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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Thermodynamic Signatures of the Origin of Anti-Hofmeister Selectivity for Phosphate at Aqueous Interfaces
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Thermodynamic Signatures of the Origin of Anti-Hofmeister Selectivity for Phosphate at Aqueous Interfaces

机译：水性界面磷酸盐抗Hofmeister选择性起源的热力学签名

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摘要

The selectivities and driving forces governing phosphate recognition by charged receptors at prevalent aqueous interfaces is unexplored relative to the many studies in homogeneous solutions. Here we report on electrostatic binding versus hydrogen-bond-assisted electrostatic binding of phosphate (H2PO4-) for two important receptor classes in the unique microenvironment of the air-water interface. We find that the methylated ammonium receptor (U-Ammo(+)) is dominated by electrostatic binding to phosphate anions and fails to be selective for phosphate binding over chloride, whereas the highly phosphateselective guanidinium receptor (U-Guan(+)) provides synergistic hydrogen-bonding and electrostatic interactions. Apparent binding constants were evaluated in situ for U-Ammo(+) and U-Guan(+) using temperature-controlled infrared reflection-absorption spectroscopy with Langmuir-type fitting. Thermodynamic quantities showed enthalpically driven binding affinities of U-Guan(+) and U-Ammo(+) receptors (Delta H degrees(b) = -71 (+/- 9) kJ/mol and Delta H degrees(b) = -155 (+/- 13) kJ/mol, respectively). U-Guan(+) revealed a nearly fourfold smaller entropic barrier to binding (Delta S degrees(b) = -132 (+/- 34) J/mol K) than the U-Ammo(+) receptor (Delta S degrees(b) = -440 (+/- 45) J/mol K), attributed to hydration differences. The larger entropic penalty for the U-Ammo(+) receptor is correlated with a molecular expansion shown in surface pressure-area isotherms, whereas the smaller entropic penalty of the U-Guan(+) receptor conversely correlated with no expansion. The U-Guan(+) receptor also revealed anti-Hofmeister selectivity for phosphate over chloride, while the non-hydrogenbonding U-Ammo(+) receptor followed Hofmeister selectivity. Our results indicate that hydrogen bonding is an integral chemical design element for achieving anti-Hofmeister selectivity for phosphate.
机译：通过在普遍的含水界面上的带电受体的选择性和驱动力，相对于均质溶液中的许多研究是未探究的。在这里，我们报道了在空气界面的独特微环境中的两个重要受体类的磷酸盐（H2PO4-）的静电结合与氢键辅助静电结合。我们发现甲基化铵受体（U-Ammo（+））通过与磷酸根阴离子的静电结合来支配，并且不能为磷酸盐结合选择性，而高磷酸盐胍受体（U-GUAN（+））提供协同作用氢键和静电相互作用。使用温度控制的红外反射吸收光谱与Langmuir型配件原位评估表观结合常数。使用温度控制的红外反射吸收光谱法评价U-Ammo（+）和U-Guan（+）。热力学量显示U-GUAN（+）和U-AMMO（+）受体的焓驱动的结合亲和力（DELTA H度（B）= -71（+/- 9）KJ / mol和DELTA H度（B）= - 155（+/- 13）kj / mol，分别）。 U-GUAN（+）揭示了与U-AMMO（+）受体（三角形）（ΔS度）的结合的近倍熵势垒（δS度（b）= -132（+/- 34）j / mol k）（ b）= -440（+/- 45）j / mol k），归因于水合差异。 u-ammo（+）受体的较大熵罚分与表面压力区域等温线中所示的分子膨胀相关，而U-guan（+）受体的熵较小罚球与没有扩张相反。 U-Guan（+）受体还揭示了抗磷酸盐抗Hofmeister选择性，而非氢化U-Ammo（+）受体遵循HofMeister选择性。我们的结果表明，氢键是一种用于实现磷酸盐的抗HofMeister选择性的整体化学设计元件。

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