Molecular binding behavior of pyridine-2,6-dicarboxamide-bridged bis(β-cyclodextrin) with oligopeptides : switchable molecular binding mode

• Main Authors: Liu, Yu, Chen, Guo Song, Chen, Yong, Ding, Fei, Liu, Tao, Zhao, Yanli
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2011
• Subjects: DRNTU::Science::Biological sciences::Biochemistry
• Online Access: https://hdl.handle.net/10356/92082; http://hdl.handle.net/10220/7035
• Institution: Nanyang Technological University

Bridged bis(β-cyclodextrin) 1 with a pyridine-2,6-dicarboxamide linker was synthesized, and its inclusion complexation behavior with some aliphatic oligopeptides was investigated in aqueous buffer solution of pH 2.0 and 7.2 at 25 °C by means of circular dichroism, fluorescence, and 2D NMR techniques. The results show that the resulting inclusion complexes of 1 with oligopeptides adopt a cooperative “cyclodextrin-guest-cyclodextrin” sandwich binding mode in a neutral media, but a “guest-linker-cyclodextrin” coinclusion binding mode in an acidic media. These switchable binding modes consequently rationalize the binding ability of bis(β -cyclodextrin) 1 at different pH values; that is, 1 shows the stronger association with oligopeptides in a neutral media. Because of the simultaneous contributions of hydrophobic, hydrogen bond, and electrostatic interactions, bis(β-cyclodextrin) 1 affords length-selectivity up to 4.7 for the Gly-Gly/Gly-Gly-Gly pair at pH 2.0 and sequence-selectivity up to 4.2 for the Gly-Leu/Leu-Gly pair at pH 7.2. These phenomena are discussed from the viewpoint of the size-fit concept and the multipoint recognitions between host and guest.