PROTEINS AND PEPTIDES IN THE GAS PHASE

这项研究的目标是增加我们对分子内相互作用和蛋白质-溶剂相互作用的基本了解，这些相互作用决定了蛋白质在溶液中的三维结构。这些信息是理解蛋白质折叠所必需的，也是根据蛋白质的氨基酸序列预测蛋白质构象所必需的。最终，这些知识将有助于设计蛋白质来执行特定的功能。拟议研究的具体目标是检查蛋白质离子和多肽离子在气相中的构象、展开过程和水合作用。气相研究的优点是可以将分子内相互作用和蛋白质-溶剂相互作用分开，并分别进行研究。在溶液中，存在复杂的相互作用混合物，它们不能分开。这里使用的方法是非常规的，但在气相和溶液相中，负责蛋白质三维结构的基本分子相互作用是相同的，因此气相研究的结果可以追溯到溶液环境。拟议的实验将利用生物医学质谱学的最新发展，使在气相中产生脱水蛋白质离子成为可能。将对一些蛋白质和合成肽进行研究，选择它们来检查关键问题，如气相中不同氨基酸的固有阿尔法螺旋倾向。气相构象将通过离子迁移率测量来检查。将实验结果与分子动力学模拟的预测进行比较，将有助于深入了解蛋白质的去折叠和重折叠过程，并检验用于模拟蛋白质的理论方法。有关蛋白质-溶剂相互作用的信息将从实验中获得，在气相中，将已知数量的水分子添加到脱水的蛋白质离子中。将进行与吸附单个水分子相关的热变和熵变化的测量，并检查被吸附的水分子如何改变蛋白质的结构。

The goal of the research described in this proposal is to increase our basic understanding of the intramolecular interactions and protein-solvent interactions that determine the three dimensional structure of proteins in solution. Such information is necessary to understand protein folding and needed to predict the conformation of a protein from its amino acid sequence. Ultimately, this knowledge will be useful in designing proteins to perform specific functions. The specific aims of the proposed research are to examine the conformations, unfolding processes, and hydration of protein ions and peptide ions in the gas phase. The advantage of gas phase studies is that it is possible to separate the intramolecular interactions and protein-solvent interactions, and study them individually. In solution, there is a complex mixture of interactions and they cannot be separated. The approach employed here is unconventional, but the fundamental molecular interactions responsible for the three-dimensional structure of a protein are the same in the gas phase and solution phase and so the results of the gas-phase studies can be related back to the solution environment. The proposed experiments will exploit the recent developments in biomedical mass spectrometry that make it possible to produce dehydrated protein ions in the gas phase. Studies will be performed for a number of proteins and synthetic peptides, selected to examine key issues, such as the intrinsic alpha-helix propensity of the different amino acids in the gas phase. The gas phase conformations will be examined by ion mobility measurements. Comparison of the experimental results with the predictions of molecular dynamics simulations will provide insight into the unfolding and refolding processes, and test the theoretical methods used to model proteins. Information about protein-solvent interactions will be obtained from experiments where a known number of water molecules are added to the dehydrated protein ions in the gas phase. Measurements of the enthalpy and entropy changes associated with adsorbing individual water molecules will be performed, along with an examination of how the adsorbed water molecules modify the structure of the protein.