SKM 2023 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 23: Single Molecule Biophysics

BP 23.2: Vortrag

Donnerstag, 30. März 2023, 10:00–10:15, BAR 0106

ion-specific DNA adsorption at mica mediated by monovalent and divalent metal cations — •Ibrahim Mohd, Max Lallemang, Bizan N Balzer, and Nadine Schwierz — University of Augsburg, Germany

Ion mediated attraction between biomolecules and solid substrates plays a crucial role in a broad range of biotechnological applications. In this work, we combine molecular dynamics simulations and single-molecule atomic force microscopy experiments to characterise the desorption properties of single-stranded DNA at mica surface mediated by the alkali and alkaline earth metal ions Li+, Na+, K+, Cs+, Mg2+ and Ca2+. Our results show that both monovalent and divalent ions induce an attractive interaction between DNA and the negatively charged mica surface. DNA adhesion is caused by two effects: Firstly, ion-specific adsorption of the monovalent cations compensates the negative charge and induces a long-ranged attraction. In addition, the surface adsorbed cations form inner-sphere contacts with the oxygen atoms of the DNA backbone. Both effects depend on the type of cation: Cs+ and K+ ions lead to loosely associated DNA with high surface mobility and low rupture forces. Na+, Li+, and divalent ions lead to a stronger association of DNA with low surface mobility and high rupture forces. By comparing the force-extension curve shapes from experiments and simulations we could provide atomistic insights into the desorption mechanisms and identify the dominant interactions involved in the desorption process.