在从聚乙烯I过渡到聚乙烯II的过程中,使用离子移动性光谱法-质谱法对中间体进行表征
Liuqing Shi1, Alison E Holliday, Huilin Shi
1Department of Chemistry, Indiana University , 800 Kirkwood Avenue, Bloomington, Indiana 47405, United States.
Journal of the American Chemical Society
|August 9, 2014
概括
在溶液中,聚烯可以在螺旋结构 (PPI 和 PPII) 之间过渡. 离子流动性光谱-质谱在这种结构转换过程中揭示了连续的cis-trans异构和并行路径.
科学领域:
- 生物物理化学 生物物理化学
- 质谱测量质量谱测量
- 结构生物学 结构生物学
背景情况:
- 聚烯采用不同的螺旋结构,聚烯I (PPI,全cis) 在酒精中,聚烯II (PPII,全trans) 在水中.
- 之前的离子移动性光谱-质谱 (IMS-MS) 研究将气相形状与溶液相PPI和PPII螺旋相联系起来.
研究的目的:
- 在使用IMS-MS进行溶剂交换期间,研究PPI转化为PPII螺旋的Polyproline-13 (Pro13) 转化过程中的中间步骤和机制.
- 阐明结构动力学和控制聚烯在水性环境中的螺旋转变的途径.
主要方法:
- 使用离子移动性光谱-质谱 (IMS-MS) 来分析不同过渡时间的Pro13离子 ([M + 2H](2+)).
- 测量了碰撞横截面分布,以确定符合性.
- 使用温度依赖研究和分子动力学模拟来确定激活参数和中间结构.
主要成果:
- 在Pro13过渡期间,确定了两种主要适应者,PPI和PPII螺旋,以及六种中间亚群.
- 提出了一个过渡机制,涉及连续的cis-trans异体化,其次是并行过程.
- 取决于温度的研究产生了Arrhenius激活参数,分子动力学模拟提供了对中间结构的洞察,表明了连续的N端翻转,随后是中央或并行过渡.
结论:
- 这项研究揭示了聚烯在水溶液中的PPI到PPII螺旋转变的复杂,多步骤机制.
- 在过渡过程中发现了稳定的聚烯子群和明显的中间结构的证据.
- 这些发现为聚乙烯的结构可塑性及其构造动态提供了新的见解.
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