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Conformational Selection as the Mechanism of Guest Binding in a Flexible Supramolecular Host

  • Author(s): Hong, CM
  • Kaphan, DM
  • Bergman, RG
  • Raymond, KN
  • Toste, FD
  • et al.
Abstract

© 2017 American Chemical Society. This study offers a detailed mechanistic investigation of host-guest encapsulation behavior in a new enzyme-mimetic metal-ligand host and provides the first observation of a conformational selection mechanism (as opposed to induced fit) in a supramolecular system. The Ga4L4host described features a C3-symmetric ligand motif with meta-substituted phenyl spacers, which enables the host to initially self-assemble into an S4-symmetric structure and then subsequently isomerize to a T-symmetric tetrahedron for better accommodation of a sufficiently large guest. Selective inversion recovery1H NMR studies provide structural insights into the self-exchange behaviors of the host and the guest individually in this dynamic system. Kinetic analysis of the encapsulation-isomerization event revealed that increasing the concentration of guest inhibits the rate of host-guest relaxation, a key distinguishing feature of conformational selection. A comprehensive study of this simple enzyme mimic provides insight into analogous behavior in biophysics and enzymology and aims to inform the design of efficient self-assembled microenvironment catalysts.

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