Yoon So Hee, Chung Yeon Ji, Kim Myung Soo
Department of Chemistry, Seoul National University, Seoul, Korea.
J Am Soc Mass Spectrom. 2008 May;19(5):645-55. doi: 10.1016/j.jasms.2008.02.003. Epub 2008 Feb 23.
Time-evolution of product ion signals in ultraviolet photodissociation (UV-PD) of singly protonated peptides with an arginine at the N-terminus was investigated by using a tandem time-of-flight mass spectrometer equipped with a cell floated at high voltage. Observation of different time-evolution patterns for different product ion types--an apparently nonstatistical behavior--could be explained within the statistical framework by invoking consecutive formation of some product ions and broad internal energy distributions for precursor ions. a(n) + 1 and b(n) ions were taken as the primary product ions from this type of peptide ions. Spectral characteristics in post-source decay, UV-PD, and collisionally activated dissociation at low and high kinetic energies could be explained via rough statistical calculation of rate constants. Specifically, the striking characteristics in high-energy CAD and UV-PD--dominance of a(n) and d(n) formed via a(n) + 1--were not due to the peculiarity of the excitation processes themselves, but due to quenching of the b(n) channels caused by the presence of arginine.
使用配备有高压浮动池的串联飞行时间质谱仪，研究了N端带有精氨酸的单质子化肽在紫外光解离（UV-PD）中产物离子信号的时间演化。对于不同类型的产物离子观察到不同的时间演化模式——一种明显的非统计行为——可以在统计框架内通过调用一些产物离子的连续形成和前体离子的广泛内能分布来解释。a(n)+1和b(n)离子被视为这类肽离子的主要产物离子。通过速率常数的粗略统计计算，可以解释源后衰变、UV-PD以及低、高动能下碰撞激活解离中的光谱特征。具体而言，高能CAD和UV-PD中的显著特征——通过a(n)+1形成的a(n)和d(n)占主导——不是由于激发过程本身的特殊性，而是由于精氨酸的存在导致b(n)通道的猝灭。
