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Related Concept Videos

Cryo-electron Microscopy01:28

Cryo-electron Microscopy

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Conventional electron microscopy (EM) involves dehydration, fixation, and staining of biological samples, which distorts the native state of biological molecules and results in several artifacts. Also, the high-energy electron beam damages the sample and makes it difficult to obtain high-resolution images. These issues can be addressed using cryo-EM, which uses frozen samples and gentler electron beams. The technique was developed by Jacques Dubochet, Joachim Frank, and Richard Henderson, for...
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Cell membranes are composed of phospholipids, proteins, and carbohydrates loosely attached to one another through chemical interactions. Molecules are generally able to move about in the plane of the membrane, giving the membrane its flexible nature called fluidity. Two other features of the membrane contribute to membrane fluidity: the chemical structure of the phospholipids and the presence of cholesterol in the membrane.
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Membrane Fluidity01:26

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Membrane fluidity is explained by the fluid mosaic model of the cell membrane, which describes the plasma membrane structure as a mosaic of components—including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character.
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Proteins show rotational as well as lateral diffusion across the membrane. The lateral diffusion of proteins was confirmed through the cell fusion experiment where mouse and human cells were fused, resulting in hybrid cells. When the human and mouse cells fused, the specific membrane proteins on human and mouse cells were marked with the red and green-fluorescent markers, respectively. Initially, the red and green fluorescence was located on the respective hemisphere of the cell. As time...
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The spontaneity of a process depends upon the temperature of the system. Phase transitions, for example, will proceed spontaneously in one direction or the other depending upon the temperature of the substance in question. Likewise, some chemical reactions can also exhibit temperature-dependent spontaneities. To illustrate this concept, the equation relating free energy change to the enthalpy and entropy changes for the process is considered:
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Diversity of Archaea IV

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Hyperthermophilic archaea are a group of extremophiles thriving at temperatures above 80°C, often in hydrothermal vents and volcanic soils where conditions surpass the boiling point of water. At such temperatures, proteins, membranes, and DNA in most organisms degrade, but hyperthermophiles have evolved remarkable adaptations to maintain stability and function.Unique Cellular FeaturesHyperthermophilic membranes are composed of a monolayer of biphytanyl tetraether lipids, which resist...
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Related Experiment Video

Updated: Dec 30, 2025

Flash-and-Freeze: A Novel Technique to Capture Membrane Dynamics with Electron Microscopy
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Cryo-temperature effects on membrane protein structure and dynamics.

Rukmankesh Mehra1, Budheswar Dehury1, Kasper P Kepp1

  • 1DTU Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark. kpj@kemi.dtu.dk.

Physical Chemistry Chemical Physics : PCCP
|January 24, 2020
PubMed
Summary
This summary is machine-generated.

Cryo-electron microscopy (Cryo-EM) structures may differ from physiological states. Molecular dynamics simulations reveal cooling effects on gamma-secretase, suggesting methods to refine Cryo-EM data for Alzheimer's disease research.

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The CryoAPEX Method for Electron Microscopy Analysis of Membrane Protein Localization Within Ultrastructurally-Preserved Cells
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Harvesting and Cryo-cooling Crystals of Membrane Proteins Grown in Lipidic Mesophases for Structure Determination by Macromolecular Crystallography
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Area of Science:

  • Structural biology
  • Biophysics
  • Computational biology

Background:

  • Cryo-electron microscopy (Cryo-EM) provides high-resolution protein structures.
  • Protein freezing during Cryo-EM can alter structures and dynamics compared to physiological "hot" states.
  • Gamma-secretase, a membrane protease producing amyloid-beta (Aβ), is crucial in Alzheimer's disease (AD).

Purpose of the Study:

  • To investigate the structural and dynamic changes of substrate-bound gamma-secretase (6IYC) upon cooling.
  • To compare simulated "hot", "cold", and "cooled" states with experimental Cryo-EM structures.
  • To propose methods for correcting Cryo-EM coordinates using molecular dynamics (MD) simulations.

Main Methods:

  • Molecular dynamics (MD) simulations of substrate-bound gamma-secretase (6IYC).
  • Simulations were performed at different temperatures (hot, cold, quickly cooled) and environments (membrane, water).
  • Analysis of structural parameters like radius of gyration (Rg) and secondary structure elements (α-helix, β-sheet).

Main Results:

  • Experimental Cryo-EM structure aligns with the simulated "cooled" state, intermediate between "hot" and "cold" states.
  • "Cryo-contraction" observed in the membrane environment upon cooling (303 K to 85 K).
  • Hot state exhibits an unwound C83-substrate and temperature-dependent weakening of β-sheet structure, potentially influencing Aβ42/Aβ40 ratio.

Conclusions:

  • MD simulations of different temperature states can help correct Cryo-EM coordinates.
  • Observed "cryo-contraction" and altered dynamics highlight the impact of freezing on protein structure.
  • Fast dynamic modes, "frozen-out" in Cryo-EM, may require supplementary hot simulations or experiments for full characterization.