Cooperative hydrophobe aggregation mediated by interfacially active alcohols
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- 作者：Ashish V. Sangwai ; Luigi P. Verdoni ; Henry S. Ashbaugh ; hanka@tulane.edu" class="auth_mail" title="E-mail the corresponding author
- 关键词：Hydrophobic interactions ; Aqueous solutions
- 刊名：Fluid Phase Equilibria
- 出版年：2016
- 出版时间：15 January 2016
- 年：2016
- 卷：407
- 期：Complete
- 页码：255-261
- 全文大小：1743 K
文摘
The aggregation of isobutane and toluene in aqueous solutions of 5 wt% alcohols of varying polarity is studied using molecular dynamic simulations. In the absence of alcohol these hydrophobes are predominantly monomeric in water with minimal clustering. Simple alcohols like methanol and ethanol barely perturb the hydrophobe cluster size distribution. More complex alcohols with added carbon and hydroxyl units, on the other hand, can induce cooperative aggregation of the hydrophobic solutes and alcohols, with mean cluster sizes greater than that observed for the hydrophobes or alcohols alone. The tendency for an alcohol to induce cooperative aggregation is strongly correlated with its affinity for sitting at an oil/water interface, as quantified by the free energy of transferring a single alcohol molecule from bulk water to a water/octane interface. The onset of aggregation occurs over a narrow range of adsorption free energies centered about −3.2 kcal/mol. Alcohols with adsorption free energies below this value tend to promote hydrophobic aggregation, and alcohols with adsorption free energies above this value are indifferent to aggregation. The tendency for alcohols to induce hydrophobic aggregation is also correlated with their tendency to lower the size selective barrier to transport of cargo greater than ∼30 kDa in mass across the nuclear pore complex in eukaryotic cells, which regulates traffic between the nucleus and cytoplasm. The transport barrier within the central channel of the nuclear pore complex is composed of tangled natively unfolded proteins with repeat sequences rich in leucine and phenyalanine, which isobutane and toluene are side chain analogs of. Our results suggest interfacial active alcohols promote leucine and phenyalanine aggregation, subsequently opening holes within the nuclear pore complex’s transport barrier to provide alternate routes for cargo translocation.