Single-molecule force spectroscopy of supramolecular heterodimeric capsules.
The specific interaction of a supramolecular binding motif was quantitatively evaluated by dynamic single-molecule force spectroscopy (SMFS) using an atomic force microscope (AFM). The supramolecular capsule forms by two different cavitands stitched together by four hydrogen bonds between carboxylic acid and pyridyl groups. The tetra(carboxyl)cavitand is monofunctionalized at the lower rim with a flexible poly(ethylene glycol) linker and attached to the AFM sensor tip. Single-molecule association experiments are accomplished using a diluted self-assembled monolayer (SAM) of the tetra(pyridyl)cavitand on a gold substrate. The measured single-molecule dissociation forces of the heterodimeric capsule represent the mechanical stability of the supramolecular system and allow a quantitative evaluation of the interaction according to the Bell-Evans model yielding dissociation rate constant k(off) = (0.14 +/- 0.14) s(-1), reaction length x(beta) = (0.56 +/- 0.076) nm and an estimated value of DeltaG(0) = -27 kJ mol(-1).
Schröder
Tobias
T
Organic Chemistry I, Chemistry Faculty, Bielefeld University, Universitätsstrasse 25, 33615 Bielefeld, Germany.
Geisler
Thomas
T
Walhorn
Volker
V
Schnatwinkel
Björn
B
Anselmetti
Dario
D
Mattay
Jochen
J
D002214:Capsules; D002264:Carboxylic Acids / Q000737:chemistry; D019281:Dimerization; D006860:Hydrogen Bonding; D007700:Kinetics; D018625:Microscopy, Atomic Force; D011092:Polyethylene Glycols / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013057:Spectrum Analysis; D014992:Xylenes / Q000737:chemistry*
D002214:Capsules; D002264:Carboxylic Acids; D011725:Pyridines; D012997:Solvents; D014992:Xylenes; D011092:Polyethylene Glycols; C023666:pyridine