引用本文:
【打印本页】   【HTML】   【下载PDF全文】   View/Add Comment  【EndNote】   【RefMan】   【BibTex】
←前一篇|后一篇→ 过刊浏览    高级检索
本文已被:浏览 1834次   下载 1552 本文二维码信息
码上扫一扫!
分享到: 微信 更多
Investigation on Non-covalent Complexes of Cyclodextrins with Li+ in Gas Phase by Mass Spectrometry
Xiao-dan He,Wang-hui Wei,Yan-qiu Chu*,Zhi-pan Liu,Chuan-fan Ding
Author NameAffiliationE-mail
Xiao-dan He Laser Chemistry Institute, Department of Chemistry, Fudan University, Shanghai 200433, China  
Wang-hui Wei Laser Chemistry Institute, Department of Chemistry, Fudan University, Shanghai 200433, China  
Yan-qiu Chu* Laser Chemistry Institute, Department of Chemistry, Fudan University, Shanghai 200433, China chuyq@fudan.edu.cn 
Zhi-pan Liu Physical Chemistry Institute, Department of Chemistry, Fudan University, Shanghai 200433, China  
Chuan-fan Ding Physical Chemistry Institute, Department of Chemistry, Fudan University, Shanghai 200433, China  
Abstract:
To investigate the non-covalent interaction between cyclodextrins (CD) and lithium ion, a stoichiometry of α-CD, β-CD, heptakis(2,6-di-O-methyl)-β-CD (DM-β-CD), or heptakis(2,3,6-tri-O-methyl)-β-CD (TM-β-CD) was mixed with lithium salt, respectively, and then incubated at room temperature for 10 min to reach the equilibrium. In posi-tive mode, the electrospray ionization mass spectrometry (ESI-MS) results demonstrated that lithium ion can conjugate to α-, β-, DM-β- or TM-β-CD and form 1:1 stoichiometric non-covalent complexes. The binding of the complexes was further confirmed by collision-induced dissociation. The dissociation constants Kd1 of four complexes (Li+α-CD, Li+β-CD, Li+DM-β-CD, and Li+TM-β-CD) were determined by mass spectrometric titration. The results showed Kd1 were 18.7, 26.7, 33.6, 30.5 μmol/L for the complexes of Li+ with α-CD, β-CD, DM-β-CD, and TM-β-CD, respectively. Kd1 for the Li+ complexes of β-CD is smaller than that of DM-β-CD due to its steric effect of the partial substituted -CH3. The Kd1 for the Li+ complexes of DM-β-CD is nearly in agreement with that of TM-β-CD, indicating Li+ is more likely to locate in the small rim of DM-β-CD's hydrophobic cavity. The DFT results showed through electrostatic interaction, one Li+ can strongly conjugate to four neighboring oxygen atoms. For the (α-CD+Li)+ complex, one Li+ may also situate the small rim of α-CD's hydrophobic cavity to form a non-specific host-guest complex.
Key words:  Non-covalent complex, Lithium ion, Cyclodextrin, Dissociation constant, Mass spectrometry, Density functional theory calculation
FundProject:
电喷雾质谱研究气相中环糊精与锂离子的非共价复合物
何小丹,魏王慧,储艳秋*,刘智攀,丁传凡
摘要:
为了探索环糊精和锂离子的非共价相互作用,一定计量比的α-环糊精α-CD)、β-环糊精(β-CD)、七-(2,6-二-氧-甲基)-β-环糊精(DM-β-CD)和七-(2,3,6-三-氧-甲基)-β-环糊精(TM-β-CD)分别与氯化锂混合,在室温下反应10 min使达到平衡.溶剂组成为含70%乙腈的水溶液,甲酸含量为0.1%.正离子模式下,电喷雾质谱的结果表明环糊精可以和锂离子结合,并生成1:1化学计量比的非共价复合物.碰撞诱导解离观察到一系列带有锂的环糊精的碎片,表明碰撞后复合物失去了葡萄糖单元,进一步确认了该复合物的生成.质谱滴定法测定了四种复合物Li+α-CD、Li+β-CD、Li+DM-β-CD、Li+TM-β-CD的解离常数Kd1分别为1.87×10-5、2.67×10-5、3.36×10-5、3.05×10-5 mol/L.Li+和β-CD复合物的解离常数小于Li+和DM-β-CD复合物,其原因为部分甲基化的DM-β-CD具有较大的空间位阻.Li+和TM-β-CD复合物Kd1接近于Li+和DM-β-CD复合物,表明β-CD疏水腔的大口完全甲基化的TM-β-CD,与β-CD疏水腔的大口部分甲基化的DM-β-CD与锂离子结合能力相接近,该结果意味着锂离子与DM-β-CD疏水腔的结合位点很可能位于DM-β-CD疏水腔的小口.密度泛函理论计算结果表明,一个Li+可以和α-CD的四个相邻的氧原子结合,四个相邻的氧原子分别来自于伯羟基和糖苷键,它确认了Li+位于α-CD疏水腔的小口.对[α-CD+Li]+复合物而言,一个Li+可以通过静电作用,在小口与α-CD疏水腔作用,并形成非特异性结合的主客体复合物.
关键词:  非共价复合物,锂离子,环糊精,解离常数,质谱法,密度泛函理论计算
DOI:10.1063/1674-0068/26/03/287-294
分类号: