Related Experiment Video
Updated: Jun 6, 2026
08:28
Single-molecule Manipulation of G-quadruplexes by Magnetic Tweezers
Published on: September 19, 2017
Folding and unfolding movements in a [2]pseudorotaxane
Moorthy Suresh1, Amal Kumar Mandal, Manoj K Kesharwani
1Central Salt and Marine Chemicals Research Institute (CSIR), Bhavnagar, Gujarat, India.
The Journal of Organic Chemistry
|December 9, 2010
Summary
A novel crown ether derivative featuring naphthalene and coumarin units exhibits reversible conformational changes upon binding imidazolium ions. This molecular folding-unfolding behavior modulates Forster resonance energy transfer (FRET) efficiency, demonstrating a chemically responsive system.
Area of Science:
- Supramolecular Chemistry
- Organic Chemistry
- Photochemistry
Background:
- Crown ether derivatives are crucial in host-guest chemistry.
- Forster resonance energy transfer (FRET) is a key photophysical process.
- Designing responsive molecular systems requires understanding conformational dynamics.
Purpose of the Study:
- To synthesize and characterize a dibenzo[24]crown-8 derivative functionalized with naphthalene and coumarin fluorophores.
- To investigate the conformational changes and FRET efficiency modulation upon complexation with imidazolium ions.
- To demonstrate a chemically induced molecular folding-unfolding mechanism in a crown ether system.
Main Methods:
- Synthesis of a novel dibenzo[24]crown-8 derivative.
- Steady-state and time-resolved fluorescence spectroscopy to study FRET.
- Nuclear Magnetic Resonance (NMR) spectroscopy and computational studies for conformational analysis.
- Single-crystal X-ray diffraction for structural elucidation of inclusion complexes.
- Reversibility studies using base/polar solvent treatment.
Main Results:
- The synthesized crown ether (1) exhibits intramolecular FRET between naphthalene (donor) and coumarin (acceptor).
- Uncomplexed crown ether (1) adopts a folded conformation, while complexation with imidazolium ions ([C(4)mim]+ or [C(10)mim]+) induces an open conformation ([2]pseudorotaxane formation).
- Complexation leads to decreased FRET efficiency due to increased distance between fluorophores, which is reversible upon guest removal, restoring FRET and original emission spectra.
Conclusions:
- The crown ether derivative acts as a molecular machine, undergoing reversible folding-unfolding motions triggered by imidazolium ion binding.
- The conformational change directly impacts the FRET efficiency, providing a mechanism for optical signal transduction.
- This study demonstrates the potential of functionalized crown ethers for developing chemically responsive and switchable molecular systems.
Related Concept Videos
02:02Chair Conformation of Cyclohexane
The chair conformation is the most stable form of cyclohexane due to the absence of angle and torsional strain. The absence of angle strain is a result of cyclohexane’s bond angle being very close to the ideal tetrahedral bond angle of 109.5° in its chair conformer. Similarly, the torsional strain is also absent owing to the perfectly staggered arrangement of bonds.
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...
01:22Protein Folding
Overview
01:25Protein Folding
Proteins are chains of amino acids linked together by peptide bonds. Upon synthesis, a protein folds into a three-dimensional conformation, critical to its biological function. Interactions between its constituent amino acids guide protein folding, and hence the protein structure is primarily dependent on its amino acid sequence.
Protein Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...
Protein Structure Is Critical to Its Biological Function
Proteins perform a wide range of biological functions such as catalyzing chemical reactions, providing...
01:22Protein Folding
Overview
00:52¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
At room temperature, the chair conformer of cyclohexane undergoes rapid ring flipping between two equivalent chair conformers at a rate of approximately 105 times per second. These two chair conformers are in equilibrium. The rapid ring flipping results in the interconversion of the axial proton to an equatorial proton and an equatorial to the axial proton. Such interconversions are too rapid and cannot be detected on the NMR timescale. Hence, the NMR spectrometer cannot distinguish between the...
02:11Conformations of Cyclohexane
Cyclohexane does not exist in a planar form due to the high angle and torsional strain it would experience in the planar structure. Instead, it adopts non-planar chair and boat conformations.
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...
The chair form is the most stable and derives its name from its resemblance to the “easy chair.” In the chair conformation, two carbon atoms are arranged out-of-plane — one above and one below, minimizing the torsional strain. In the chair form, the bond angle is very close to the ideal tetrahedral value,...