Chaperone-Assisted Host-Guest Interactions Revealed by Single-Molecule Force Spectroscopy

J Am Chem Soc. 2019 Nov 20;141(46):18385-18389. doi: 10.1021/jacs.9b09019. Epub 2019 Nov 11.

Abstract

The recent discovery of ultra-high binding affinities in cucurbit[7]uril (CB7)-based host-guest pairs in an aqueous environment has rendered CB7 a rather attractive material in analytical and biomedical applications. Due to the lack of a molecular platform that can follow the same host-guest complex during repetitive mechanical measurements, however, mechanical stabilities of the CB7 system have not been revealed, hindering its potential to rival widely used conjugation pairs, such as streptavidin-biotin. Here, we assembled a DNA template in which a flexible DNA linker was exploited to keep the host (CB7) and guest (adamantane) in proximity. This platform not only increased the efficiency of the single-molecule characterization in optical tweezers but also clearly revealed mechanical features of the same host-guest complex. We found that positively charged adamantane guest demonstrated higher mechanical stability (49 pN) than neutral adamantane (44 pN), a trend consistent with the chemical affinity between guest molecules and the CB7 host. Surprisingly, we found that a hexyl group adjacent to the adamantane served as a chaperone to assist the formation of the adamantane-CB7 pairs. The discovery of an unprecedented chaperone-assisted interaction mechanism provides new approaches to efficiently assemble host-guest-based supramolecules with increased mechanical stabilities, which can be exploited in various biomedical, biosensing, and materials fields.

MeSH terms

  • Adamantane / chemistry*
  • Bridged-Ring Compounds / chemistry*
  • DNA / chemistry*
  • Imidazoles / chemistry*
  • Optical Tweezers
  • Single Molecule Imaging
  • Stress, Mechanical

Substances

  • Bridged-Ring Compounds
  • Imidazoles
  • cucurbit(7)uril
  • DNA
  • Adamantane