Related Experiment Video
Updated: Aug 7, 2026
10:43
Single-Molecule Diffusion and Assembly on Polymer-Crowded Lipid Membranes
Published on: July 19, 2022
Lipid mobility controls the diffusion of small biopolymer adsorbates
Chakradhar Padala1, Richard Cole, Sanat Kumar
1Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 26, 2006
Summary
This study experimentally verifies that adsorbed DNA on lipid bilayers diffuses like a polymer within a 2D fluid. DNA's movement quantitatively matches the underlying lipid bilayer's mobility, confirming polymer dynamics in two dimensions.
Area of Science:
- Biophysics
- Polymer Science
- Membrane Biophysics
Background:
- Studies suggest adsorbed polymers on lipid bilayers behave like polymers in a 2D fluid.
- This hypothesis lacked direct experimental verification.
- Understanding polymer dynamics in two dimensions is crucial for various biological and material science applications.
Purpose of the Study:
- To experimentally test the conjecture that strongly adsorbed polymers on supported lipid bilayers behave as if in a 2D fluid.
- To investigate the dynamics of short DNA oligonucleotides adsorbed on cationic lipid bilayers.
- To gain insights into polymer diffusion in two-dimensional systems.
Main Methods:
- Designed an experimental protocol involving the lateral transport of single-stranded DNA on a supported cationic lipid bilayer.
- Utilized Fluorescence Recovery After Photobleaching (FRAP) analysis to measure diffusion coefficients.
- Varied experimental conditions, such as temperature, to alter bilayer mobility.
Main Results:
- The diffusivity of adsorbed DNA quantitatively tracked the lateral mobility of the underlying lipid bilayer.
- This correlation held true even when bilayer mobility changed by two orders of magnitude with temperature variations.
- Results for short, extended biopolymers mirrored those of globular proteins in lipid bilayers.
Conclusions:
- Short macromolecules strongly adsorbed on lipid bilayers can be effectively treated as macromolecules within the bilayer.
- The experimental findings support the model of adsorbed polymers behaving as if in a 2D fluid.
- This study provides quantitative evidence for polymer dynamics in two-dimensional fluidic environments.
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...
01:12Diffusion
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...
01:21Diffusion
Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
01:26Membrane Fluidity
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.
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is a relatively...
Mosaic nature of the membrane
The mosaic characteristic of the membrane helps the plasma membrane remain fluid. The integral proteins and lipids exist as separate but loosely-attached molecules in the membrane. The membrane is a relatively...
01:23Membrane Fluidity
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.Fatty acids tails of phospholipids can be either saturated or...
01:17Passive Diffusion: Overview and Kinetics
Passive diffusion is a critical process that allows small lipophilic drugs to cross the cell membrane along a concentration gradient. This mechanism's efficiency depends on four primary factors: the membrane's surface area, the drug's lipid-water partition coefficient, the concentration gradient, and the membrane's thickness.
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...