Dynamics of molecules and ions in the gas phase

该提案涉及的项目包括研究离子在气相中的运动方式，以及如何利用这种运动的动力学来获得关于离子结构的信息，或者在太空中操纵它。一个主要的主题是研究蛋白质复合体形成的离子。许多实验表明，这些复合体在气相中分解成具有不寻常电荷分布的碎片。具体地说，电荷并不像人们预期的那样在碎片之间对称分布。有趣的问题是，“为什么会发生这种情况？”流行的机制表明，在裂解过程中，复合体中的一些蛋白质开始展开，这导致电荷分布变得不对称。我们的目标是使用运行分子动力学代码的计算机来模拟这些过程，试图详细了解这种机制，并对其进行控制。这种机制的一个重要部分是质子在离子不同部分之间的转移。在气相中，质子的移动方式可能与在溶液中非常不同。然而，了解质子转移对于质谱仪来说非常重要，他们目前正在使用这些气相物种来对氨基酸进行排序从而识别存在于细胞或其他生物样本中的蛋白质。第二个主要主题是分离不同形状的离子。这个想法是开发一种方法，优先将非球形离子从球形离子中分离出来。对于分析和研究环境中化学物质反应的气溶胶和大气科学家来说，这种技术将非常强大。同样，我们希望开发一种方法来对准气相中的离子，以帮助探索气相物种的反应性和行为的实验。

The proposal involves projects that study the way ions move in the gas phase, and how the dynamics of this motion can be used to gain information about the structure of an ion, or to manipulate it in space. One major theme examines ions formed from protein complexes.  Experiments have shown that these complexes, in the gas phase, break up into pieces that have unusual charge distributions.  Specifically, the charges do not spread symmetrically among the pieces, as one would expect. The interesting question is, "Why does this happen?". The prevailing mechanism suggests that some proteins in the complex begin to unfold during the break up, and this causes the charge distributions to become asymmetric.  Our goal is to simulate these processes using computers running molecular dynamics codes, in an attempt to understand this mechanism in detail, and to control it.  One important part of this mechanism is the transfer of protons between different parts of the ion.  In the gas phase, the way protons move can be very different than in solution.  However, understanding proton transfer is very important for mass spectrometrists, who currently are using these gas phase species to sequence amino acids, and thus identify the proteins that exist in a cell or other biological sample. A second major theme is concerned with separating ions with different shapes.  The idea is to develop methods that will preferentially separate ions with non-spherical shapes from those that are spherical.  Such a technique would be very powerful for aerosol and atmospheric scientists, who analyze and study the reactions of chemicals in the environment.  Along the same lines, we would like to develop a method to align ions in the gas phase, to aid experiments that probe the reactivity and behaviour of gas phase species.