Hilderbrand Amy E, Myung Sunnie, Barnes Catherine A Srebalus, Clemmer David E
Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA.
J Am Soc Mass Spectrom. 2003 Dec;14(12):1424-36. doi: 10.1016/j.jasms.2003.08.002.
Recent improvements in ion mobility/time-of-flight mass spectrometry techniques have made it possible to incorporate nano-flow liquid chromatography and collision induced dissociation techniques. This combination of approaches provides a new strategy for detailed characterization of complex systems--such as, combinatorial libraries. Our work uses this technology to provide a detailed analysis of a tetrapeptide library having the general form Xxx1-Xxx2-Xxx3-Xxx4 where Xxx1 = Glu, Phe, Val, Asn; Xxx2 = Glu, Phe, Val, Tyr; Xxx3 = Glu, Phe, Val, Thr; and Xxx4 = Glu, Phe, Val, Leu--a system that is expected to contain 256 different peptide sequences. The results corroborate the presence of many expected peptide sequences and indicate that some synthetic steps appear to have failed. Particularly interesting is the observation of a t-butyl protecting group on the tyrosine (Tyr) residue. It appears that most Tyr containing peptides that have this t-butyl group attached favor formation of [2M + 2H]2+ dimers, which can be readily distinguished from [M + H]+ monomers based on differences in their gas-phase mobilities. In this case, we demonstrate the use of the mobility differences between [2M + 2H]2+ and [M + H]+ ions as a signature for a failure of a synthetic step.
离子淌度/飞行时间质谱技术最近的改进使得纳入纳流液相色谱和碰撞诱导解离技术成为可能。这种方法的结合为详细表征复杂系统（如组合文库）提供了一种新策略。我们的工作利用这项技术对一个具有通用形式Xxx1-Xxx2-Xxx3-Xxx4的四肽文库进行了详细分析，其中Xxx1 = 谷氨酸、苯丙氨酸、缬氨酸、天冬酰胺；Xxx2 = 谷氨酸、苯丙氨酸、缬氨酸、酪氨酸；Xxx3 = 谷氨酸、苯丙氨酸、缬氨酸、苏氨酸；Xxx4 = 谷氨酸、苯丙氨酸、缬氨酸、亮氨酸——预计该系统包含256种不同的肽序列。结果证实了许多预期肽序列的存在，并表明一些合成步骤似乎失败了。特别有趣的是在酪氨酸（Tyr）残基上观察到叔丁基保护基。似乎大多数带有这种叔丁基的含酪氨酸肽有利于形成[2M + 2H]2+二聚体，基于它们气相淌度的差异，可以很容易地将其与[M + H]+单体区分开来。在这种情况下，我们证明了利用[2M + 2H]2+和[M + H]+离子之间的淌度差异作为合成步骤失败的特征。
