Supramolecular Association Impacts Biomolecule Adsorption onto Goethite

Area of Science:

• Environmental chemistry
• Biochemistry
• Soil science

Background:

• Mineral-stabilized organic matter formation is crucial for soil carbon sequestration.
• Understanding dissolved organic matter (DOM) interactions with minerals is key to soil organic matter dynamics.
• The impact of biomolecule supramolecular association on mineral adsorption is understudied.

Purpose of the Study:

• To investigate how supramolecular complexation of deoxyribonucleic acid (DNA) and bovine serum albumin (BSA) affects their adsorption onto goethite.
• To elucidate the role of DNA-BSA interactions in governing interfacial behavior and mineral adsorption.
• To explore the implications for understanding mineral retention of DOM in soil.

Main Methods:

• Synthesis and characterization of DNA-BSA supramolecular complexes at varying BSA concentrations.
• Adsorption experiments of DNA-BSA complexes onto goethite at pH 5.0.
• Techniques included circular dichroism, dynamic light scattering, electrophoretic mobility, and spectroscopic studies.

Main Results:

• DNA and BSA form strong supramolecular complexes, with DNA saturation observed around 0.4 mg/mL BSA.
• DNA-BSA complexation reduces electrostatic repulsion between DNA molecules, enhancing adsorption up to 0.4 mg/mL BSA.
• Higher BSA concentrations (>0.4 mg/mL) decreased DNA adsorption, likely due to surface site blocking by loosely bound BSA.

Conclusions:

• Supramolecular interactions significantly alter the interfacial behavior and mineral adsorption of biomolecules.
• The study reveals a complex relationship between biomolecule concentration, complexation, and mineral surface interactions.
• Solution-phase interactions and supramolecular complexation are critical, yet often overlooked, factors in the mineral retention of DOM in soils.