桥联双β-环糊精对N-[4-(1-芘基)]丁酰-D/L-苯丙氨酸的手性识别及机理研究

利用紫外-可见吸收和荧光发射光谱, 结合非线性最小二乘法拟合曲线以及分子力学(MM2)模拟系统地研究了手性分子N-[4-(1-芘基)]丁酰-D/L-苯丙氨酸(PDP和PLP, 总称PPs)与β-环糊精(β-CD)、 2-位硒桥联双β-CD(2-SeCD)和2-位碲桥联双β-CD(2-TeCD)的包结能力大小及这3个环糊精对PPs手性识别能力的差异和识别机理. 研究结果表明, PPs不能与单疏水空腔的β-CD形成很好的包结复合物, 与具有较长桥联链的2-TeCD结合能力最强. 2-TeCD与PDP和PLP的结合常数分别为2.33×104和6.07×103 L/mol, 对PPs的手性识别比达到KD/KL=3.84, 高于2-SeCD(KD/KL=2.61). 用MM2模拟得出了PPs与这两个双环糊精形成复合物的三维结构: PPs的绝大部分位于双环糊精两个空腔之间, 但是在这两个复合物中, 苯环与芘环所成的二面角不同. 此外, PPs与这两个双环糊精作用时均存在明显的氢键相互作用, 且2-TeCD强于2-SeCD.

Chiral Discrimination of N-[4(1-pyrene)butyroyl]-D/L-phenylalanine in Binding with Tellurium/Selenium Bridged-bis-β-cyclodextrins

The binding ability and chiral discrimination of β-cyclodextrin(β-CD), 2,2′-diseleno-bridged β-cyclodextrins(2-SeCD)and 2,2′-ditelluro-bridged β-cyclodextrins(2-TeCD)with PPs were investigated in aqueous solution by using UV-Vis and fluorescence spectroscopy as well as MM2 calculation. The stability constants of complexes were obtained by using least-square curve fitting. From the results of UV-Vis and fluorescence spectroscopy, it was shown that β-CD could not form inclusion complexation with PPs while 2-SeCD and 2-TeCD could. The binding ability between 2-TeCD and PDP was higher(Ks=2.33×104 L/mol) than that of 2-SeCD/PDP(Ks=3.03×103 L/mol). Meanwhile, the high chiral discrimination of PPs was also performed in binding with 2-TeCD(KD/KL=3.84)and 2-SeCD(KD/KL=2.61). Furthermore, the MM2 calculation illustrates that PPs were located between the two cavities of 2-SeCD or 2-TeCD, however, the dihedral angle between phenyl ring and pyrene ring was different from each other when they were included in two bis-cyclodextrins. Meanwhile, MM2 also demonstrates that the intermolecular hydrogen bonding interaction in 2-TeCD/PPs complex was relative stronger than that in 2-SeCD/PPs.