Jellen Emily E, Ryzhov Victor
Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL 60115, USA.
Eur J Mass Spectrom (Chichester). 2005;11(1):65-72. doi: 10.1255/ejms.704.
The stability and structure of non-covalent complexes of various peptides contatining basic amino acid residues (Arg, Lys) with metalloporphyrins were studied in a quadrupole ion trap mass spectrometer. The complexes of heme and three other metalloporphyrins with a variety of basic peptides and model systems were formed via electrospray ionization (ESI) and their stability was probed by energy-variable collision-induced dissociation (CID). A linear dependence for basic peptides and model compounds/metalloporphyrin complexes was observed in the plots of stability versus degrees of freedom and was used to evaluate relative bond strength. These results were then compared with previous data obtained for complexes of metalloporphyrins with His-containing peptides and peptides containing no basic amino acids. The binding strengths of Lys-containing peptide complexes in the gas phase was found to be almost as strong as that of Arg-containing complexes. Both systems showed stronger binding than His- containing peptides studied previously. To probe the structure of Arg and Lys non-covalent complexes (charge solvation versus salt bridges), two techniques, CID and ionmolecule reactions, were used. CID experiments indicate that the gas-phase complexes are most likely formed by charge solvation of the central metal ion in the metalloporphyrin by basic side chains of Arg or Lys. Results from the ionmolecule reaction studies are consistent with the charge solvation structure as well.
在四极杆离子阱质谱仪中研究了各种含有碱性氨基酸残基（精氨酸、赖氨酸）的肽与金属卟啉的非共价复合物的稳定性和结构。通过电喷雾电离（ESI）形成了血红素和其他三种金属卟啉与各种碱性肽及模型体系的复合物，并通过能量可变碰撞诱导解离（CID）探究了它们的稳定性。在稳定性与自由度的关系图中观察到碱性肽和模型化合物/金属卟啉复合物呈线性关系，并用于评估相对键强度。然后将这些结果与先前获得的金属卟啉与含组氨酸肽及不含碱性氨基酸肽的复合物的数据进行比较。发现气相中含赖氨酸肽复合物的结合强度几乎与含精氨酸复合物的一样强。这两个体系的结合都比先前研究的含组氨酸肽更强。为了探究精氨酸和赖氨酸非共价复合物的结构（电荷溶剂化与盐桥），使用了两种技术，即CID和离子 - 分子反应。CID实验表明，气相复合物很可能是由金属卟啉中心金属离子通过精氨酸或赖氨酸的碱性侧链进行电荷溶剂化形成的。离子 - 分子反应研究的结果也与电荷溶剂化结构一致。
