PROTEINS AND PEPTIDES IN THE GAS PHASE

在这个建议中描述的研究的目标是增加我们的分子内相互作用和蛋白质-溶剂的相互作用，确定在溶液中的蛋白质的三维结构的基本理解。 这些信息对于理解蛋白质折叠是必要的，并且需要从其氨基酸序列预测蛋白质的构象。 最终，这些知识将有助于设计蛋白质以执行特定功能。 所提出的研究的具体目标是检查的构象，展开过程中，和水合的蛋白质离子和肽离子在气相中。 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，并单独研究它们。 在溶液中，存在相互作用的复杂混合物，并且它们不能被分离。 这里采用的方法是非常规的，但负责蛋白质三维结构的基本分子相互作用在气相和溶液相中是相同的，因此气相研究的结果可以与溶液环境相关。 拟议的实验将利用生物医学质谱的最新发展，使其有可能在气相中产生脱水蛋白质离子。将对一些蛋白质和合成肽进行研究，选择这些蛋白质和合成肽来研究关键问题，例如气相中不同氨基酸的固有α-螺旋倾向。 将通过离子迁移率测量来检查气相构象。 将实验结果与分子动力学模拟的预测进行比较，将深入了解展开和重折叠过程，并测试用于模拟蛋白质的理论方法。 关于蛋白质-溶剂相互作用的信息将从实验中获得，其中已知数量的水分子被添加到气相中的脱水蛋白质离子中。 将进行与吸附单个水分子相关的焓变和熵变的测量，沿着检查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.