确定蛋白质未折叠状态的能量学对于理解有序蛋白质的折叠机理和内在无序蛋白质的结构-功能关系至关重要。这里,我们采用线圈球跃迁理论来开发从单分子荧光共振能量转移谱中提取相互作用和自由能信息的一般方案。通过结合蛋白质稳定性数据,我们已经确定了许多系统中天然状态和最大塌陷变性状态之间的自由能差,提供有关蛋白质折叠中的特异性/非特异性相互作用的见解。证明了变性剂效应的转移和结合模型都解释了残基间相互作用对变性剂浓度的线性依赖性,因此在线圈-球跃迁理论下是相容的,以进一步确定未折叠状态的构象集合的尺寸和自由能。还讨论了缩放行为和有效θ状态。
Determining the energetics of the unfolded state of a protein is essential for understanding the folding mechanics of ordered proteins and the structure-function relation of intrinsically disordered proteins. Here, we adopt a coil-globule transition theory to develop a general scheme to extract interaction and free energy information from single-molecule fluorescence resonance energy transfer spectroscopy. By combining protein stability data, we have determined the free energy difference between the native state and the maximally collapsed denatured state in a number of systems, providing insight on the specific/nonspecific interactions in protein folding. Both the transfer and binding models of the denaturant effects are demonstrated to account for the revealed linear dependence of inter-residue interactions on the denaturant concentration, and are thus compatible under the coil-globule transition theory to further determine the dimension and free energy of the conformational ensemble of the unfolded state. The scaling behaviors and the effective θ-state are also discussed.