Related Experiment Video
Updated: Jun 19, 2026
12:06
Molecular Diffusion in Plasma Membranes of Primary Lymphocytes Measured by Fluorescence Correlation Spectroscopy
Published on: February 1, 2017
Diffusion in Model Networks as Studied by NMR and Fluorescence Correlation Spectroscopy
Macromolecules
|October 9, 2009
Summary
We studied how small molecules and large dyes move in polymer solutions and networks. Cross-links restrict larger molecules, while smaller ones are less affected, influencing diffusion theories.
Area of Science:
- Polymer Science
- Materials Science
- Physical Chemistry
Background:
- Understanding diffusion in polymer systems is crucial for materials design.
- Polymer networks exhibit complex diffusion behaviors influenced by cross-linking and swelling.
- Existing theories for probe diffusion in concentrated polymers require validation.
Purpose of the Study:
- To investigate the diffusion of small solvent molecules and larger dye probes in poly(dimethyl siloxane) solutions and networks.
- To compare diffusion behaviors in linear polymer solutions versus cross-linked networks.
- To evaluate the applicability of different diffusion theories in concentrated polymer systems.
Main Methods:
- Pulsed-gradient nuclear magnetic resonance (NMR) for small molecule diffusion (octane).
- Fluorescence correlation spectroscopy (FCS) for larger dye probe diffusion.
- Studied diffusion in linear polymer solutions and end-linked model networks up to equilibrium swelling.
Main Results:
- Octane diffusion was independent of cross-link density.
- Larger dye probes showed diffusion restricted by the polymer network's cross-links.
- Fujita free-volume theory provided a feasible description for linear solutions, with improved fits using stretched exponential dependence.
- Cross-link effects were additive to the effective friction coefficient.
Conclusions:
- Cross-links significantly impede the diffusion of larger probes but not small solvent molecules.
- The Fujita theory and stretched exponential models offer insights into polymer diffusion.
- Swelling heterogeneities and diffusant shape play a substantial role in diffusion within polymer networks.
More Related Videos
14:12Dual-Color Fluorescence Cross-Correlation Spectroscopy to Study Protein-Protein Interaction and Protein Dynamics in Live Cells
Published on: December 11, 2021
05:56Spot Variation Fluorescence Correlation Spectroscopy for Analysis of Molecular Diffusion at the Plasma Membrane of Living Cells
Published on: November 12, 2020
Related Concept Videos
01:24Protein 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...
01:19Protein Dynamics in Living Cells
Different fluorescence-based techniques are used to study the protein dynamics in living cells. These techniques include FRAP, FRET, and PET.
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...
01:182D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
01:12Diffusion
Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
00:57Physiological Pharmacokinetic Models: Blood Flow-Limited Versus Diffusion-Limited Models
Physiological pharmacokinetic models, often called flow-limited or perfusion models, typically assume a swift drug distribution between tissue and venous blood, creating a rapid drug equilibrium. This premise is based on the idea that drug diffusion is extremely fast, and the cell membrane presents no barrier to drug permeation. In this scenario, where no drug binding occurs, the drug concentration in the tissue equals that of the venous blood leaving the tissue. This greatly simplifies the...
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...