Related Experiment Video
Updated: Jun 27, 2026
10:37
Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Equilibrium cluster formation in concentrated protein solutions and colloids.
Anna Stradner1, Helen Sedgwick, Frédéric Cardinaux
1Department of Physics, University of Fribourg, Chemin du Musée 3, CH-1700 Fribourg, Switzerland.
Nature
|November 27, 2004
Summary
Controlling particle interactions is key in many fields. This study shows that combining short-range attraction with long-range repulsion in protein and colloid-polymer systems leads to small, stable clusters.
Area of Science:
- Soft matter physics
- Colloid science
- Biophysics
Background:
- Controlling interparticle interactions, aggregation, and cluster formation is crucial in diverse fields, including disease processes, protein crystallography, and photonic crystal production.
- Recent advances in understanding short-range attractive potentials in colloidal systems have revealed phenomena like liquid-liquid phase separation and dynamically arrested states (attractive/repulsive glasses, transient gels).
- The glass paradigm has been applied to complex soft matter, yet cluster phase formation remains an intriguing challenge.
Purpose of the Study:
- To investigate the formation of equilibrium clusters in model protein solutions and colloid-polymer mixtures.
- To understand the role of combined short-range attraction and long-range repulsion in these systems.
- To explore the implications of cluster formation for nucleation, self-assembly, and colloidal suspensions.
Main Methods:
- Small-angle scattering (SAS) investigations.
- Confocal microscopy studies.
- Analysis of two model systems: protein solutions and colloid-polymer mixtures.
Main Results:
- Demonstrated the formation of small equilibrium clusters in both protein solutions and colloid-polymer mixtures.
- Showed that a combination of short-range attraction and long-range repulsion drives this cluster formation.
- Identified these clusters as a key factor in nucleation and self-assembly processes.
Conclusions:
- The interplay of short-range attraction and long-range repulsion is a fundamental mechanism for forming small equilibrium clusters.
- This finding has significant implications for protein crystallization, protein/DNA self-assembly, and understanding cluster/gel phases in colloidal systems.
Related Concept Videos
02:18The Equilibrium Binding Constant and Binding Strength
The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at equilibrium:
02:18The Equilibrium Binding Constant and Binding Strength
The equilibrium binding constant (Kb) quantifies the strength of a protein-ligand interaction. Kb can be calculated as follows when the reaction is at equilibrium:
01:17Colloids and Suspensions
Children at play often make suspensions such as mixtures of mud and water, flour and water, or a suspension of solid pigments in water known as tempera paint. These suspensions are heterogeneous mixtures composed of relatively large particles visible to the naked eye or seen with a magnifying glass. They are cloudy, and the suspended particles settle out after mixing. The suspended particles in a suspension settle out after some time of mixing. The separation of particles from a suspension is...
01:09Colloidal precipitates
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
01:06Coagulation
Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
01:29The Colloidal State
The formation of a colloidal system is exemplified by an aqueous solution containing Cl− ions is introduced to another containing Ag+ ions, resulting in the precipitation of solid AgCl as extremely tiny crystals. Instead of settling out as a filterable precipitate, these crystals remain suspended in the liquid, showcasing a colloidal system.A colloidal system involves colloidal particles within the approximate range of 1 to 1000 nm in at least one dimension, dispersed in a medium called the...