Binding of divalent cations to acetate: molecular simulations guided by Raman spectroscopy,Physical Chemistry Chemical Physics

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Binding of divalent cations to acetate: molecular simulations guided by Raman spectroscopy
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2020-10-10 , DOI: 10.1039/d0cp02987d
Denilson Mendes de Oliveira _{1,

2,

3,

4} , Samual R. Zukowski _{1,

2,

3,

4} , Vladimir Palivec _{5,

6,

7,

8,

9} , Jérôme Hénin _{10,

11,

12,

13,

14} , Hector Martinez-Seara _{5,

6,

7,

8,

9} , Dor Ben-Amotz _{1,

2,

3,

4} , Pavel Jungwirth _{5,

6,

7,

8,

9} , Elise Duboué-Dijon _{5,

6,

7,

8,

9}

Affiliation

In spite of the biological importance of the binding of Zn²⁺, Ca²⁺, and Mg²⁺ to the carboxylate group, cation–acetate binding affinities and binding modes remain actively debated. Here, we report the first use of Raman multivariate curve resolution (Raman-MCR) vibrational spectroscopy to obtain self-consistent free and bound metal acetate spectra and one-to-one binding constants, without the need to invoke any a priori assumptions regarding the shapes of the corresponding vibrational bands. The experimental results, combined with classical molecular dynamics simulations with a force field effectively accounting for electronic polarization via charge scaling and ab initio simulations, indicate that the measured binding constants pertain to direct (as opposed to water separated) ion pairing. The resulting binding constants do not scale with cation size, as the binding constant to Zn²⁺ is significantly larger than that to either Mg²⁺ or Ca²⁺, although Zn²⁺ and Mg²⁺ have similar radii that are about 25% smaller than Ca²⁺. Remaining uncertainties in the metal acetate binding free energies are linked to fundamental ambiguities associated with identifying the range of structures pertaining to non-covalently bound species.

中文翻译：

二价阳离子与乙酸盐的结合：拉曼光谱法指导的分子模拟

尽管Zn 2 ⁺，Ca ²⁺和Mg ²⁺与羧酸根的结合具有生物学重要性，但阳离子-乙酸根的结合亲和力和结合方式仍在积极争论。在这里，我们报告第一次使用拉曼多元曲线决议（拉曼MCR）振动光谱获取自洽的游离和结合金属醋酸盐光谱和一到一个结合常数，而无需调用任何先验有关的假设相应的振动带的形状。实验结果与经典分子动力学模拟结合在一起，力场有效地解释了通过电荷缩放和从头算起的电子极化模拟表明，测得的结合常数与直接离子配对有关（与水分离相反）。尽管Zn ²⁺和Mg ²⁺具有相似的半径（大约25％），但与Zn ²⁺的结合常数明显大于与Mg ²⁺或Ca ²⁺的结合常数，因此所得的结合常数不会随阳离子的大小而变化。小于Ca ²⁺。金属乙酸盐结合自由能的剩余不确定性与确定与非共价结合物种有关的结构范围有关的基本模糊性有关。

更新日期：2020-10-20

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