MASS SPECTRAL STUDIES OF DEPROTONATED PEPTIDES

这项研究的目标是开发分析程序 用负离子质谱仪测定酸性多肽的含量。许多生物 用于疾病治疗的多肽和多肽含有大量的谷氨酸 或天冬氨酸残基；其他含有酸性磷酸盐或硫酸盐 组。在过去的15年里，质谱学的进步 使其成为测定分子质量的一种选择方法 多肽序列。数以百计的报告已经出现在这两个人身上 带正电的质子化肽的质谱学研究 离子。相比之下，相对较少的研究集中在负面-- 带电的、去质子化的离子，这些研究中的大多数都涉及 单电荷离子含有四个或更少残基的。然而， 酸性多肽通常更容易形成负离子而不是正离子。 离子。 该项目将大量使用两种先进的方法 光谱：电喷雾电离傅里叶变换离子回旋加速器 共振(ESI/FT-ICR)和基质辅助激光解吸电离 飞行时间(MALDI/TOF)。ESI/FT-ICR研究将涉及低能量 多重去质子化离子的碰撞诱导解离(CID)， 而MALDI/TOF工作将在单个上使用震源后衰减(PSD 去质子离子。主要目的是阐明解离。 机械装置。不同类型氨基酸引起的碎裂 将探索残基及其序列。结构特征 正在调查的包括谷氨酸和天冬氨酸残留物，非 酸性残基，如脯氨酸和赖氨酸，C-末端端基(-OH 或NH2)、高度酸性的磷酸盐和硫酸盐基团以及相互作用 介于酸性残基和碱性残基之间。对于倍数去质子化离子 由ESI产生的离子电荷的数量和位置(因此 库仑斥力的大小)必须加以考虑。分子 将执行动力学计算以深入了解库仑 能量和构象，这可以影响解离。网络的影响 将通过改变父代来评估碎裂的内部能量 FT-ICR和TOF中的离子激发能，通过增加PSD 在离子离开源之后发生碰撞。负离子 解离将与相应的正值进行比较。 离子。此外，影响负离子的结构性因素 将对生产进行调查。通过以下方法提高去质子化离子的产额 MALDI，将开发用于多肽的基本矩阵。

The objective of this research is to develop procedures for the analysis of acidic peptides by negative ion mass spectrometry. Many biological peptides and peptides used in disease treatment have numerous glutamic or aspartic acid residues; others contain acidic phosphate or sulfate groups. In the past fifteen years, advances in mass spectrometry have made it a method of choice for determining the molecular masses and sequences of peptides. Hundreds of reports have appeared on the tandem mass spectrometry (MS/MS) of positively-charged, protonated peptide ions. In contrast, relatively little work has focused on negatively- charged, deprotonated ions and the majority of these studies have dealt with singly charged ions containing four or fewer residues. However, acidic peptides often form negative ions more readily than positive ions. This project will utilize two advancing methodologies in mass spectrometry: electrospray ionization Fourier transform ion cyclotron resonance (ESI/FT-ICR) and matrix-assisted laser desorption ionization time-of-flight (MALDI/TOF). ESI/FT-ICR studies will involve low-energy collision-induced dissociation (CID) on multiply deprotonated ions, while MALDI/TOF work will employ post-source decay (PSD) on singly deprotonated ions. The major aim is to elucidate dissociation mechanisms. Fragmentations induced by various types of amino acid residues and by their sequences will be explored. Structural features under investigation include glutamic and aspartic acid residue, non- acidic residues such a proline and lysine, the C-terminal endgroup (-OH or NH2), highly acidic phosphate and sulfate groups, and interactions between acidic and basic residues. For multiply deprotonated ions generated by ESI, the number and locations of ionic charges (and thus the magnitude of Coulomb repulsion) must be considered. Molecular dynamics calculations will be performed to gain insight into Coulomb energy and conformations, which can affect dissociation. The impact of internal energy on fragmentation will be assessed by varying the parent ion excitation energy in the FT-ICR and, in the TOF, by augmenting PSD with collisions occurring after ions leave the source. Negative ion dissociation will be compared to that of the corresponding positive ions. In addition, structural factors that influence negative ion production will be investigated. To enhance deprotonated ion yields by MALDI, basic matrices will be developed for peptides.