Sterically Controlled Recognition of Macromolecular Sequence Information by Molecular Tweezers

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• 作者：Howard M. Colquhoun ; Zhixue Zhu ; Christine J. Cardin ; Yu Gan ; Michael G. B. Drew
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：December 26, 2007
• 年：2007
• 卷：129
• 期：51
• 页码：16163 - 16174
• 全文大小：469K
• 年卷期：v.129,no.51(December 26, 2007)
• ISSN：1520-5126

文摘

Sequence-specific binding is demonstrated between pyrene-based tweezer molecules andsoluble, high molar mass copolyimides. The binding involves complementary - stacking interactions,polymer chain-folding, and hydrogen bonding and is extremely sensitive to the steric environment aroundthe pyromellitimide binding-site. A detailed picture of the intermolecular interactions involved has beenobtained through single-crystal X-ray studies of tweezer complexes with model diimides. Ring-currentmagnetic shielding of polyimide protons by the pyrene "arms" of the tweezer molecule induces largecomplexation shifts of the corresponding ¹H NMR resonances, enabling specific triplet sequences to beidentified by their complexation shifts. Extended comonomer sequences (triplets of triplets in which themonomer residues differ only by the presence or absence of a methyl group) can be "read" by a mechanismwhich involves multiple binding of tweezer molecules to adjacent diimide residues within the copolymerchain. The adjacent-binding model for sequence recognition has been validated by two conceptually differentsets of tweezer binding experiments. One approach compares sequence-recognition events for copolyimideshaving either restricted or unrestricted triple-triplet sequences, and the other makes use of copolymerscontaining both strongly binding and completely nonbinding diimide residues. In all cases the nature andrelative proportions of triple-triplet sequences predicted by the adjacent-binding model are fully consistentwith the observed ¹H NMR data.