisel
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作者：
Y. Zuev;R. Litvinov;A. E. Sitnitsky;B. Idiyatullin;D. R. Bakirova;D. Galanakis;A. Zhmurov;V. Barsegov;J. Weisel
我们使用脉冲场梯度1H NMR-扩散法研究了纤维蛋白原（一种参与血液凝固的血浆蛋白）在0.3-60 mg/mL浓度和5-42 °C温度范围内的流体动力学行为。Arrhenius图显示纤维蛋白原扩散的活化能艾德= 21.3 kJ/mol（1.4 mg/mL）和28.4 kJ/mol（38 mg/mL）。我们发现，纤维蛋白原自扩散的浓度开始在1.7-3.4毫克/毫升，这偏离了标准的硬颗粒的行为，这表明一个显着的分子间纠缠显着放缓。无论是否存在GPRP肽（纤维蛋白聚合抑制剂），以及在不含纤维蛋白寡聚体的样品中，均观察到这种浓度依赖性。相比之下，具有截短的Aα链C-末端部分的纤维蛋白原变体I-9的扩散率的浓度依赖性要小得多，表明αC区域形成的分子间键的重要性。结合全原子分子动力学模拟的理论模型揭示了部分弯曲的纤维蛋白原溶液的构象，插入之间的一个灵活的链和一个刚性棒中观察到的晶体。所得结果阐明了αC区通过形成控制纤维蛋白原溶液整体性质的弱分子间键在调节纤维蛋白原分子形状中的重要作用。
We studied the hydrodynamic behavior of fibrinogen, a blood plasma protein involved in blood clotting, in a broad 0.3-60 mg/mL range of concentration and 5-42 °C temperature using pulsed-field gradient 1H NMR-diffusometry. Arrhenius plots revealed the activation energy for fibrinogen diffusion Ed = 21.3 kJ/mol at 1.4 mg/mL and 28.4 kJ/mol at 38 mg/mL. We found a dramatic slowdown in fibrinogen self-diffusion with concentration beginning at 1.7-3.4 mg/mL, which deviated from the standard hard-particle behavior, suggesting a remarkable intermolecular entanglement. This concentration dependence was observed regardless of the absence or presence of the GPRP peptide (inhibitor of fibrin polymerization), and also in samples free of fibrin oligomers. By contrast, diffusivity of fibrinogen variant I-9 with truncated C-terminal portions of the Aα chains was much less concentration-dependent, indicating the importance of intermolecular linkages formed by the αC regions. Theoretical models combined with all-atom molecular dynamics simulations revealed partially bent fibrinogen solution conformations that interpolate between a flexible chain and a rigid rod observed in the crystal. The results obtained illuminate the important role of the αC regions in modulating the fibrinogen molecular shape through formation of weak intermolecular linkages that control the bulk properties of fibrinogen solutions.