Are disulfide bonds resilient to double ionization? Insights from coincidence spectroscopy and ab initio calculations,RSC Advances

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Are disulfide bonds resilient to double ionization? Insights from coincidence spectroscopy and ab initio calculations
RSC Advances ( IF 3.9 ) Pub Date : 2020-9-22 , DOI: 10.1039/d0ra05979j
Lautaro R Varas ₁ , Felipe Fantuzzi _{2,

3,

4} , Lúcia Helena Coutinho ₅ , Rafael B Bernini ₆ , Marco Antonio Chaer Nascimento ₂ , G G B de Souza ₂

Affiliation

Disulfide bonds (–S–S–) are commonly present in biomolecules and have also been detected in astrophysical environments. In this work, the stability of the disulfide bond towards double ionization is investigated using quantum chemical calculations and photoelectron photoion photoion coincidence (PEPIPICO) spectroscopy measurements on the prototype dimethyl disulfide (CH₃SSCH₃, DMDS) molecule. The experiments were performed using high energy synchrotron radiation photons before (2465.0 eV) and at (2470.9 eV) the first sigma resonance around the S 1s edge. We applied the multivariate normal distribution analysis to identify the most plausible ionic fragmentation mechanisms from the doubly ionized DMDS. By mapping the minimum energy structures on the dicationic C₂H₆S₂²⁺ potential energy surface, we show that disulfide bonds are only present in high-lying isomers, in contrast to their analogous neutral systems. Our results also indicate that the number of fragment ions containing a disulfide bond for both photon energies is negligible. Taken together, our results reveal that the disulfide bond is severely damaged as a consequence of sulfur core–shell ionization processes, due to the lowering of its thermodynamic stability in multiply-charged systems.

中文翻译：

二硫键对双电离有弹性吗？符合光谱和从头计算的见解

二硫键（-S-S-）通常存在于生物分子中，并且也在天体物理环境中被检测到。在这项工作中，使用量子化学计算和对原型二甲基二硫醚（CH ₃ SSCH ₃ ，DMDS）分子的光电子光电子符合（PEPIPICO）光谱测量来研究二硫键对双电离的稳定性。实验是在 S 1s 边缘周围第一次西格玛共振之前 (2465.0 eV) 和 (2470.9 eV) 使用高能同步辐射光子进行的。我们应用多元正态分布分析来识别双电离 DMDS 中最合理的离子碎片机制。通过绘制双离子 C ₂ H ₆ S ₂ ²⁺势能表面上的最小能量结构，我们发现二硫键仅存在于高位异构体中，与其类似的中性系统相反。我们的结果还表明，对于两种光子能量来说，含有二硫键的碎片离子的数量可以忽略不计。综上所述，我们的结果表明，硫核壳电离过程导致二硫键严重受损，这是由于多电荷系统中热力学稳定性的降低。

更新日期：2020-09-22

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