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Related Concept Videos

Chair Conformation of Cyclohexane02:02

Chair Conformation of Cyclohexane

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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...
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The Contractile Ring02:15

The Contractile Ring

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Contractile rings are composed of microfilaments and are responsible for separating the daughter cells during cytokinesis. Contractile ring assembly proceeds along with other cell cycle events; however, very few mechanistic details are known about the timing and coordination of the contractile rings with the cell cycle.
A small GTPase, RhoA, controls the function and assembly of the contractile ring. RhoA belongs to the Ras superfamily of proteins. The activation of formins by RhoA promotes...
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Conformations of Cycloalkanes02:29

Conformations of Cycloalkanes

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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...
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Stereoisomerism of Cyclic Compounds02:33

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In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
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Conformations of Cyclohexane02:11

Conformations of Cyclohexane

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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...
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Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)01:16

Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)

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Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...
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Directed Cellular Self-Assembly to Fabricate Cell-Derived Tissue Rings for Biomechanical Analysis and Tissue Engineering
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Packing structure of semiflexible rings.

Leopoldo R Gómez1, Nicolás A García2, Thorsten Pöschel3

  • 1Department of Physics, Universidad Nacional del Sur-IFISUR-CONICET, 8000 Bahía Blanca, Argentina; lgomez@uns.edu.ar.

Proceedings of the National Academy of Sciences of the United States of America
|February 7, 2020
PubMed
Summary

Dense polymer ring packing is crucial for understanding biological packaging. X-ray tomography reveals that longer rubber bands form complex, entangled structures within confined spaces, unlike shorter bands.

Keywords:
X-ray tomographyentanglementsfilamentous mattergeometrytopology

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Area of Science:

  • Polymer Physics
  • Soft Matter Physics
  • Biophysics

Background:

  • Understanding the packing of semiflexible rings is essential for polymer dynamics and biological packaging, such as viral circular DNA and genome folding.
  • Disordered packings of polymer rings present complex geometrical and topological challenges.
  • Semiflexible rings are model systems for various biological and synthetic materials.

Purpose of the Study:

  • To investigate the geometrical and topological features of dense, disordered assemblies of semiflexible rings (rubber bands) in a cylindrical container.
  • To determine the influence of ring length and confinement on the packing structure.
  • To explore the formation of entangled networks within these assemblies.

Main Methods:

  • Utilized X-ray tomography to visualize and analyze the 3D structure of packed rubber bands.
  • Studied assemblies of varying rubber band lengths under cylindrical confinement.
  • Quantified geometrical and topological properties of the band packings.

Main Results:

  • Short rubber bands form liquid-like disordered structures with minimal container influence and short-range orientational order.
  • Longer rubber bands exhibit folded configurations due to confinement, leading to interpenetration and entanglement.
  • A percolating threading network was observed in most systems.
  • For very long bands (diameter > 2x container diameter), a complex, fully entangled structure emerged where all bands interpenetrate.

Conclusions:

  • The packing structure of semiflexible rings is highly dependent on ring length and degree of confinement.
  • Confinement induces significant changes in ring conformation, promoting entanglement and network formation.
  • The study provides insights into the fundamental principles governing the packaging of ring-like polymers, relevant to both synthetic materials and biological systems.