自洽简正模分析中蛋白质的动力学跃迁和低频模的非高斯行为
The dynamical transition in proteins and non-Gaussian behavior of low frequency modes in Self Consistent Normal Mode Analysis
摘要：
应用自洽正态模分析（SCNMA）方法研究了血红素c型细胞色素f蛋白质的温度依赖性运动。经典的简正模分析（NMA）假设谐振行为，蛋白质均方位移（MSD）与温度呈线性关系。这只与低温实验结果一致。为了将蛋白质在低温和生理温度之间的振动联系起来，我们在SCNMA中引入了一组拟合的非谐势。此外，量子谐振子（QHO）理论已被用来计算位移分布的各个振动模式。我们发现，涉及软键的模式在生理温度下表现出显着的非高斯动力学，这可能是弹性非相干中子散射（EINS）探测的蛋白质运动的非高斯行为的原因。在低频区（<50 cm ~（-1）或0.6ps），组合理论显示了由少数“扭转”模软化引起的动力学转变< 6meVor >。这些模式在加热时从高斯分布变为经典分布。我们的理论为理解蛋白质动力学转变的微观起源提供了另一种方法。
英文摘要：
Self Consistent Normal Mode Analysis (SCNMA) is applied to heme c type cytochrome f to study temperature dependent protein motion. Classical Normal Mode Analysis (NMA) assumes harmonic behavior and the protein Mean Square Displacement (MSD) has a linear dependence on temperature. This is only consistent with low temperature experimental results. To connect the protein vibrational motions between low temperature and physiological temperature, we have incorporated a fitted set of anharmonic potentials into SCNMA. In addition, Quantum Harmonic Oscillator (QHO) theory has been used to calculate the displacement distribution for individual vibrational modes. We find that the modes involving soft bonds exhibit significant non-Gaussian dynamics at physiological temperature, which suggests it may be the cause of the non-Gaussian behavior of the protein motions probed by Elastic Incoherent Neutron Scattering (EINS). The combined theory displays a dynamical transition caused by the softening of few "torsional" modes in the low frequency regime (< 50cm-1or < 6meVor > 0.6ps). These modes change from Gaussian to a classical distribution upon heating. Our theory provides an alternative way to understand the microscopic origin of the protein dynamical transition.
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