A kind of protein complexes of cytochrome C with L-Arg was observed. Using L-Arg a strategy for probing the structural information of cytochrome C and protein complexes was established. At low pH solution multiply L-A...A kind of protein complexes of cytochrome C with L-Arg was observed. Using L-Arg a strategy for probing the structural information of cytochrome C and protein complexes was established. At low pH solution multiply L-Arg adducts were produced and the number of binding ligand was depended on the charge state. While in neutral solution only these complexes binding with single L-Arg ligand were produced.展开更多
为了探索侧链R基团对碱金属离子与多肽复合物气相裂解反应的影响,采用电喷雾电离质谱法研究了碱金属离子Li^+,Na^+和K^+分别与甘氨酸三肽(GGG)、甘氨酰-苯丙氨酰-甘氨酸三肽(GFG)和甘氨酰-甘氨酰-苯丙氨酸三肽(GGF)形成的复合物的气相...为了探索侧链R基团对碱金属离子与多肽复合物气相裂解反应的影响,采用电喷雾电离质谱法研究了碱金属离子Li^+,Na^+和K^+分别与甘氨酸三肽(GGG)、甘氨酰-苯丙氨酰-甘氨酸三肽(GFG)和甘氨酰-甘氨酰-苯丙氨酸三肽(GGF)形成的复合物的气相裂解反应.质谱定性实验结果表明,Li^+,Na^+和K^+与GGG,GFG或GGF在气相中可以形成稳定的复合物,配合比为1∶1或2∶1.竞争反应质谱图显示,GGG,GFG或GGF与碱金属离子形成的复合物的质谱峰丰度按Li^+,Na^+,K^+顺序依次下降,表明随着碱金属离子半径的增加,它们与三肽的结合强度依次减弱.碰撞诱导解离显示,母体离子[GGG+Na]^+,[GGF+Na]^+和[GFG+Na]^+的质心碰撞能量E(CM)50数值分别为1.94,1.76和1.63 e V.通过质谱滴定法测得[GGG+Na]^+,[GFG^+Na]^+和[GGF+Na]^+的结合常数lg Ka1分别为5.30,5.25和5.17.质谱法定量结果进一步确认复合物的稳定性顺序为[GGG+Na]^+>[GGF+Na]^+>[GFG+Na]^+,表明由于空间位阻的影响,侧链R基团含有苄基的GFG或GGF与Na^+的键合强度要小于侧链R全部为H的GGG.串级质谱分析结果显示,碱金属化的GGG断裂位点较多,可解离出丰富的金属化a2,b和y型碎片离子,而碱金属化的GGF和GFG解离出的金属化y型离子较多,b型离子其次,金属化a型离子几乎没有.此外,双碱金属化的GGF可解离出较多金属化y型离子.复合物[GGF+Na]^+的裂解曲线显示,当碰撞能量为25 e V时,[y2+Na-H]^+和[b2+Na+OH]^+为主要碎片离子,当碰撞能量>40 e V时,只有[b2+Na+OH]^+碎片离子占有优势数量.根据质子化三肽裂解机理可以推测,钠化GFG裂解后生成含噁唑酮的[b2+Na]^+离子,该离子经过一系列过渡态生成[a2+Na]^+(2-苄基-4-咪唑酮),而不是常见的亚胺离子.展开更多
文摘A kind of protein complexes of cytochrome C with L-Arg was observed. Using L-Arg a strategy for probing the structural information of cytochrome C and protein complexes was established. At low pH solution multiply L-Arg adducts were produced and the number of binding ligand was depended on the charge state. While in neutral solution only these complexes binding with single L-Arg ligand were produced.
文摘为了探索侧链R基团对碱金属离子与多肽复合物气相裂解反应的影响,采用电喷雾电离质谱法研究了碱金属离子Li^+,Na^+和K^+分别与甘氨酸三肽(GGG)、甘氨酰-苯丙氨酰-甘氨酸三肽(GFG)和甘氨酰-甘氨酰-苯丙氨酸三肽(GGF)形成的复合物的气相裂解反应.质谱定性实验结果表明,Li^+,Na^+和K^+与GGG,GFG或GGF在气相中可以形成稳定的复合物,配合比为1∶1或2∶1.竞争反应质谱图显示,GGG,GFG或GGF与碱金属离子形成的复合物的质谱峰丰度按Li^+,Na^+,K^+顺序依次下降,表明随着碱金属离子半径的增加,它们与三肽的结合强度依次减弱.碰撞诱导解离显示,母体离子[GGG+Na]^+,[GGF+Na]^+和[GFG+Na]^+的质心碰撞能量E(CM)50数值分别为1.94,1.76和1.63 e V.通过质谱滴定法测得[GGG+Na]^+,[GFG^+Na]^+和[GGF+Na]^+的结合常数lg Ka1分别为5.30,5.25和5.17.质谱法定量结果进一步确认复合物的稳定性顺序为[GGG+Na]^+>[GGF+Na]^+>[GFG+Na]^+,表明由于空间位阻的影响,侧链R基团含有苄基的GFG或GGF与Na^+的键合强度要小于侧链R全部为H的GGG.串级质谱分析结果显示,碱金属化的GGG断裂位点较多,可解离出丰富的金属化a2,b和y型碎片离子,而碱金属化的GGF和GFG解离出的金属化y型离子较多,b型离子其次,金属化a型离子几乎没有.此外,双碱金属化的GGF可解离出较多金属化y型离子.复合物[GGF+Na]^+的裂解曲线显示,当碰撞能量为25 e V时,[y2+Na-H]^+和[b2+Na+OH]^+为主要碎片离子,当碰撞能量>40 e V时,只有[b2+Na+OH]^+碎片离子占有优势数量.根据质子化三肽裂解机理可以推测,钠化GFG裂解后生成含噁唑酮的[b2+Na]^+离子,该离子经过一系列过渡态生成[a2+Na]^+(2-苄基-4-咪唑酮),而不是常见的亚胺离子.
