title: Allosteric Regulation of Unidirectional Spring-like Motion of Double-Stranded Helicates.
abstract: We report the unprecedented allosteric regulation of the extension and contraction motions of double-stranded spiroborate helicates composed of 4,4'-linked 2,2'-bipyridine (bpy) and its N,N'-dioxide units in the middle of ortho-linked tetraphenol strands. NMR and circular dichroism measurements and an X-ray crystallographic analysis along with theoretical calculations revealed that enantiomeric helicates contract and extend upon the binding and release of protons and/or metal ions at the covalently linked two binding bpy or N,N'-dioxide moieties without racemization, respectively, regulated by a cooperative anti-syn conformational change of the two bpy or N,N'-dioxide moieties. These anti-syn conformational changes that occurred at the linkages are amplified into a large-scale molecular motion of the helicates leading to reversible spring-like motions coupled with twisting in one direction in a highly homotropic allosteric fashion.
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Taiki
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Iida
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ousaka
authors.affiliation: Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Yashima