Université de Fribourg

Metal nanoparticle–microbe interactions: synthesis and antimicrobial effects

Khan, Mujeebur R. ; Fromm, Katharina M. ; Rizvi, Tanveer F. ; Giese, Bernd ; Ahamad, Faheem ; Turner, Raymond J. ; Füeg, Michael ; Marsili, Enrico

In: Particle & Particle Systems Characterization, 2020, vol. 37, no. 5, p. 1900419

Metal nanoparticles (NPs), chalcogenides, and carbon quantum dots can be easily synthesized from whole microorganisms (fungi and bacteria) and cell‐free sterile filtered spent medium. The particle size distribution and the biosynthesis time can be somewhat controlled through the biomass/metal solution ratio. The biosynthetic mechanism can be explained through the ion‐reduction theory and...

Université de Fribourg

Metal nanoparticle–microbe interactions: synthesis and antimicrobial effects

Khan, Mujeebur R. ; Fromm, Katharina M. ; Rizvi, Tanveer F. ; Giese, Bernd ; Ahamad, Faheem ; Turner, Raymond J. ; Füeg, Michael ; Marsili, Enrico

In: Particle & Particle Systems Characterization, 2020, vol. 37, no. 5, p. 1900419

Metal nanoparticles (NPs), chalcogenides, and carbon quantum dots can be easily synthesized from whole microorganisms (fungi and bacteria) and cell‐free sterile filtered spent medium. The particle size distribution and the biosynthesis time can be somewhat controlled through the biomass/metal solution ratio. The biosynthetic mechanism can be explained through the ion‐reduction theory and...

Université de Fribourg

Kinetics and mechanism of mineral respiration: how iron hemes synchronize electron transfer rates

Chabert, Valentin ; Babel, Lucille ; Füeg, Michael P. ; Karamash, Maksym ; Madivoli, Edwin S. ; Herault, Nelly ; Dantas, Joana M. ; Salgueiro, Carlos A. ; Giese, Bernd ; Fromm, Katharina M.

In: Angewandte Chemie International Edition, 2020, p. -

Anaerobic microorganisms of the Geobacter genus are effective electron sources for the synthesis of nanoparticles, for bioremediation of polluted water, and for the production of electricity in fuel cells. In multistep reactions, electrons are transferred via iron/heme cofactors of c‐type cytochromes from the inner cell membrane to extracellular metal ions, which are bound to outer membrane...

Université de Fribourg

Amide neighbouring-group effects in peptides: phenylalanine as relay amino acid in long-distance electron transfer

Nathanael, Joses G. ; Gamon, Luke F. ; Cordes, Meike ; Rablen, Paul R. ; Bally, Thomas ; Fromm, Katharina M. ; Giese, Bernd ; Wille, Uta

In: ChemBioChem, 2018, vol. 19, no. 9, p. 922–926

In nature, proteins serve as media for long‐distance electron transfer (ET) to carry out redox reactions in distant compartments. This ET occurs either by a single‐step superexchange or through a multi‐step charge hopping process, which uses side chains of amino acids as stepping stones. In this study we demonstrate that Phe can act as a relay amino acid for long‐distance electron...

Université de Fribourg

Proline as a charge stabilizing amino acid in peptide radical cations

Monney, Nicolas P.-A. ; Bally, Thomas ; Giese, Bernd

In: Journal of Physical Organic Chemistry, 2015, vol. 28, no. 5, p. 347–353

Long distance electron transfer in proteins requires relay stations that can be transitorily oxidized or reduced. Although individual prolines cannot assume this function, because of their high ionization energy, it has been shown that polyprolines have the ability to transfer charges. In order to determine the role of the proline in the hole distribution and transport within a PheProPhe...

Université de Fribourg

Electron transfer in peptides: on the formation of silver nanoparticles

Kracht, Sonja ; Messerer, Matthias ; Lang, Matthieu ; Eckhardt, Sonja ; Lauz, Miriam ; Grobéty, Bernard ; Fromm, Katharina M. ; Giese, Bernd

In: Angewandte Chemie International Edition, 2015, vol. 54, no. 10, p. 2912–2916

Some microorganisms perform anaerobic mineral respiration by reducing metal ions to metal nanoparticles, using peptide aggregates as medium for electron transfer (ET). Such a reaction type is investigated here with model peptides and silver as the metal. Surprisingly, Ag⁺ ions bound by peptides with histidine as the Ag⁺-binding amino acid and tyrosine as photoinducible electron donor cannot...

Université de Fribourg

Fragment orbital based description of charge transfer in peptides including backbone orbitals

Heck, Alexander ; Woiczikowski, P. Benjamin ; Kubař, Tomáš ; Welke, Kai ; Niehaus, Thomas ; Giese, Bernd ; Skourtis, Spiros ; Elstner, Marcus ; Steinbrecher, Thomas B.

In: The Journal of Physical Chemistry B, 2014, vol. 118, no. 16, p. 4261–4272

Charge transfer in peptides and proteins can occur on different pathways, depending on the energetic landscape as well as the coupling between the involved orbitals. Since details of the mechanism and pathways are difficult to access experimentally, different modeling strategies have been successfully applied to study these processes in the past. These can be based on a simple empirical pathway...

Université de Fribourg

Kinetics of ion transport through supramolecular channels in single crystals

Assouma, Cyrille D. ; Crochet, Aurélien ; Chérémond, Yvens ; Giese, Bernd ; Fromm, Katharina M.

In: Angewandte Chemie International Edition, 2013, vol. 52, no. 17, p. 4682–4685

Single-crystal to single-crystal transformations are possible by ion-exchange and transport reactions through supramolecular channels that are composed of crown ether molecules and use trihalide ions as scaffolds. Kinetic measurements of ion transport at different temperatures provide activation energy data and show that a very fast.

Université de Fribourg

Radicals and radical ions as intermediates of electron transfer processes through peptides

Giese, Bernd ; Eckhardt, Sonja ; Lauz, Miriam ; Gao, Jian ; Wang, Min

In: Chimia, 2012, vol. 66, no. 6, p. 364-367

Electron transfer (ET) through peptides and proteins is a key biochemical process, which involves radicals and radical ions as reactive intermediates. We have developed an assay that allows us to study this fundamental chemical reaction.