CONFORMATION AND ELECTRONIC STRUCTURE OF BIOLOGICAL MOLECULES

生物分子的构象和电子结构

• 批准号: 3940616
• 负责人: W A EATON
• 金额: --
• 依托单位: NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/3940616
• 关键词: Raman spectrometry; atomic absorption spectrometry; birefringences; carbon monoxide; chemical structure function; conformation; dichroism; heme; hemoglobin As; hemoprotein structure; laser spectrometry; ligands; molecular energy level; photolysis; quantum chemistry

Time resolved optical spectroscopy with nanosecond lasers and molecular dynamics calculations have been employed to investigate ligand rebinding and conformational changes in hemoglobin subsequent to photodissociation of the carbon monoxide complex. In order to precisely measure the time course of the changes in the conformation of the deoxy photoproduct, which produce small spectral changes, as well as to determine the kinetics of ligand rebinding, as automated, sensitive nanosecond spectrometer has been developed to measure time-resolved spectra. The spectra have been analyzed using singular value decomposition to produce a set of orthonormal basis spectra and the time course of their amplitudes. With these techniques the kinetics of ligand rebinding and conformational changes have been studied with hemoglobins initially in the R and T quaternary structure. The R to T quaternary transition is observed for the completely unliganded R state molecule to occur at about 0.02 ms, while both R and T state molecules show tertiary conformational relaxations at about 50 ns and 500 ns. The 50 ns relaxation is simultaneous with geminate rebinding, suggesting that it is caused by motion of the ligand out of the heme pocket. Using the simplest kinetic model, a comparison of the geminate kinetics for R and T state molecules indicate that the difference in the factor of about 50 in the overall rate of ligand binding to the R and T states can be explained by differences in binding rates to the heme from within the heme pocket. Changes in the barriers to motion of the ligand inside the protein or between the protein and the solvent appear to play a minor role in determining the difference in overall rates. The photodissociation process is being simulated using the technique of molecular dynamics, which describes the motion of the individual atoms. Calculations on a complete tetramer in vacuo show that the heme conformation change is a sub- picosecond process and that the excess vibrational energy of the heme is deposited in the surrounding protein in about 20 ps. The trajectories are being analyzed to determine the response of the globin conformation to the change in heme conformation.

时间通过纳秒激光解析光谱法和 分子动力学计算已采用 研究配体重新固定和构象变化 碳的光解离后血红蛋白 一氧化物复合物。 为了精确衡量时间课程 脱氧光产物构象的变化， 会产生较小的光谱变化，并确定 自动化，敏感的纳米秒 已经开发了光谱仪以测量时间分辨 光谱。 使用单数值对光谱进行了分析 分解以产生一组正直基谱和 他们振幅的时间过程。 使用这些技术 配体重构和构象变化的动力学已经 最初在R和T季前研究中使用血红蛋白进行研究 结构。 观察到的r到第四纪转变 完全无配合的R状态分子发生在约0.02 MS，而R和T状态分子均显示三级 大约50 ns和500 ns的构象放松。 50 ns 放松是同时饰有geminate重新扎的，暗示 它是由配体从血红素口袋中运动引起的。 使用最简单的动力学模型，Geminate的比较 R和T状态分子的动力学表明差异 在配体结合的总体速率中约为50倍 R和T状态可以通过绑定的差异来解释 血红素口袋内的血红素率。 变化 蛋白质内或在蛋白质内运动的障碍 蛋白质和溶剂似乎在确定 总比率差异。 使用的光解离过程正在使用 分子动力学技术，描述了运动的运动 个体原子。 在完整的四聚体上计算 真空表明，血红素构象变化是一个子 picsecond的过程和过多的振动能 血红素在大约20 ps中沉积在周围蛋白质中。 这 正在分析轨迹以确定 球蛋白构象对血红素构象的变化。