Browsing by Subject "Binding"

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    Monitoring molecular assembly of biofilms using quartz crystal microbalance with dissipation
    (Springer, 2022) Yuca, E.; Şeker, Urartu Özgür Şafak; Arluison, Véronique; Wien, Frank; Marcoleta, Andrés
    The structure and the functionality of biofilm proteins, the main components of the extracellular matrix, can be tuned by protein engineering. The use of binding kinetics data has been demonstrated in the characterization of recombinantly produced biofilm proteins to control their behavior on certain surfaces or under certain conditions. Quartz crystal microbalance with dissipation monitoring (QCM-D) allows measuring the change in resonance frequency and the energy loss and distribution upon the interaction of molecules with the surface. The characterization of the molecular assembly of curli biofilm proteins on different surfaces using QCM-D is presented here as a detailed protocol. The experimental procedure detailed in this chapter can be applied and modified for other biofilm proteins or subunits to determine their surface adsorption and kinetic binding characteristics.
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    X-ray-induced production of gold nanoparticles on a SiO2/Si system and in a poly(methyl methacrylate) matrix
    (American Chemical Society, 2005) Karadas, F.; Ertas, G.; Ozkaraoglu, E.; Süzer, Şefik
    Prolonged exposure to X-rays of HAuCl4 deposited from an aqueous solution onto a SiO2/Si substrate or into a poly(methyl methacrylate) (PMMA) matrix induces reduction of the Au3+ ions to Au0 and subsequent nucleation to gold nanoclusters as recorded by X-ray photoelectron spectroscopy. The corresponding major oxidation product is determined as chlorine {HAuCl4(ads) + X-rays -Au(ads) + (3/2)Cl 2(ada) + HCl(ads)}, which is initially adsorbed onto the surface but eventually diffuses out of the system into the vacuum. The reduced gold atoms aggregate (three-dimensionally) into gold nanoclusters as evidenced by the variation in the binding energy during X-ray exposure, which starts as 1.3 eV but approaches a value that is 0.5 eV higher than that of the bulk gold. The disappearance of the oxidation product (Cl2p signal) and the growth of the nanoclusters (related to the measured binding energy difference between the Si2p of the oxide and Au4f of the reduced gold) exhibit first-order kinetics which is approximately 3 times slower than the reduction of Au3+, indicating that both of the former processes are diffusion controlled. Similarly, gold ions incorporated into PMMA can also be reduced and aggregated to gold nanoclusters using 254 nm deep UV irradiation in air evidenced by UV - vis - NIR absorption spectrocopy.