Using the Radial Distribution Function to Analyze Atomic Force Microscopy Images of Colloidal Systems

Area of Science:

• Colloid and Surface Science
• Nanotechnology
• Biophysics

Background:

• Biomacromolecules function in aqueous environments, but their behavior in solution is challenging to study directly.
• Investigating molecules adsorbed on 2D surfaces offers insights into their 3D solution states.
• Atomic force microscopy (AFM) requires immobilizing nanosized objects for study.

Purpose of the Study:

• To determine if surface-adsorbed biomolecule structure properties reflect their 3D colloidal solution state.
• To analyze the structural organization of immobilized gold nanoparticles (AuNPs) and horseradish peroxidase (HRP) on mica.
• To apply radial distribution function (RDF) methods to assess order in immobilized particle arrangements.

Main Methods:

• Atomic Force Microscopy (AFM) for imaging immobilized nanoparticles and molecules.
• Radial Distribution Function (RDF) analysis to quantify particle arrangement and order.
• Immobilization of gold nanoparticles (AuNPs) and horseradish peroxidase (HRP) on mica surfaces.

Main Results:

• Gold nanoparticles (AuNPs) exhibit mobility on mica in the presence of water.
• Immobilized AuNPs form amorphous structures with evident short-range order.
• Horseradish peroxidase molecules adsorb randomly, with surface density following a Poisson distribution.

Conclusions:

• Surface immobilization and RDF analysis can provide insights into the structural properties of colloidal systems.
• The behavior of AuNPs on a surface differs from their behavior in bulk solution.
• Protein adsorption patterns can be statistically described, indicating random surface distribution.