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Related Concept Videos

Cooperative Allosteric Transitions01:58

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Cooperative Allosteric Transitions01:58

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Cooperative Allosteric Transitions01:58

Cooperative Allosteric Transitions

Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
Complexation Equilibria: The Chelate Effect01:19

Complexation Equilibria: The Chelate Effect

In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR01:15

¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR

The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution00:52

¹H 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...

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Time-Resolved Fluorescence Anisotropy from Single Molecules for Characterizing Local Flexibility in Biomolecules
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Relationship between conformational flexibility and chelate cooperativity.

M Cristina Misuraca1, Tudor Grecu, Zoraida Freixa

  • 1Department of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom.

The Journal of Organic Chemistry
|March 23, 2011
PubMed
Summary
This summary is machine-generated.

This study explores hydrogen-bonding interactions in biscarbamate-bisphenol complexes. Findings reveal a predictable relationship between chain flexibility and effective molarity, crucial for supramolecular chemistry.

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Area of Science:

  • Supramolecular Chemistry
  • Organic Chemistry
  • Chemical Physics

Background:

  • Hydrogen-bonding interactions are fundamental in molecular recognition and self-assembly.
  • Understanding the influence of conformational flexibility on noncovalent interactions is key for designing sophisticated molecular systems.

Purpose of the Study:

  • To synthesize and characterize biscarbamate-bisphenol complexes.
  • To investigate the relationship between the number of rotors in connecting chains and effective molarity (EM).
  • To analyze the impact of conformational flexibility on chelate cooperativity in noncovalent systems.

Main Methods:

  • Synthesis of biscarbamate (AA) and bisphenol (DD) families.
  • Characterization of H-bonding interactions using (1)H NMR titrations in carbon tetrachloride.
  • Chemical double mutant cycle analysis to probe secondary interactions.
  • Measurement of effective molarities (EMs) for 12 different AA•DD systems.

Main Results:

  • No significant secondary electrostatic interactions or allosteric cooperativity were observed.
  • Effective molarities (EMs) varied minimally (0.1-0.9 M) across systems with varying numbers of rotors.
  • A quantitative relationship was established: EM ≈ 10r(-3/2), where 'r' is the number of rotors.
  • Noncovalent EMs are limited compared to covalent processes, but flexibility's impact is less detrimental than anticipated.

Conclusions:

  • The studied systems provide a robust platform for investigating structure-chelate cooperativity relationships.
  • Conformational flexibility, quantified by rotors, predictably modulates effective molarity in noncovalent interactions.
  • Findings offer insights into designing supramolecular assemblies and catalysts with controlled binding affinities.