Sultan Anas M, Hughes Zak E, Walsh Tiffany R
Institute for Frontier Materials, Deakin University, Waurn Ponds, Victoria 3216, Australia.
Biointerphases. 2018 Aug 31;13(6):06D403. doi: 10.1116/1.5046531.
How the presence of Ca ions at the aqueous TiO interface influences the binding modes of two experimentally identified titania-binding peptides, Ti-1 and Ti-2, is investigated using replica exchange with solute tempering molecular dynamics simulations. The findings are compared with available experimental data, and the results are contrasted with those obtained under NaCl solution conditions. For Ti-1, Ca ions enhance the adsorption of the negatively charged Asp8 residue in this sequence to the negatively charged surface, via Asp–Ca–TiO bridging. This appears to generate a nonlocal impact on the adsorption of Lys12 in Ti-1, which then pins the peptide to the surface via direct surface contact. For Ti-2, fewer residues were predicted to adsorb directly to the surface in CaCl, compared with predictions made for NaCl solution, possibly due to competition between the other peptide residues and Ca ions to adsorb to the surface. This reduction in direct surface contact gives rise to a more extensive solvent-mediated contact for Ti-2. In general, the presence of Ca ions resulted in a loss of conformational diversity of the surface-adsorbed conformational ensembles of these peptides, compared to counterpart data predicted for NaCl solution. The findings provide initial insights into how peptide–TiO interactions might be tuned at the molecular level via modification of the salt composition of the liquid medium.
利用溶质回火分子动力学模拟的副本交换方法，研究了水相TiO界面处Ca离子的存在如何影响两种实验鉴定的二氧化钛结合肽Ti-1和Ti-2的结合模式。将这些发现与现有的实验数据进行比较，并将结果与在NaCl溶液条件下获得的结果进行对比。对于Ti-1，Ca离子通过Asp–Ca–TiO桥连增强了该序列中带负电荷的Asp8残基对带负电荷表面的吸附。这似乎对Ti-1中Lys12的吸附产生了非局部影响，然后通过直接表面接触将肽固定在表面上。对于Ti-2，与NaCl溶液的预测相比，预计在CaCl中直接吸附到表面的残基较少，这可能是由于其他肽残基与Ca离子之间存在吸附到表面的竞争。这种直接表面接触的减少导致Ti-2有更广泛的溶剂介导接触。总体而言，与NaCl溶液预测的对应数据相比，Ca离子的存在导致这些肽的表面吸附构象集合的构象多样性丧失。这些发现为如何通过改变液体介质的盐组成在分子水平上调节肽与TiO的相互作用提供了初步见解。
