PICOSECOND OPTICAL STUDIES IN PROTEINS

这项拟议研究的具体目标是确定振动 能量在生物聚合物系统中传播。能量机制 在蛋白质中的传播和分散是微观研究的中心 对大振幅相关核运动的理解。结构性 特定刺激的变化是已知的重要因素 对活动的监管。血红蛋白中O2亲和力的变构控制， 肌肉收缩和DNA解体只是几个例子。 长期以来，生物力学一直被认为是生物力学中的重要组成部分 对活动的监管。鉴于这个问题的重要性，有几个 理论模型已经被开发出来，以处理巨大的 在运动中耦合的原子核的数目和在运动中 运动的时间刻度。从非色散孤子到孤子的理论 (振动波包)到全尺度的分子动力学计算 都被雇佣了。拟议的研究构成了第一个直接的研究 对这个问题的实验方法。Soret中的光激发 血红素蛋白区域提供了一种选择性的方式将能量储存到 蛋白质中明确的空间位置。通过使用实时 全息术具有光学外差探测的新特征， 光能到振动模的随机化和 能量从血红素中心传播到蛋白质外部 水层可以以100fsec的分辨率跟踪。光外差 检测起到放大信号的作用，并使得能够检测到更少的 10-80摄氏度内能温度变化。通过研究热门乐队 空间上起源于血红素中心的转变，酪氨酸残基在 蛋白质骨架和水的外部，详细绘制了空间地图 可以得到能量传播的轮廓和动力学。这些结果 可以与最近的分子动力学模拟相比较。慢速构造 由CO和O2光解引发的驰豫过程也将是 通过密度跟踪水晶格的变化来研究的 对实时全息图像的贡献。重点将放在 关于配基结合过程中能量传递第一步的关联 或光解离对大幅度结构反应的影响 刺激。这些研究将使首次能够检查 从100毫秒到毫秒的所有时间尺度上的蛋白质动力学。

The specific goal of the proposed research is to determine how vibrational energy propagates in biopolymer systems. The mechanism of energy propagation and dispersion in proteins is central to a microscopic understanding of large amplitude correlated nuclear motion. Structural changes to a specific stimulus are known to be important factors in regulation of activity. Allosteric control of O2 affinity in hemoglobin, muscle contraction and the unwinding of DNA are just a few examples. Biomechanics has long been recognized as an essential component in the regulation of activity. Given the importance of the problem, several theoretical models have been developed to come to grips with the enormous number of nuclei coupled in the motion and the apparent contradiction in time scales for the motions. Theories ranging from nondispersive solitons (vibrational wave packets) to full scale molecular dynamics calculations have been employed. The proposed research constitutes the first direct experimental approach to this problem. Optical excitation in the Soret region of heme proteins provides a selective means to deposit energy into a well defined spatial position in the protein. By use of real-time holography with the novel feature of optical heterodyne detection, the randomization of the optical energy into vibrational modes and the propagation of that energy from the heme center to the protein exterior water layer can be followed with 100 fsec resolution. Optical heterodyne detection acts to amplify the signal and enables the detection of less that 10-80C temperature changes in internal energy. By studying hot band transitions originating spatially from the heme center, tryosine residue in the protein backbone and water exterior, a detailed mapping of the spatial profile and dynamics of the energy propagation can be made. These results can be compared to recent molecular dynamics simulations. Slow structural relaxation processes triggered by CO and O2 photodissociation will also be studied by following changes in the aqueous lattice through density contributions to the real-time holographic image. Emphasis will be place on correlating the first steps in energy transduction during ligand binding or photodissociation to the large amplitude structural responses to the stimulus. These studies will allow for the very first time examination of protein dynamics on all timescales, from the 100 fsec to the msec regime.