Department of Physics, Applied Physics and Astronomy, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, 110 8th St., Troy, New York 12180, USA.
J Chem Phys. 2011 Mar 28;134(12):125101. doi: 10.1063/1.3558776.
The interactions of proteins with solid surfaces occur in a variety of situations. Motivated by the many nanoengineering applications of protein-carbon nanotube hybrids, we investigate the conformational transitions of hen egg white lysozyme adsorbed on a carbon nanotube. Using a C(α) structure-based model and replica exchange molecular dynamics, we show how the folding/unfolding equilibrium of the adsorbed protein varies with the strength of its coupling to the surface. The stability of the native state depends on the balance between the favorable entropy and unfavorable enthalpy change on adsorption. In the case of a weakly attractive surface when the former dominates, the protein is stabilized. In this regime, the protein can fold and unfold while maintaining the same binding fraction. With increasing surface attraction, the unfavorable enthalpic effect dominates, the native state is destabilized, and the protein has to extensively unbind before changing states from unfolded to folded. At the highest surface coupling, the entropic penalty of folding vanishes, and a folding intermediate is strongly stabilized. In this intermediate state, the α-domain of lysozyme is disrupted, while the β-sheet remains fully structured. We rationalize the relative stability of the two domains on the basis of the residue contact order.
蛋白质与固体表面的相互作用发生在各种情况下。受蛋白质-碳纳米管杂化许多纳米工程应用的启发，我们研究了吸附在碳纳米管上的鸡卵清溶菌酶的构象转变。使用基于 C(α)结构的模型和复制交换分子动力学，我们展示了吸附蛋白质的折叠/去折叠平衡如何随其与表面的耦合强度而变化。天然状态的稳定性取决于吸附时有利的熵变和不利的焓变之间的平衡。在表面吸引力较弱的情况下，当前者占主导地位时，蛋白质会稳定。在这个范围内，蛋白质可以折叠和展开，同时保持相同的结合分数。随着表面吸引力的增加，不利的焓效应占主导地位，天然状态被破坏，蛋白质必须在改变状态之前广泛解吸，从展开态变为折叠态。在最高的表面结合下，折叠的熵罚消失，折叠中间体得到强烈稳定。在这个中间状态下，溶菌酶的α-结构域被破坏，而β-折叠仍然完全结构。我们根据残基接触顺序来解释两个结构域的相对稳定性。
