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Related Concept Videos

The Blood-brain Barrier00:49

The Blood-brain Barrier

Overview
Protein Diffusion in the Membrane01:24

Protein Diffusion in the Membrane

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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Physiological barriers are semi-permeable cellular structures restricting drug diffusion into intracellular compartments and tissues. There are six types of physiological barriers: blood endothelial, cell membrane, blood-brain, blood-cerebrospinal fluid (CSF), blood-placenta, and blood-testis barriers.
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Updated: May 16, 2026

Real-time Iontophoresis with Tetramethylammonium to Quantify Volume Fraction and Tortuosity of Brain Extracellular Space
10:45

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Published on: July 24, 2017

Brain Extracellular Space as a Diffusion Barrier.

Charles Nicholson1, Padideh Kamali-Zare, Lian Tao

  • 1Department of Physiology & Neuroscience, New York University School of Medicine, 550 First Avenue, New York, NY 10016, USA.

Computing and Visualization in Science
|November 23, 2012
PubMed
Summary
This summary is machine-generated.

The extracellular space (ECS) in the brain acts as a diffusion barrier, slowing molecule movement by approximately 2.6 times. Understanding ECS properties is crucial for predicting molecular transport and brain function.

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Area of Science:

  • Neuroscience
  • Biophysics
  • Computational Biology

Background:

  • The extracellular space (ECS) constitutes 20% of brain volume, with narrow channels (20-60 nm) between brain cells.
  • Molecular diffusion in the ECS is significantly impeded, with an effective diffusion coefficient reduced by a factor of ~2.6 compared to free diffusion.

Purpose of the Study:

  • To review the origins and properties of the diffusion barrier within the brain's ECS.
  • To discuss methods for measuring localized diffusion properties and the role of geometrical constraints.

Main Methods:

  • Overview of software for two point-source paradigms: real-time iontophoresis/pressure (small ions) and integrative optical imaging (macromolecules).
  • Application of MCell Monte Carlo simulations to assess geometrical constraints and extracellular matrix interactions.

Main Results:

  • Experimental and simulation data demonstrate the significant impediment to diffusion caused by ECS geometry and composition.
  • Selected results highlight localized diffusion measurements and the impact of microdomains.

Conclusions:

  • The diffusion barrier properties of the ECS can be predicted for molecules of practical importance.
  • Studying molecular probe diffusion reveals critical information about ECS barrier characteristics.