Inst. Chemie

837 Items

Recent Submissions
Kooperative Bindungsaktivierung von Al–H- und Sn–H-Bindungen in Hydroalanen bzw. -stannanen für die Katalyse

Forster, Francis (2019)

Die vorliegende Dissertation widmet sich der kooperativen Bindungsaktivierung von E–H-Bindungen (E = R2Al, R3Sn, R3Ge) an den polaren Ru–S-Bindungen von Ohki–Tatsumi-Komplexen sowie dem Einsatz der somit erzeugten schwefelstabilisierten Hauptgruppenelektrophile in der Katalyse. Die Aktivierung der Al–H-Bindung in DIBAL–H an den Ruthenium(II)-Thiolaten lieferte die entsprechenden Hydroalanaddu...

Synthesis, characterization, and crystal structure of aqua­bis­­(4,4′-dimeth­­oxy-2,2′-bi­pyridine)[μ-(2R,3R)-tartrato(4−)]dicopper(II) octa­hydrate

Wiedemann, Dennis ; Kulko, Roman-David ; Grohmann, Andreas (2019-06-11)

Typical electroless copper baths (ECBs), which are used to chemically deposit copper on printed circuit boards, consist of an aqueous alkali hydroxide solution, a copper(II) salt, formaldehyde as reducing agent, an L-(+)-tartrate as complexing agent, and a 2,2′-bi­pyridine derivative as stabilizer. Actual speciation and reactivity are, however, largely unknown. Herein, we report on the synthesi...

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...

Untersuchungen zur Züchtung von CuAlO2-Einkristallen

Wolff, Nora (2019)

Die vorliegende Arbeit entstand während meiner Tätigkeit als wissenschaftliche Mitarbeiterin am Leibniz-Institut für Kristallzüchtung in Berlin. Das Ziel der Arbeit war Bedingungen zu definieren, unter denen CuAlO2-Einkristalle aus dem Eigenfluss gezüchtet werden können. Zusätzlich wurden Untersuchungen zum Mischkristallsystem CuAlO2-CuFeO2 gemacht. Mithilfe thermodynamischer Messungen (DTA-TG)...

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...

Computational Aminoacyl-tRNA Synthetase Library Design for Photocaged Tyrosine

Baumann, Tobias ; Hauf, Matthias ; Richter, Florian ; Albers, Suki ; Möglich, Andreas ; Ignatova, Zoya ; Budisa, Nediljko (2019-05-11)

Engineering aminoacyl-tRNA synthetases (aaRSs) provides access to the ribosomal incorporation of noncanonical amino acids via genetic code expansion. Conventional targeted mutagenesis libraries with 5–7 positions randomized cover only marginal fractions of the vast sequence space formed by up to 30 active site residues. This frequently results in selection of weakly active enzymes. To overcome ...

In-Cell Synthesis of Bioorthogonal Alkene Tag S-Allyl-Homocysteine and Its Coupling with Reprogrammed Translation

Nojoumi, Saba ; Ma, Ying ; Schwagerus, Sergej ; Hackenberger, Christian P. R. ; Budisa, Nediljko (2019-05-09)

In this study, we report our initial results on in situ biosynthesis of S-allyl-l-homocysteine (Sahc) by simple metabolic conversion of allyl mercaptan in Escherichia coli, which served as the host organism endowed with a direct sulfhydration pathway. The intracellular synthesis we describe in this study is coupled with the direct incorporation of Sahc into proteins in response to methionine co...

Precious metal-free bifunctional catalysts for reversible seawater electrolyzers

Dresp, Sören (2019)

Regenerative hydrogen, which is produced by renewable electricity used in water electrolyzers, is considered as ideal energy carrier of the future. The selective splitting of seawater into oxygen and hydrogen seem to be a promising alternative compared to established water electrolysis technologies, which typically use highly purified water and electrolytes only. In addition, the back transform...

Über die Stabilität von stromlosen Kupferbädern und die stabilisierende Wirkung des Azins 2,2'-Bipyridin

Kulko, Roman-David (2019)

Die vorliegende Arbeit beschreibt die Untersuchung der unspezifische Kupferabscheidung, UKA, in dem stromlosen Kupferabscheidungsprozess, der zur spezifischen Kupferabscheidung, SKA, von metallischem Kupfer in chemischen Kupferbädern, CKB, auf den elektrischen Strom nichtleitenden Substraten u.a. in der Fertigung von Leiterplatten genutzt wird. Hierzu wird eine einfache aber effektive Methode z...

Pulsed laser deposition of efficient ternary metal oxide photoelectrodes

Kölbach, Moritz (2019)

Climate change, mainly driven by the combustion of fossil fuels releasing the greenhouse gas CO2, is a major threat to humanity and the ecosystems on our planet. To limit global warming, a transition towards a sustainable energy infrastructure based on renewable energies is essential. The storage of solar energy in the form of chemical bonds, in so-called solar fuels, is thereby believed to be ...

Promotion of the collagen triple helix in a hydrophobic environment

Kubyshkin, Vladimir ; Budisa, Nediljko (2019-02-06)

In contrast to many other water-soluble peptide arrangements, the formation of a triple helix in collagen proceeds inside out: polar glycyl residues form the interior, whereas nonpolar prolyl side chains constitute the exterior. In our work, we decided to exploit this aspect of the peptide architecture in order to create hyperstable collagen mimicking peptides (CMPs). The key element of this st...

Synthesis of N-heterocycles from diamines via H2-driven NADPH recycling in the presence of O2

Al-Shameri, Ammar ; Borlinghaus, Niels ; Weinmann, Leonie ; Scheller, Philipp N. ; Nestl, Bettina M. ; Lauterbach, Lars (2019-01-23)

Herein, we report an enzymatic cascade involving an oxidase, an imine reductase and a hydrogenase for the H2-driven synthesis of N-heterocycles. Variants of putrescine oxidase from Rhodococcus erythropolis with improved activity were identified. Substituted pyrrolidines and piperidines were obtained with up to 97% product formation in a one-pot reaction directly from the corresponding diamine s...

Catalytic hydrogenation of α,β-unsaturated carboxylic acid derivatives using copper(i)/N-heterocyclic carbene complexes

Zimmermann, Birte M. ; Kobosil, Sarah C. K. ; Teichert, Johannes F. (2019-01-28)

A simple and air-stable copper(I)/N-heterocyclic carbene complex enables the catalytic hydrogenation of enoates and enamides, hitherto unreactive substrates employing homogeneous copper catalysis and H2 as a terminal reducing agent. This atom economic transformation replaces commonly employed hydrosilanes and can also be carried out in an asymmetric fashion.

Untersuchungen zur Biosynthese von Omphalotin

Ramm, Sascha (2019)

Originally discovered in 1987, Omphalotin is an undodecapeptide (which is) synthesized by the basidiomycete Omphalotus olearius. The fungal secondary metabolite shows a strong nematicide and selective activity against the plant parasite Meloidogyne incognita. Structurally, it bears various remarkable characteristics, as for example nine methylations of the α-nitrogen atoms in the peptide backbo...

Commensurate Nb2Zr5O15: Accessible Within the Field Nb2ZrxO2x+5 After All

Wiedemann, Dennis ; Orthmann, Steven ; Mühlbauer, Martin J. ; Lerch, Martin (2019-04-04)

Doped niobium zirconium oxides are applied in field-effect transistors and as special-purpose coatings. Whereas their material properties are sufficiently known, their crystal structures remain widely uncharacterized. Herein, we report on the comparably mild sol–gel synthesis of Nb2Zr5O15 and the elucidation of its commensurately modulated structure via neutron diffraction. We describe the stru...

Structure–Thermodynamic‐Property Relationships in Cyanovinyl‐Based Microporous Polymer Networks for the Future Design of Advanced Carbon Capture Materials

Yassin, Ali ; Trunk, Matthias Georg ; Czerny, Frank ; Fayon, Pierre ; Trewin, Abbie ; Schmidt, Johannes ; Thomas, Arne (2017)

Nitrogen‐rich solid absorbents, which have been immensely tested for carbon dioxide capture, seem until this date to be without decisive molecular engineering or design rules. Here, a family of cyanovinylene‐based microporous polymers synthesized under metal‐catalyzed conditions is reported as a promising candidate for advanced carbon capture materials. These networks reveal that isosteric heat...

Room-Temperature Activation of Hydrogen by Semi-immobilized Frustrated Lewis Pairs in Microporous Polymer Networks

Trunk, Matthias Georg ; Teichert, Johannes F. ; Thomas, Arne (2017)

Porous polymer networks based on sterically encumbered triphenylphosphine motifs, mimicking the basic sites employed in frustrated Lewis pair (FLP) chemistry, were synthesized via Yamamoto polymerization and their interactions with the strong Lewis acid B(C6F5)3 probed. The combinations yield semi-immobilized FLPs, which are able to cleave dihydrogen heterolytically at ambient temperature and l...

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...

Nanostructured porous carbon synthesized from metal-organic precursors as efficient electrochemical catalysts

Li, Shuang (2019)

The development of electrocatalysts for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is of crucial importance to address the global demand for sustainable energy conversion devices with high efficiency, such as fuel cells and metal–air batteries, and the production of hydrogen by electrolysis of water. Nanostructured carbons are pro...