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Related Concept Videos

Conformations of Ethane and Propane02:18

Conformations of Ethane and Propane

In an organic molecule, free rotation about the carbon-carbon single bond results in energetically different conformers of the molecule. Due to this rotation, called the internal rotation, ethane has two major conformations — staggered and eclipsed.
Staggered conformation is a low energy and more stable conformation with the C-H bonds on the front carbon placed at 60°dihedral angles relative to the C-H bonds on the back carbon, leading to a reduced torsional strain. In staggered ethane, the...
Conformations of Butane02:20

Conformations of Butane

Unlike ethane and propane that have only two major conformations, butane has more than two conformers. The staggered form of butane in which the bulky methyl groups on the two carbons are placed on opposite sides, that is, at a dihedral angle of 180°, is the lowest energy, most stable form — called the anti conformer. This conformation is stabilized due to the absence of steric repulsion between the largely spaced out methyl groups. The other two staggered conformations are degenerate and have...
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...
Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules02:34

Kinetic Molecular Theory and Gas Laws Explain Properties of Gas Molecules

The test of the kinetic molecular theory (KMT) and its postulates is its ability to explain and describe the behavior of a gas. The various gas laws (Boyle’s, Charles’s, Gay-Lussac’s, Avogadro’s, and Dalton’s laws) can be derived from the assumptions of the KMT, which have led chemists to believe that the assumptions of the theory accurately represent the properties of gas molecules.
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.
Conformations of Cycloalkanes02:29

Conformations of Cycloalkanes

Adolf von Baeyer attempted to explain the instabilities of small and large cycloalkane rings using the concept of angle strain — the strain caused by the deviation of bond angles from the ideal 109.5° tetrahedral value for sp3  hybridized carbons. However, while cyclopropane and cyclobutane are strained, as expected from their highly compressed bond angles, cyclopentane is more strained than predicted, and cyclohexane is virtually strain-free. Hence, Baeyer’s theory that was based on the...

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Spatial Separation of Molecular Conformers and Clusters
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Spatial Separation of Molecular Conformers and Clusters

Published on: January 9, 2014

Why do GroEL ions exhibit two gas phase conformers?

Juan Fernandez de la Mora1

  • 1Mechanical Engineering Department, Yale University, New Haven, CT 06520-8286, USA. juan.delamora@yale.edu

Journal of the American Society for Mass Spectrometry
|October 12, 2012
PubMed
Summary

Electrosprayed GroEL protein ions exist in two gas-phase forms due to charge distribution on their cylindrical bases. This explains supercharging beyond the Rayleigh limit for non-spherical proteins.

Area of Science:

  • * Physical Chemistry
  • * Biophysics
  • * Mass Spectrometry

Background:

  • * The tetradecameric protein complex GroEL is known to exist in two distinct gas-phase conformers when electrosprayed.
  • * Understanding these conformers is crucial for interpreting mass spectrometry data of large biomolecules.

Purpose of the Study:

  • * To investigate the reasons behind the existence of two gas-phase conformers for electrosprayed GroEL ions.
  • * To explore the phenomenon of supercharging in electrosprayed proteins beyond the Rayleigh limit.

Main Methods:

  • * Analysis of electrosprayed GroEL ions using techniques sensitive to charge and conformation.
  • * Extrapolation of cross-section data to zero charge.
  • * Comparison of supercharging behavior between different conformers.

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Main Results:

  • * Both GroEL conformers exhibit similar cross-sections at zero charge but supercharge beyond the Rayleigh limit.
  • * One conformer supercharges significantly more than the other, suggesting differential charge accumulation.
  • * The observed supercharging is hypothesized to be linked to GroEL's cylindrical shape and charge accumulation on its bases.

Conclusions:

  • * The two conformers likely arise from asymmetric versus symmetric charge distribution on GroEL's bases.
  • * Non-spherical proteins can generally exceed the Rayleigh limit for charge.
  • * Electrospraying significantly alters protein conformation in the gas phase due to capillary and Coulombic forces.