Department of Chemical Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India.
Biochemistry. 2011 Jan 25;50(3):397-408. doi: 10.1021/bi101440c. Epub 2010 Dec 29.
Protein function is intimately related to the dynamics of the protein as well as to the dynamics of the solvent shell around the protein. Although it has been argued extensively that protein dynamics is slaved to solvent dynamics, experimental support for this hypothesis is scanty. In this study, measurements of fluorescence anisotropy decay kinetics have been used to determine the motional dynamics of the fluorophore acrylodan linked to several locations in a small protein barstar in its various structural forms, including the native and unfolded states as well as the acid and protofibril forms. Fluorescence upconversion and streak camera measurements have been used to determine the solvation dynamics around the fluorophore. Both the motional dynamics and solvent dynamics were found to be dependent upon the location of the probe as well as on the structural form of the protein. While the (internal) motional dynamics of the fluorophore occur in the 0.1-3 ns time domain, the observed mean solvent relaxation times are in the range of 20-300 ps. A strong positive correlation between these two dynamical modes was found in spite of the significant difference in their time scales. This observed correlation is a strong indicator of the coupling between solvent dynamics and the dynamics in the protein.
蛋白质的功能与蛋白质的动力学以及蛋白质周围溶剂壳的动力学密切相关。尽管已经广泛争论说蛋白质动力学受制于溶剂动力学，但对该假说的实验支持却很少。在这项研究中，使用荧光各向异性衰减动力学测量来确定在其各种结构形式（包括天然状态和展开状态以及酸形式和原纤维形式）中的小蛋白 barstar 中连接到几个位置的荧光团 acrylodan 的运动动力学。使用荧光上转换和条纹相机测量来确定荧光团周围的溶剂动力学。发现运动动力学和溶剂动力学都取决于探针的位置以及蛋白质的结构形式。虽然荧光团的（内部）运动动力学发生在 0.1-3ns 的时间范围内，但观察到的平均溶剂弛豫时间在 20-300ps 的范围内。尽管它们的时间尺度有很大差异，但在这两种动力学模式之间发现了强烈的正相关。这种观察到的相关性是溶剂动力学与蛋白质动力学之间耦合的有力指标。
