Stadler Andreas M, Koza Michael Marek, Fitter Jörg
Jülich Centre for Neutron Science JCNS and Institute for Complex Systems ICS, Forschungszentrum Jülich GmbH , 52425 Jülich, Germany.
J Phys Chem B. 2015 Jan 8;119(1):72-82. doi: 10.1021/jp509732q. Epub 2014 Dec 22.
Holo- and apomyoglobin can be stabilized in native folded, partially folded molten globules (MGs) and denatured states depending on the solvent composition. Although the protein has been studied as a model system in the field of protein folding, little is known about the internal dynamics of the different structural conformations on the picosecond time scale. In a comparative experimental study we investigated the correlation between protein folding and dynamics on the picosecond time scale using incoherent quasielastic neutron scattering (QENS). The measured mean square displacements (MSDs) of conformational motions depend significantly on the secondary structure content of the protein, whereas the correlation times of the observed internal dynamics were found to be similar irrespective of the degree of folding. The conformational entropy difference ΔSconf between the folded conformations and the acid denatured state could be determined from the measured MSDs and was compared to the entropy difference ΔS obtained from thermodynamic parameters reported in the literature. The observed difference between ΔS and ΔSconf was attributed to the entropy difference ΔShydr of dynamically disordered water molecules of the hydration shell. The entropy content of the hydration water is significantly larger in the native folded proteins than in the partially folded MGs. We demonstrate the potential of incoherent neutron scattering for the investigation of the role of conformational dynamics in protein folding.
全肌红蛋白和脱辅基肌红蛋白可以根据溶剂组成稳定在天然折叠、部分折叠的熔球态（MGs）和变性状态。尽管该蛋白质已作为蛋白质折叠领域的模型系统进行了研究，但在皮秒时间尺度上，对于不同结构构象的内部动力学却知之甚少。在一项对比实验研究中，我们使用非相干准弹性中子散射（QENS）研究了皮秒时间尺度上蛋白质折叠与动力学之间的相关性。所测量的构象运动的均方位移（MSD）显著取决于蛋白质的二级结构含量，而观察到的内部动力学的相关时间无论折叠程度如何都相似。折叠构象与酸变性状态之间的构象熵差ΔSconf可以从测量的MSD中确定，并与从文献报道的热力学参数获得的熵差ΔS进行比较。观察到的ΔS与ΔSconf之间的差异归因于水合壳层中动态无序水分子的熵差ΔShydr。天然折叠蛋白质中水合水的熵含量明显大于部分折叠的MGs。我们展示了非相干中子散射在研究构象动力学在蛋白质折叠中的作用方面的潜力。
