Wang Bing, Yu Jiayi, Wang Huixin, Wei Zhonglin, Guo Xinhua, Xiao Zhaohui, Zeng Zhoufang, Kong Wei
College of Chemistry, Jilin University, Changchun, 130012, China.
J Am Soc Mass Spectrom. 2014 Dec;25(12):2116-24. doi: 10.1007/s13361-014-0994-9. Epub 2014 Oct 4.
An N-terminal deuterohemin-containing hexapeptide (DhHP-6) was designed as a short peptide cytochrome c (Cyt c) mimetic to study the effect of N-terminal charge on peptide fragmentation pathways. This peptide gave different dissociation patterns than normal tryptic peptides. Upon collision-induced dissociation (CID) with an ion trap mass spectrometer, the singly charged peptide ion containing no added proton generated abundant and characteristic bn-44 ions instead of bn-28 (an) ions. Studies by high resolution mass spectrometry (HRMS) and isotope labeling indicate that elimination of 44 Da fragments from b ions occurs via two different pathways: (1) loss of CH3CHO (44.0262) from a Thr side chain; (2) loss of CO2 (43.9898) from the oxazolone structure in the C-terminus. A series of analogues were designed and analyzed. The experimental results combined with Density Functional Theory (DFT) calculations on the proton affinity of the deuteroporphyrin demonstrate that the production of these novel bn-44 ions is related to the N-terminal charge via a charge-remote rather than radical-directed fragmentation pathway.
设计了一种含N端血红素的六肽（DhHP-6）作为短肽细胞色素c（Cyt c）模拟物，以研究N端电荷对肽片段化途径的影响。该肽产生的解离模式与正常胰蛋白酶肽不同。在离子阱质谱仪上进行碰撞诱导解离（CID）时，未添加质子的单电荷肽离子产生了丰富且特征性的bn-44离子，而不是bn-28（an）离子。高分辨率质谱（HRMS）和同位素标记研究表明，从b离子中消除44 Da片段有两种不同途径：（1）从苏氨酸侧链失去CH3CHO（44.0262）；（2）从C端恶唑酮结构失去CO2（43.9898）。设计并分析了一系列类似物。实验结果与对原卟啉质子亲和力的密度泛函理论（DFT）计算相结合，表明这些新型bn-44离子的产生是通过电荷远程而非自由基导向的片段化途径与N端电荷相关。
