Adsorption of biomolecule-rich supramolecular complexes onto mineral surfaces plays an important role in the development of organo-mineral associations in soils. In this study, a series of supramolecular complexes of a model nucleic acid (deoxyribonucleic acid (DNA)) and protein (bovine serum albumin (BSA)) are synthesized, characterized and exposed to goethite to probe their adsorption behavior. To synthesize DNA/BSA complexes, a fixed DNA concentration (0.1 mg/mL) was mixed with a range of BSA concentrations (0.025-0.5 mg/mL) in 5 mM KCl at pH=5.0. Circular dichroism spectroscopy demonstrates strong binding between DNA and BSA, with DNA saturation achieved when BSA concentration reaches 0.4 mg/mL. Dynamic light scattering measurements suggest BSA binding to DNA reduces DNA-DNA intermolecular repulsion, resulting in a decrease of the DNA slow relaxation mode with increasing amount of BSA. Zeta potential measurements show increasing amounts of BSA lead to lower negative charge on DNA/BSA complexes, corresponding with light scattering results. <i>In-situ </i>infrared spectroscopic studies of adsorption of DNA/BSA complexes onto goethite show that complexation of BSA with DNA appears to hinder coordination of DNA backbone phosphodiester groups with goethite, relative to DNA alone. Furthermore, increasing BSA (up to 0.4 mg/mL) in DNA/BSA complexes enhances DNA adsorption, possibly the result of reduced repulsion between adsorbed DNA helices. When BSA concentration exceeds 0.4 mg/mL, a decrease in adsorbed DNA is observed. We hypothesize this discrepancy between systems with BSA concentrations below and above saturation of DNA is caused by initial fast adsorption of loosely associated BSA on goethite, restricting access of DNA/BSA complexes to goethite surface sites. Overall, results highlight the impact of solution interaction between biomolecules on subsequent behavior at mineral surfaces. This work represents a bridge between model experiments with individual biomolecules and more complex natural systems, yielding a fundamental viewpoint of the formation of organo-mineral associations in soils. <br/>

Adsorption of nucleic acid/protein supramolecular complexes on goethite: Impact of solution interactions on behavior at the solution-mineral interface

255th National Meeting (2018)

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