Ultrafast Dynamics of Resonance Energy Transfer in Myoglobin: Probing Local Conformation Fluctuations
Ultrafast Dynamics of Resonance Energy Transfer in Myoglobin: Probing Local Conformation Fluctuations
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DOI：
10.1021/jp910013f
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发表时间：
2010-01-28
影响因子：
3.3
通讯作者：
Zhong, Dongping
中科院分区：
文献类型：
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作者：
Stevens, Jeffrey A.;Link, Justin J.;Zhong, Dongping
我们在这里报告我们的固有色氨酸和肌红蛋白中的人工血红素基团之间的共振能量转移的系统表征，以开发一种新的能量转移对作为血红素蛋白的分子统治者，以研究局部构象波动。利用定点突变技术，我们在肌红蛋白A-螺旋上沿着设计了四个色氨酸突变体，每个突变体只含有一个色氨酸-血红素能量传递对。在飞秒分辨率下，即使在15-25埃的分离距离下，我们也观察到数十至数百皮秒的超快能量转移。在这些时间尺度上，供体和受体不能被随机化，并且福斯特能量转移中的取向因子受到高度限制。因此，在不同的突变位点的取向因子的变化的直接测量揭示了相对的局部结构的灵活性和螺旋形成的波动，特别是在这里证明的色氨酸7和14的位置。更重要的是，局部环境弛豫与能量传递动力学的时间尺度相似，导致非平衡动力学过程。利用飞秒和波长分辨的荧光动力学，我们能够确定这种非平衡态能量传递动力学的时间尺度，并阐明由局部动力学不均匀性和/或局部环境弛豫引起的非指数能量传递动力学的机制。
We report here Our systematic characterization of resonance energy transfer between intrinsic tryptophan and the prosthetic heme group in myoglobin in order to develop a novel energy-transfer pair as a molecular ruler in heme proteins to Study local conformation fluctuations. With site-directed mutagenesis, we designed four tryptophan Mutants along the A-helix of myoglobin and each mutant contains only a single tryptophan-heme energy-transfer pair. With femtosecond resolution, we observed, even at separation distances of 15-25 angstrom, Ultrafast energy transfer in tens to hundreds of picoseconds. On these time scales, the donor and acceptor cannot be randomized and the orientation factor in Forster energy transfer is highly restricted. Thus, direct measurement of the orientation-factor changes at different mutation sites reveals relative local structure flexibility and coil formation fluctuations as particularly demonstrated here for positions of tryptophan 7 and 14. More importantly, the local environment relaxation Occurs on the similar time scales of the energy transfer dynamics, resulting in a nonequilibrium dynamic process. With femtosecond- and wavelength-resolved fluorescence dynamics, we are able to determine the time scales of such nonequilibrium energy-trails fer dynamics and elucidate the mechanism of the nonexponential energy-transfer dynamics Caused by local dynamic heterogeneity and/or local environment relaxation.