DNA binding to mica correlates with cationic radius: assay by atomic force microscopy

Area of Science:

• Biophysics
• Materials Science
• Nanotechnology

Background:

• Atomic Force Microscopy (AFM) allows high-resolution imaging of biological molecules.
• Understanding DNA-surface interactions is crucial for nanotechnology and molecular biology.
• Mica is a common substrate for AFM studies due to its atomically flat surface.

Purpose of the Study:

• To investigate the effect of transition metal cations on DNA binding to mica.
• To correlate cation properties with the strength of DNA-mica adhesion.
• To establish an AFM-based assay for DNA-surface interactions.

Main Methods:

• DNA immobilization on mica in buffers containing various transition metal salts.
• Imaging of DNA-mica complexes using Atomic Force Microscopy (AFM).
• Analysis of DNA binding strength based on AFM imaging quality and cation properties (ionic radius, hydration enthalpy).

Main Results:

• DNA binds effectively to mica with Ni(II), Co(II), and Zn(II) cations (ionic radii 0.69–0.74 Å).
• DNA binding is weaker with Mn(II) (0.82 Å) and negligible with Cd(II) (0.97 Å) and Hg(II) (1.1 Å).
• Optimal DNA binding occurs at approximately 1-mM concentrations of Ni(II), Co(II), or Zn(II); Mg(II) does not promote sufficient binding for AFM imaging.

Conclusions:

• The ionic radius and hydration enthalpy of transition metal cations significantly influence DNA binding to mica.
• AFM imaging provides a sensitive method to quantify DNA-surface interactions mediated by cations.
• This AFM assay has potential applications for studying polymer-surface binding phenomena.