在气相中,d ((GCGAAGC) 是否保留了针头结构? 一个周期性离子运动质谱和密度功能理论计算研究
Jiahao Wan1, Marianna Nytka2,3, Haocheng Qian1
1Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States.
这项研究揭示了最小的寡核酸d ((GCGAAGC) 和其异构体在气相中采用紧的非毛结构,挑战了以前关于它们的构造和解离路径的假设.
科学领域:
- 质谱测量质量谱测量
- 计算化学计算化学
- 橄核酸的化学成分
背景情况:
- d ((GCGAAGC) 是已知的最小的寡核酸,因其溶液中的发针结构而闻名.
- 了解寡核酸气相结构对于解释质谱数据至关重要.
研究的目的:
- 研究多质子d ((GCGAAGC) 和其异构体的气相结构和解离机制.
- 为了进行结构阐明,将实验结果与理论计算进行比较.
主要方法:
- 电子喷雾电离 (ESI) 与循环离子移动性光谱学 (c-IMS) 相结合.
- 波恩-奥本海默分子动力学 (BOMD) 和密度函数理论 (DFT) 的计算.
- 碰撞诱导解离 (CID) 和电子转移-CID (ET-CID) 串联质谱.
主要成果:
- 观察到d(GCGAAGC) 滴定和三滴定的多个对应体和原体,其碰撞横截面 (CCS) 范围为439481 Å2.
- DFT的计算表明,紧的,扭曲的形结构的能量比d(GCGAAGC) 2+的发针结构要低.
- 低能量的d ((GCGAAGC) 4+离子是zwitterionic,所有的purin基都是质子化的,电荷由酸离子平衡.
- 实验中的CCS值与MobCal-MPI计算非常相匹配.
- CID和ET-CID揭示了核基损失和骨干裂,主要是在终端核酸.
结论:
- d ((GCGAAGC) 和其异构体的气相结构主要是紧的和非毛的,与它们的溶液状态结构有很大的不同.
- 质子化导致基对的破坏和zwitterionic图案的形成,稳定较低能量的 conformers.
- 理论计算对于解释实验性离子流动性和寡核酸的解离数据至关重要.
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