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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Supramolecular Modification of Ion Chemistry: Modulation of Peptide Charge State and Dissociation Behavior through Complexation with Cucurbit[n]uril (n=5, 6) or alpha-Cyclodextrin
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Supramolecular Modification of Ion Chemistry: Modulation of Peptide Charge State and Dissociation Behavior through Complexation with Cucurbit[n]uril (n=5, 6) or alpha-Cyclodextrin

机译：离子化学的超分子修饰：通过与葫芦[n] uril（n = 5，6）或α-环糊精络合来调节肽的电荷状态和解离行为

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Electrospray Fourier transform ion cyclotron resonance mass spectrometry, ion mobility spectrometry, and computational methods were utilized to characterize the complexes between lysine or pentalysine with three prototypical host molecules: alpha-cyclodextrin (alpha-CD), cucurbit[5]uril (CB[5]), and cucurbit[6]uril (CB[6]). Ion mobility measurements show lysine forms externally bound, singly charged complexes with either alpha-CD or CB[5], but a doubly charged complex with the lysine side chain threaded through the host cavity of CB[6]. These structural differences result in distinct dissociation behaviors in collision-induced dissociation (CID) experiments: the alpha-CD complex dissociates via the simple loss of intact lysine, whereas the CB[5] complex dissociates to yield [CB[5] + H3O](+), and the CB[6] complex loses neutral NH3 and CO, the product ion remaining a doubly charged complex. These results are consistent with B3LYP/6-31G* binding energies (kJ mol(-1)) of D(Lys + H+-alpha-CD) = 281, D(Lys + H+-CB[5]) = 327, and D(Lys + 2H(2+)-CB[6]) = 600. B3LYP/6-31G* geometry optimizations show complexation with alpha-CD stabilizes the salt bridge form of protonated lysine, whereas complexation with CB[6] stabilizes doubly protonated lysine. Complexation of the larger polypeptide pentalysine with alpha-CD forms a nonspecific adduct: no modification of the pentalysine charge state distribution is observed, and dissociation occurs via the simple loss of alpha-CD. Complexation of pentalysine with the cucurbiturils is more specific: the observed charge state distribution shifts higher on complexation, and fragmentation patterns are significantly altered relative to uncomplexed pentalysine: C-terminal fragment ions appear that are consistent with charge stabilization by the cucurbiturils, and the cucurbiturils are retained on the fragment ions. Molecular mechanics calculations suggest CB[5] binds to two protonated sites on pentalysine without threading onto the peptide and that CB[6] binds two adjacent protonated sites via threading onto the peptide.
机译：利用电喷雾傅里叶变换离子回旋共振质谱，离子迁移谱和计算方法来表征赖氨酸或戊赖氨酸与三种原型宿主分子之间的配合物：α-环糊精（α-CD），葫芦[5] uril（CB [5 ]）和葫芦丝[6] uril（CB [6]）。离子迁移率测量显示，赖氨酸与α-CD或CB形成外部结合的单电荷复合物，但赖氨酸侧链穿过CB的主腔则形成双电荷复合物[6]。这些结构上的差异导致在碰撞诱导解离（CID）实验中产生不同的解离行为：α-CD复合物通过完整赖氨酸的简单损失而解离，而CB [5]复合物则解离生成[CB [5] + H3O] （+），而CB [6]络合物失去中性NH3和CO，产物离子仍然是双电荷的络合物。这些结果与D（Lys + H +-α-CD）= 281，D（Lys + H + -CB [5]）= 327的B3LYP / 6-31G *结合能（kJ mol（-1））一致。 D（Lys + 2H（2 +）-CB [6]）=600。B3LYP/ 6-31G *几何优化显示，与α-CD的络合稳定了质子化赖氨酸的盐桥形式，而与CB [6]的络合则使双重稳定质子化赖氨酸。较大的多肽戊赖氨酸与α-CD的络合形成非特异性加合物：未观察到戊赖氨酸电荷状态分布的改变，并且通过α-CD的简单丢失发生离解。五赖氨酸与葫芦嘧啶的络合作用更具体：观察到的电荷状态分布在络合时变化更高，并且碎裂模式相对于未络合的五赖氨酸显着改变：C末端碎片离子的出现与葫芦嘧啶和葫芦丁的电荷稳定相符被保留在碎片离子上分子力学计算表明，CB [5]结合到五赖氨酸上的两个质子化位点，而没有穿线到肽上，而CB [6]结合了两个相邻的质子化位点，通过穿线到肽上。

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