Nanoconfinement Raises the Energy Barrier to Hydrogen Atom Exchange between Water and Glucose
Nanoconfinement Raises the Energy Barrier to Hydrogen Atom Exchange between Water and Glucose
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DOI：
10.1021/acs.jpcb.0c10681
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发表时间：
2021-03-30
影响因子：
3.3
通讯作者：
Levinger, Nancy E.
中科院分区：
文献类型：
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作者：
Miller, Samantha L.;Wiebenga-Sanford, Benjamin P.;Levinger, Nancy E.
在大量的水环境中，不稳定羟基之间的质子交换通常容易而迅速地发生。纳米限制可以极大地改变这个通常容易的过程。通过交换光谱（EXSY）核磁共振测量，我们观察到，在AOT（二（2-乙基己基）磺基琥珀酸钠）反胶束中，葡萄糖和水的纳米限制提高了不稳定氢交换的能量垒，这表明氢键网络被破坏。在接近室温的情况下，我们测量到足够高的屏障，可以将这一过程减缓2个数量级。虽然在这些纳米限制环境中，随着温度的降低，交换速率会减慢，但我们在285 K以下测量的势垒比在室温下测量的势垒低3-5倍，这表明该过程的机制发生了变化。这些发现表明，在惊人的高温阈值下，氢隧穿的可能性。此外，交换率的差异取决于葡萄糖吡喃糖环上羟基的位置，这表明葡萄糖在反胶束界面上的净取向。
In bulk aqueous environments, the exchange of protons between labile hydroxyl groups typically occurs easily and quickly. Nanoconfinement can dramatically change this normally facile process. Through exchange spectroscopy (EXSY) NMR measurements, we observe that nanoconfinement of glucose and water within AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles raises the energy barrier to labile hydrogen exchange, which suggests a disruption of the hydrogen bond network. Near room temperature, we measure barriers high enough to slow the process by as much as 2 orders of magnitude. Although exchange rates slow with decreasing temperatures in these nanoconfined environments, the barrier we measure below similar to 285 K is 3-5 times lower than the barrier measured at room temperature, indicating a change in mechanism for the process. These findings suggest the possibility of hydrogen tunneling at a surprisingly high-temperature threshold. Furthermore, differences in exchange rates depend on the hydroxyl group position on the glucose pyranose ring and suggest a net orientation of glucose at the reverse micelle interface.