FG Physikalische Chemie / Biophysikalische Chemie

46 Items

Recent Submissions
Catalytic dioxygen reduction mediated by a tetranuclear cobalt complex supported on a stannoxane core

Chandra, Anirban ; Mebs, Stefan ; Kundu, Subrata ; Kuhlmann, Uwe ; Hildebrandt, Peter ; Dau, Holger ; Ray, Kallol (2020-04-08)

The synthesis, spectroscopic characterization (infrared, electron paramagnetic resonance and X-ray absorption spectroscopies) and density functional theoretical calculations of a tetranuclear cobalt complex Co4L1 involving a nonheme ligand system, L1, supported on a stannoxane core are reported. Co4L1, similar to the previously reported hexanuclear cobalt complex Co6L2, shows a unique ability t...

Hydroxy-bridged resting states of a [NiFe]-hydrogenase unraveled by cryogenic vibrational spectroscopy and DFT computations

Caserta, Giorgio ; Pelmenschikov, Vladimir ; Lorent, Christian ; Waffo, Armel F. Tadjoung ; Katz, Sagie ; Lauterbach, Lars ; Schoknecht, Janna ; Wang, Hongxin ; Yoda, Yoshitaka ; Tamasaku, Kenji ; Kaupp, Martin ; Hildebrandt, Peter ; Lenz, Oliver ; Cramer, Stephen P. ; Zebger, Ingo (2020-12-11)

The catalytic mechanism of [NiFe]-hydrogenases is a subject of extensive research. Apart from at least four reaction intermediates of H2/H+ cycling, there are also a number of resting states, which are formed under oxidizing conditions. Although not directly involved in the catalytic cycle, the knowledge of their molecular structures and reactivity is important, because these states usually acc...

Dihydrogen-driven NADPH recycling in imine reduction and P450-catalyzed oxidations mediated by an engineered O2-tolerant hydrogenase

Preissler, Janina ; Reeve, Holly A. ; Zhu, Tianze ; Nicholson, Jake ; Urata, Kouji ; Lauterbach, Lars ; Wong, Luet L. ; Vincent, Kylie A. ; Lenz, Oliver (2020-06-16)

The O2-tolerant NAD+-reducing hydrogenase (SH) from Ralstonia eutropha (Cupriavidus necator) has already been applied in vitro and in vivo for H2-driven NADH recycling in coupled enzymatic reactions with various NADH-dependent oxidoreductases. To expand the scope for application in NADPH-dependent biocatalysis, we introduced changes in the NAD+-binding pocket of the enzyme by rational mutagenes...

Biochemical and spectroscopic insights into peculiar active site structures and biosynthesis of O2-tolerant [NiFe]-hydrogenases

Schulz, Anne-Christine (2021)

[NiFe]-hydrogenases are metalloenzymes catalyzing the reversible cleavage of H2 into two H+ and two e–. They are particularly interesting for clean and sustainable H2-based energy conversion approaches or the H2-driven regeneration of nucleotide cofactors. Their active site consists of a NiFe(CN)2(CO) moiety coordinated to the protein by four strictly conserved cysteine residues. Two of them se...

The large subunit of the regulatory [NiFe]-hydrogenase from Ralstonia eutropha – a minimal hydrogenase?

Caserta, Giorgio ; Lorent, Christian ; Ciaccafava, Alexandre ; Keck, Matthias ; Breglia, Raffaella ; Greco, Claudio ; Limberg, Christian ; Hildebrandt, Peter ; Cramer, Stephen P. ; Zebger, Ingo ; Lenz, Oliver (2020-04-27)

Chemically synthesized compounds that are capable of facilitating the reversible splitting of dihydrogen into protons and electrons are rare in chemists' portfolio. The corresponding biocatalysts – hydrogenases – are, however, abundant in the microbial world. [NiFe]-hydrogenases represent a major subclass and display a bipartite architecture, composed of a large subunit, hosting the catalytic N...

A membrane‐bound [NiFe]‐hydrogenase large subunit precursor whose C‐terminal extension is not essential for cofactor incorporation but guarantees optimal maturation

Hartmann, Sven ; Frielingsdorf, Stefan ; Caserta, Giorgio ; Lenz, Oliver (2020-03-16)

[NiFe]‐hydrogenases catalyze the reversible conversion of molecular hydrogen into protons end electrons. This reaction takes place at a NiFe(CN)2(CO) cofactor located in the large subunit of the bipartite hydrogenase module. The corresponding apo‐protein carries usually a C‐terminal extension that is cleaved off by a specific endopeptidase as soon as the cofactor insertion has been accomplished...

Powering Artificial Enzymatic Cascades with Electrical Energy

Al‐Shameri, Ammar ; Petrich, Marie‐Christine ; junge Puring, Kai ; Apfel, Ulf‐Peter ; Nestl, Bettina M. ; Lauterbach, Lars (2020-04-28)

We have developed a scalable platform that employs electrolysis for an in vitro synthetic enzymatic cascade in a continuous flow reactor. Both H2 and O2 were produced by electrolysis and transferred through a gas‐permeable membrane into the flow system. The membrane enabled the separation of the electrolyte from the biocatalysts in the flow system, where H2 and O2 served as electron mediators f...

Spectroscopic studies on hydrogenases

Katz, Sagie (2020)

The establishment of sustainable economy may be based on molecular hydrogen as an energy-storage molecule and requires the development of cheap catalysts, which are able to work under various conditions. In nature, this most fundamental reaction, i.e. the reversible reduction of protons, is catalysed by a group of enzymes called hydrogenases. Members of this wide family of enzymes exhibit vario...

Combined vibrational spectroscopy and electrochemistry for studying biological and materials systems

Querebillo, Christine Joy Uy (2020)

In this thesis, combined vibrational spectroscopy and electrochemistry is applied to investigate two different projects in biological and materials sciences. In the biological project on the putative hemoprotein redox sensor MsmS(-sGAF2) from M. acetivorans, resonance Raman (RR) spectroscopy reveals that a six-coordinated low spin (6cLS) and a five-coordinated high spin (5cHS) state is the pre...

X-ray Crystallography and Vibrational Spectroscopy Reveal the Key Determinants of Biocatalytic Dihydrogen Cycling by [NiFe] Hydrogenases

Ilina, Yulia ; Lorent, Christian ; Katz, Sagie ; Jeoung, Jae-Hun ; Shima, Seigo ; Horch, Marius ; Zebger, Ingo ; Dobbek, Holger (2019-10-25)

[NiFe] hydrogenases are complex model enzymes for the reversible cleavage of dihydrogen (H2). However, structural determinants of efficient H2 binding to their [NiFe] active site are not properly understood. Here, we present crystallographic and vibrational‐spectroscopic insights into the unexplored structure of the H2‐binding [NiFe] intermediate. Using an F420‐reducing [NiFe]‐hydrogenase from ...

An Assessment of the Bioactivity of Coffee Silverskin Melanoidins

Tores de la Cruz, Silvia ; Iriondo-DeHond, Amaia ; Herrera, Teresa ; Lopez-Tofiño, Yolanda ; Galvez-Robleño, Carlos ; Prodanov, Marin ; Vélazquez Escobar, Francisco ; Abalo, Raquel ; del Castillo, Maria Dolores (2019-02-12)

Melanoidins present in coffee silverskin, the only by-product of the roasting process, are formed via the Maillard reaction. The exact structure, biological properties, and mechanism of action of coffee silverskin melanoidins, remain unknown. This research work aimed to contribute to this novel knowledge. To achieve this goal, melanoidins were obtained from an aqueous extract of Arabica coffee ...

Spectroscopic investigation of phytochromes and NIR fluorescent variants

Buhrke, David (2019)

In this work, vibrational spectroscopic methods (resonance Raman [RR] and infrared absorption [IR]) were used for the investigation of phytochromes. Phytochromes are bistable photoreceptor proteins that bind bilins (BV, PCB, PΦB) as chromophores. Various plant, cyanobacterial, and bacterial variants regulate biological processes through the light dependent switching between metastable states th...

Studying protein-cofactor complexes: a combined experimental and theoretical approach

Salewski, Johannes (2019)

The majority of enzymes contains one or more organic or inorganic cofactor molecule(s) attached to the protein matrix which enable their respective functions. The interaction between these cofactor molecules and the protein environment is highly specific and determines the structure–function relationship of many enzymes. The work in this thesis utilizes a combination of experimental and theoret...

Electric fields at biomimetic interfaces

Staffa, Jana Katharina (2019)

Electric fields and electrostatic interactions can essentially influence biological processes. This is particularly true for membrane proteins since their activities may be controlled by changes of the transmembrane potential. To elucidate such processes requires appropriate biomimetic membranes, preferentially on electrodes to allow variations of the potential across a bilayer. Particular conv...

Surface functionalised and nanostructured transparent conductive oxides

Harris, Tomos Gwilym Ab Alun (2019)

Storage of (renewable) energy in the form of chemical bonds in electrofuels, their later conversion back to electricity, or the generation of renewable chemical feedstocks from CO2, N2 etc. all require the use of stable and efficient catalysts. In particular, there is urgent need for the development of efficient, precious-metal free catalysts. Enzymes and inorganic (e.g. biomimetic) molecular c...

Competition of Pyridoxal 5'-Phosphate with Ribulose 1,5-Bisphosphate and Effector Sugar Phosphates at the Reaction Centers of the Spinach Ribulose 1,5-Bisphosphate Carboxylase/Oxygenase

Vater, Joachim ; Gaudszun, Thomas ; Scharnow, Harald ; Salnikow, Johann (1980)

The Stimulation of the carboxylase reaction by effectors of ribulose 1,5-bisphosphate carboxyl­ ase/oxygenase displays higher sensitivity towards pyridoxal 5'-phosphate inhibition than the catalytical process itself. Pyridoxal 5'-phosphate binding to the enzyme is not affected by the modulators 6-phospho-gluconate and fructose 1,6-bisphosphate at low concentrations at which these agents stimula...

Oxygen-Evolving Extracts from a Thermophilic Cyanobacterium Synechococcus sp.

Miyairi, Sachio ; Schatz, Günther H. (1983)

Spheroplast membranes of a thermophilic cyanobacterium Synechococcus sp. have been treated with the detergent lauryldim ethylam ine oxide (LDAO). The resulting extracts show (1) light-induced O2 evolution with artificial electron acceptors, (2) four-fold enhancement of the O2 evolution relative to chlorophyll, (3) parallel increase of both the molar ratios of PS 2/C hl and cyt b559/Chl in the e...

Studies on the Functional Mechanism of System II Herbicides in Isolated Chloroplasts

Renger, Gernot ; Hagemann, A. ; Vermaas, Wim F.J. (1984)

The effect of specific proteolytic enzymes on variable fluorescence, p-benzoquinone-mediated oxygen evolution, PS II herbicide (atrazine and bromoxynil) binding, and protein degradation has been analyzed in isolated class II pea chloroplasts. It was found that: 1. Trypsin and a lysine-specific protease effectively reduce the maximum chlorophyll-a fluorescence yield, whereas the initial fluoresc...

Herbicide/Quinone Binding Interactions in Photosystem II

Vermaas, Wim F.J. ; Renger, Gernot ; Arntzen, Charles J. (1984)

Many inhibitors prevent the oxidation of the primary electron-accepting quinone (QA) by the secondary quinone (Qв) in photosystem II by displacement of Qв from its binding site. On the other hand, plastoquinone-1 and 6-azido-5-decyl-2,3-dim ethoxy-p-benzoquinone displace herbicides. Binding studies show the herbicide/quinone interaction to be (apparently) competitive.The herbicide binding is in...

Structure of the ATP-Synthase from Chloroplasts and Mitochondria Studied by Electron Microscopy

Boekema, Egbert J. ; Schmidt, Günter ; Gräber, Peter ; Berden, Jan A. (1988)

The structure of the ATP-synthase, F0F1 , from spinach chloroplasts and beef heart mitochondria has been investigated by electron microscopy with negatively stained specimens. The detergent-solubilized ATP-synthase forms string-like structures in which the F0 parts are aggregated. In most cases, the F, parts are arranged at alternating sides along the string. The F0 part has an approximate cyli...