Recent publications
Overview of our 100 most recent publications registered in Cristin:
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Gerz, Isabelle; Aunan, Erlend ; Finelli, Valeria; Abu Rasheed, Mouhammad; Deplano, Gabriele & Cortez Sgroi Pupo, Rafael
[Show all 15 contributors for this article]
(2024).
Enabling a bioinspired N,N,N-copper coordination motif through spatial control in UiO-67: synthesis and reactivity.
Dalton Transactions.
ISSN 1477-9226.
doi:
10.1039/d3dt03096b.
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Austrheim, Håkon Olaf; Hu, Depan; Ulven, Ole Ivar & Andersen, Niels Højmark
(2024).
Formation of Natural Magnesium Silica Hydrate (M-S-H) and Magnesium Alumina Silica Hydrate (M-A-S-H) Cement.
Materials.
ISSN 1996-1944.
17(5).
doi:
10.3390/ma17050994.
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Kneiding, Hannes; Nova Flores, Ainara & Balcells Badia, David
(2024).
Directional multiobjective optimization of metal complexes at the billion-system scale.
Nature Computational Science.
ISSN 2662-8457.
doi:
10.1038/s43588-024-00616-5.
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Brugger, Melanie; Lauri, Antonella; Zhen, Yan; Gramegna, Laura L.; Zott, Benedikt & Sekulic, Nikolina
[Show all 40 contributors for this article]
(2024).
Bi-allelic variants in SNF8 cause a disease spectrum ranging from severe developmental and epileptic encephalopathy to syndromic optic atrophy.
American Journal of Human Genetics.
ISSN 0002-9297.
111(3),
p. 594–613.
doi:
10.1016/j.ajhg.2024.02.005.
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Coggon, Matthew M.; Stockwell, Chelsea E.; Claflin, Megan S.; Pfannerstill, Eva Y.; Xu, Lu & Gilman, Jessica B.
[Show all 24 contributors for this article]
(2024).
Identifying and correcting interferences to PTR-ToF-MS measurements of isoprene and other urban volatile organic compounds.
Atmospheric Measurement Techniques.
ISSN 1867-1381.
17(2),
p. 801–825.
doi:
10.5194/amt-17-801-2024.
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Corrales, Jeanne; Ramos Alonso, Lucia; González-Sabín, Javier; Ríos-Lombardía, Nicolás; Trevijano-Contador, Nuria & Berg, Henriette Engen
[Show all 12 contributors for this article]
(2024).
Characterization of a selective, iron-chelating antifungal compound that disrupts fungal metabolism and synergizes with fluconazole.
Microbiology spectrum.
ISSN 2165-0497.
12(2).
doi:
10.1128/spectrum.02594-23.
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Wanniarachchi, Chapa; Eidsvåg, Håkon; Arunasalam, Thevakaran; Ravirajan, Punniamoorthy; Velauthapillai, Dhayalan & Ponniah, Vajeeston
(2024).
Deep insight into structural and optoelectronic properties of mixed anion perovskites.
Materials Research Express.
ISSN 2053-1591.
11(2).
doi:
10.1088/2053-1591/ad1f98.
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Yuste-Tirados, Irene; Liu, Xin; Kjølseth, Christian & Norby, Truls
(2024).
Boundaries of DC operation of a tubular proton ceramic electrochemical reactor with BZCY electrolyte and Ni-BZCY cermet electrodes.
Journal of Power Sources.
ISSN 0378-7753.
596.
doi:
10.1016/j.jpowsour.2024.234097.
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Gkatzelis, Georgios I.; Coggon, Matthew M.; Stockwell, Chelsea E.; Hornbrook, Rebecca S.; Allen, Hannah & Apel, Eric C.
[Show all 65 contributors for this article]
(2024).
Parameterizations of US wildfire and prescribed fire emission ratios and emission factors based on FIREX-AQ aircraft measurements.
Atmospheric Chemistry and Physics (ACP).
ISSN 1680-7316.
24(2),
p. 929–956.
doi:
10.5194/acp-24-929-2024.
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Attallah, Mohamed F.; Elchine, Dominik; Grödler, Dennis; Margreiter, Raphael; Maslo, Melisa & Michel, Marco
[Show all 9 contributors for this article]
(2024).
Trace-scale extraction of carrier-free tungsten radioisotope as a homolog of Sg using ionic liquid from acid solutions: Kinetic study.
Separation and Purification Technology.
ISSN 1383-5866.
331.
doi:
10.1016/j.seppur.2023.125418.
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Pedersen, Thomas Bondo; Lehtola, Susi; Galván, Ignacio Fdez. & Lindh, Roland
(2024).
The versatility of the Cholesky decomposition in electronic structure theory.
Wiley Interdisciplinary Reviews. Computational Molecular Science.
ISSN 1759-0876.
14(1).
doi:
10.1002/wcms.1692.
Full text in Research Archive
Show summary
The resolution-of-the-identity (RI) or density fitting (DF) approximation for the electron repulsion integrals (ERIs) has become a standard component of accelerated and reduced-scaling implementations of first-principles Gaussian-type orbital electronic-structure methods. The Cholesky decomposition (CD) of the ERIs has also become increasingly deployed across quantum chemistry packages in the last decade, even though its early applications were mostly limited to high-accuracy methods such as coupled-cluster theory and multi-configurational approaches. Starting with a summary of the basic theory underpinning both the CD and RI/DF approximations, thus underlining the extremely close relation of the CD and RI/DF techniques, we provide a brief and largely chronological review of the evolution of the CD approach from its birth in 1977 to its current state. In addition to being a purely numerical procedure for handling ERIs, thus providing robust and computationally efficient approximations to the exact ERIs that have been found increasingly useful on modern computer platforms, CD also offers highly accurate approaches for generating auxiliary basis sets for the RI/DF approximation on the fly due to the deep mathematical connection between the two approaches. In this review, we aim to provide a concise reference of the main techniques employed in various CD approaches in electronic structure theory, to exemplify the connection between the CD and RI/DF approaches, and to clarify the state of the art to guide new implementations of CD approaches across electronic structure programs.
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Sannes, Johnny Andreas & Valldor, Björn Martin
(2023).
Sr<inf>2</inf>Te<inf>4</inf>V<inf>2</inf>O<inf>13</inf>Cl<inf>2</inf>, a Layered Structure Forming a Canted Antiferromagnetic Ground State.
Chemistry of Materials.
ISSN 0897-4756.
35(5),
p. 2355–2362.
doi:
10.1021/acs.chemmater.3c02961.
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Montserrat Canals, Mateu; Bjerregaard-Andersen, Kaare; Vinther Sørensen, Henrik; Cordara, Gabriele; Vaaje-Kolstad, Gustav & Krengel, Ute
(2023).
Calcium binding site in AA10 LPMO from Vibrio cholerae suggests modulating effects during environment survival and infection.
bioRxiv.
ISSN 2692-8205.
doi:
10.1101/2023.12.22.573012.
Full text in Research Archive
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Nagpal, Harsh; Ali Ahmad, Ahmad; Hirano, Yasuhiro; Cai, Wei; Halic, Mario & Fukagawa, Tatsuo
[Show all 8 contributors for this article]
(2023).
CENP-A and CENP-B collaborate to create an open centromeric chromatin state.
Nature Communications.
ISSN 2041-1723.
14(1).
doi:
10.1038/s41467-023-43739-5.
Full text in Research Archive
Show summary
Centromeres are epigenetically defined via the presence of the histone H3 variant CENP-A. Contacting CENP-A nucleosomes, the constitutive centromere associated network (CCAN) and the kinetochore assemble, connecting the centromere to spindle microtubules during cell division. The DNA-binding centromeric protein CENP-B is involved in maintaining centromere stability and, together with CENP-A, shapes the centromeric chromatin state. The nanoscale organization of centromeric chromatin is not well understood. Here, we use single-molecule fluorescence and cryoelectron microscopy (cryoEM) to show that CENP-A incorporation establishes a dynamic and open chromatin state. The increased dynamics of CENP-A chromatin create an opening for CENP-B DNA access. In turn, bound CENP-B further opens the chromatin fiber structure and induces nucleosomal DNA unwrapping. Finally, removal of CENP-A increases CENP-B mobility in cells. Together, our studies show that the two centromere-specific proteins collaborate to reshape chromatin structure, enabling the binding of centromeric factors and establishing a centromeric chromatin state.
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Holmsen, Marte Sofie Martinsen; Nova Flores, Ainara & Tilset, Mats
(2023).
Cyclometalated (N,C) Au(III) Complexes: The Impact of Trans Effects on Their Synthesis, Structure, and Reactivity.
Accounts of Chemical Research.
ISSN 0001-4842.
56(24),
p. 3654–3664.
doi:
10.1021/acs.accounts.3c00595.
Full text in Research Archive
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Balakrishnan, Kanimozhi; Veerapandy, Vasu & Ponniah, Vajeeston
(2023).
The optical properties and spectroscopic limited maximum efficiency of SnO<inf>2</inf> polymorphs for solar cell applications: A first-principles analysis.
Computational condensed matter.
ISSN 2352-2143.
37.
doi:
10.1016/j.cocom.2023.e00856.
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Ganesan, Kalaiselvan; Ponniah, Vajeeston; Yao, Jiyong; Vohra, Yogesh K. & Sonachalam, Arumugam
(2023).
Appearance of semiconductor-to-metal transition in Ba<inf>2</inf>BiFeSe<inf>5</inf> single crystal: A combined DFT and transport analysis under pressure.
Journal of Materials Research.
ISSN 0884-2914.
doi:
10.1557/s43578-023-01235-y.
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Wanniarachchi, Chapa; Arunasalam, Thevakaran; Ravirajan, Punniyamoorthy; Velauthapillai, Dhayalan & Ponniah, Vajeeston
(2023).
Hybrid Functional Study on Electronic and Optical Properties of the Dopants in Anatase TiO<inf>2</inf>.
ACS Omega.
ISSN 2470-1343.
8(45),
p. 42275–42289.
doi:
10.1021/acsomega.3c04329.
Full text in Research Archive
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Pagonis, Demetrios; Selimovic, Vanessa; Campuzano-Jost, Pedro; Guo, Hongyu; Day, Douglas A. & Schueneman, Melinda K.
[Show all 29 contributors for this article]
(2023).
Impact of Biomass Burning Organic Aerosol Volatility on Smoke Concentrations Downwind of Fires.
Environmental Science and Technology.
ISSN 0013-936X.
57(44),
p. 17011–17021.
doi:
10.1021/acs.est.3c05017.
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Kneiding, Hannes; Nova Flores, Ainara & Balcells Badia, David
(2023).
Directional Multiobjective Optimization of Metal Complexes at the Billion-Scale with the tmQMg-L Dataset and PL-MOGA Algorithm.
ChemRxiv.
ISSN 2573-2293.
doi:
10.26434/chemrxiv-2023-k3tf2-v2.
Show summary
Transition metal complexes (TMCs) play a key role in several areas of high interest, including medicinal chemistry, renewable energies, and nanoporous materials. The development of TMCs enabling these technologies remains challenged by the need to optimize multiple properties within very large chemical spaces, in which the thirty transition metals can be combined with a virtually infinite number of ligands. In this work, we provide the open tmQMg-L dataset including 30K TMC ligands, which combines large chemical diversity with synthesizability. The charge and metal-coordination mode of the ligands were robustly defined with a novel algorithm based on graph and natural bond orbital theories. The tmQMg-L dataset was leveraged in the automated generation of 1.37M TMCs resulting from all possible combinations between a square planar palladium(II) scaffold and a pool of 50 different ligands. This TMC space was used to benchmark a multiobjective genetic algorithm (MOGA) that optimized two properties over a Pareto front; namely the polarizability (alpha) and the HOMO-LUMO gap (epsilon). The MOGA evolved 130 TMC hits with maximal (alpha, epsilon) values in a way that could be easily rationalized by analyzing the nature of the ligands selected. Instead of the traditional mutation and crossover of fragments within a single ligand, this MOGA implemented full-ligand genetic operations acting on all coordination sites, maximizing chemical diversity. Further, we extended this MOGA algorithm with the Pareto-Lighthouse functionality (PL-MOGA), which allows for controlling both the aim and scope of the multiobjective optimization over the Pareto front. In explicit spaces containing billions of TMCs, the PL-MOGA enabled the explainable generation of thousands of novel and highly diverse TMC hits. We believe that the combined use of the tmQMg-L dataset and PL-MOGA algorithm will facilitate the discovery of TMCs with optimal properties within untapped chemical spaces.
View all works in Cristin
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Wragg, David Stephen; Wachs, Israel E.; Bañares, Miguel A. & Svelle, Stian
(2023).
Springer Handbook of Advanced Catalyst Characterization.
Springer.
ISBN 978-3-031-07125-6.
5(1).
1117 p.
View all works in Cristin
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Wang, Luyang; Sun, Xinwei; Jiang, Bo & Norby, Truls
(2024).
Minority bulk and surface proton conduction in ceramic positrodes for proton ceramic electrochemical cells.
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Montserrat Canals, Mateu; Sekulic, Nikolina & Krengel, Ute
(2024).
UiO structural biology core facilities.
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Brennhagen, Anders; Skurtveit, Amalie; Skautvedt, Casper; Cavallo, Carmen; Wragg, David Stephen & Vajeeston, Ponniah
[Show all 9 contributors for this article]
(2024).
Revealing the (de)sodiation mechanisms of Bi-metallates through operando X-ray characterisation.
Show summary
Na-ion batteries is entering the battery market as an alternative to Li-ion batteries. To improve their overall performance it is crucial to develop new types of anode materials with high capacity and long cycle life. Materials combing conversion and alloying mechanisms (CAMs) are promising anodes with their high capacity, but obtaining good cycling stability is still challenging. A comprehensive understanding of the cycling and degradation mechanism of these materials is crucial to improve their performance.
Bi-metallates, with a general formula of Bi−TM−O (TM = transition metal) is a group of ternary CAMs. Their general cycling mechanism consists of an irreversible conversion reaction forming nanoparticles of Bi-metal embedded in a Na-TM-O matrix during the first sodiation, followed by a reversible two-step alloying reaction forming Na3Bi with NaBi as an intermediate phase. In this work, we have used operando X-ray diffraction (XRD), pair distribution function (PDF) analysis and X-ray absorption spectroscopy (XAS) to investigate the desodiation mechanisms of Bi2MoO6 and BiFeO3.
Through this work, we discovered that Bi2MoO6 forms the cubic version of Na3Bi (c-Na3Bi) while BiFeO3 forms hexagonal Na3Bi (h-Na3Bi) in addition to c-Na3Bi during the first sodiation. In the desodiated state, the Bi-particles are partially oxidised, while still maintaining the Bi-metal structure, indicating that it is only the Bi atoms at the interface between the Bi nanoparticles and the Na−TM−O matrix that is oxidised. During cycling the NaxBi particles grow larger thus increasing the distance between them and increasing the impedance in the material. This is considered to be the main driver for the capacity degradation that was observed during the first 20 cycles. The operando XAS data also revealed that Mo6+ in Bi2MoO6 does not change oxidation state during cycling, but changes coordination between tetrahedral and distorted octahedral coordination during cycling. The cycling and degradation mechanisms of Bi2MoO6 is summarised in Figure 1.
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Nardini, Greta; Liland, Kristian Hovde; Afseth, Nils Kristian & Kristoffersen, Kenneth Aase
(2024).
Classical chromatographic methods and spectroscopic methods – different approaches for protein analysis.
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Wiik, Halfdan; Tveitdal, Svein & Seip, Hans Martin
(2024).
Klima: Har kongen rett eller Braanen.
Klassekampen.
ISSN 0805-3839.
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Montserrat Canals, Mateu; Schnelle, Kilian; Leipart, Vilde; Halskau, Øyvind; Amdam, Gro Vang & Moeller, Arne
[Show all 8 contributors for this article]
(2023).
The high-resolution cryo-EM structure of vitellogenin from the hemolymph of the honey bee.
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Burnage, Arron Luc; Kneiding, Hannes; Nova, Ainara & Balcells, David
(2023).
A 3-Dimentional Search for a Pd Cross-Coupling Catalyst for the Suzuki-Miyaura Reaction
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Svelle, Stian; Lundegaard, Lars Fahl; Beato, Pablo & Wragg, David Stephen
(2023).
Case Studies: Crystallography as a Tool for Studying Methanol Conversion in Zeolites,
Springer Handbook of Advanced Catalyst Characterization.
Springer.
ISSN 978-3-031-07125-6.
p. 541–563.
doi:
10.1007/978-3-031-07125-6_26.
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Roen, Stine; Norby, Truls; Strandbakke, Ragnar & Polfus, Jonathan M.
(2023).
Electrochemical characterization of Ba0.95La0.05(Fe0.7Ni0.2Zn0.1)O3-δ for proton ceramic electrochemical cells.
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Seip, Hans Martin
(2023).
Klimaendringer og virkelighet.
Klassekampen.
ISSN 0805-3839.
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Seip, Hans Martin
(2023).
Klimaendringer: Tvilsom teori.
Klassekampen.
ISSN 0805-3839.
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Seip, Hans Martin & Wiik, Halfdan
(2023).
INP: Et understatement.
Klassekampen.
ISSN 0805-3839.
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Seip, Hans Martin & Wiik, Halfdan
(2023).
Klima og solidaritet.
Klassekampen.
ISSN 0805-3839.
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Gudmundsdottir, Jonina Björg; Vøllestad, Einar; Haugsrud, Reidar & Polfus, Jonathan
(2023).
Oxygen Exchange Kinetics of BaGd0.3La0.7Co2O6-d.
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Bjørnestad, Victoria Ariel & Lund, Reidar
(2023).
Surfactant micelles and structural pathways for solubilization of lipid membranes.
u.
ISSN 1501-7710.
2023(2603).
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Hempel, Frida Sveen & Fjellvåg, Helmer
(2023).
Substituted Na-based Layered Tellurates: Synthesis, Local Structure and Na-Dynamics.
University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Chemistry.
ISSN 1501-7710.
2023(2688).
Show summary
Solid-state batteries are currently limited by low ionic conductivity compared to the liquid analogue, and improving ionic conductivity is a major concern for commercialization. This thesis focuses on the local structure and ionic conductivity mechanism of a solid-state electrolyte candidate (the layered oxide Na2Zn2TeO6). The Na content of layered materials is well known to influence conductivity and phase stability, and in this work this is changed by substituting the framework cations Zn and Te with Ga and Sb.
The first work of this thesis establishes a reliable synthesis route for the substituted materials, ensuring and confirming homogeneous distribution of the substituent by nuclear magnetic resonance spectroscopy (NMR). The decreased Na content is found to increase local motion of Na, but this is not translated to long range motion of ionic conductivity. Decreasing the Na-content is therefore not enough to improve ionic conductivity.
This work finally made an in-depth study of complex ordering schemes that may occur in multicomponent layered oxides. The real situation can indeed be very complex, compared to the rather simple average picture description.
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Ofstad, Benedicte Sverdrup & Kvaal, Simen
(2023).
Time-domain quantum dynamics: Optical properties from time-dependent electronic-structure theory.
University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Chemistry.
ISSN 1501-7710.
2023(2689).
Show summary
Within the field of nonlinear optics, nonlinear optical properties are defined as frequency-dependent responses. This definition emerged in the frequency domain, as lasers used in these early experiments emitted monochromatic continuous waves. This led to the development of time-dependent electronic-structure theory predominantly in the frequency domain, using perturbation-theory based response theory. However, in recent years, advances in computing power and the advent of ultrashort laser pulses have sparked interest in the time-domain for both electronic-structure theory and nonlinear optics. Time-domain electronic-structure theory provides a time-resolved description of light-matter interaction, closely mimicking experiment. Additionally, they offer the advantage of highly nonlinear responses being straightforward to implement.
This thesis contributes to the field of time-domain time-dependent electronic-structure theory for the description of nonlinear optical properties by: Investigating the potential of dynamic (time-dependent) orbitals for improving the description of nonlinear optical properties, extending a hierarchy of time-domain time-dependent coupled-cluster methods to accommodate strong magnetic fields, and by developing an efficient approach for extracting higher-order response properties.
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Kvande, Karoline & Svelle, Stian
(2023).
Compositional and Mechanistic Studies of Cu-zeolites for the Direct Activation of Lower Alkanes.
University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Chemistry.
ISSN 1501-7710.
2023(2633).
Show summary
Due to poor access and energy-intensive conversion reactions, large reservoirs of natural gas are underutilized. Natural gas and biogas mainly contain small and stable hydrocarbons (light alkanes) and could be a more sustainable resource in the nearest future for the chemical industry, compared to coal and oil. However, due to the stability of alkanes, it is notoriously difficult to make specific products, because, in a reaction, the products are usually more reactive, and unwanted by-products are formed. With the help of activity testing and multiple characterization techniques, we have obtained insight into a direct, but stepwise pathway to convert alkanes to functionalized products for the industry that is potentially less energy-demanding than the existing ones. The stepwise pathway proceeds over oxidized Cu ions anchored to porous materials (zeolites) that hinder the reactants and products from interacting. With this approach, there is almost no over-oxidation, although, the product yield per time from this reaction is low. Accordingly, our focus has been on exploring different parts of the reaction to understand the individual steps and how they can be improved. We have obtained more insight into the Cu speciation and found important activity relationships with both zeolite structure and Cu ion reducibility.
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Crapart, Camille Marie & Vogt, Rolf David
(2023).
Origin and Fate of Dissolved Organic Matter in Boreal Lakes Under the Environmental Changes of the 21st Century.
University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Chemistry.
ISSN 1501-7710.
2023(2684).
Show summary
Surface water in the Nordic countries, a crucial resource, has been undergoing a noticeable browning trend over recent decades due to increased dissolved organic matter (DOM), originating from microscopic residues of living organisms. This dissertation delves into three key aspects of this phenomenon.
Firstly, a comprehensive dataset spanning Norway, Sweden and Finland was used to investigate the relative contribution of various factors to this browning. Acid deposition of sulfur and nitrogen in the 60-70s had resulted in a decrease of DOM concentration. While nitrogen deposition still plays a role nowadays, vegetation growth has a larger positive effect. Predictions based on climatic scenarios foresee a continued rise in DOM.
Secondly, the study focuses on the fate of DOM in lakes, where microorganisms consume it. The rate of microbial respiration was measured. This highlighted that the DOM originating from lakes surroundings, particularly hard to degrade, stimulates microbial respiration, releasing CO2. Nitrogen availability, however, constrains this process.
The high DOM concentration in lakes is linked to CO2 emissions. In Norway, where lakes are small and clear, lakes contribute little to the national carbon budget. In Sweden and Finland, however, lakes might release carbon equivalent to the amount stored by forests.
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Panfilov, Daniil & Monakhov, Eduard
(2023).
Fabrication and characterisation of 4H-SiC diodes for particles detectors.
Kjemisk Institutt, Universitetet i Oslo.
Show summary
Silicon Carbide (SiC) radiation detectors are increasingly gaining recognition for their enhanced performance in diverse applications including nuclear radiation detection, functioning under high-temperature environments, x-ray detection, neutron detection and dosimetry. SiC comes out on top with its ability to operate efficiently in challenging environments. Compared to its primary competitor silicon (Si), 4H-SiC polytype has higher thermal conductivity, superior temperature stability, and a wider bandgap. In this thesis a scalable fabrication technique for n-type 4H-SiC Schottky diodes is proposed, serving as a stepping stone for the future fabrication of 4H-SiC-based detectors. The work encompasses the development and fine-tuning of photolithography processes, fabrication of 4H-SiC Schottky diodes, and their characterization. The photolithography process is based on the lift-off method. It involves two layers: (i) positive resist and (ii) a so-called lift-off layer to provide an undercut for easier removal of the resist. Such parameters as the exposure and development times were optimized. Optical microscopy and cross-sectional scanning electron microscopy were employed for optimizing the lithography process. Nickel, deposited by e-beam evaporation, was used for formation of Schottky diodes. Current-Voltage (IV) measurements show that the reverse-bias leakage current for most of the diodes is below the detection limit of the instruments used. The reverse saturation currents and the ideality factors are deduced from the fitting of the diode equation to the measurements for the forward bias. The lowest ideality factor and saturation current are 1.14 and 3.24∗10−21𝐴, respectively. The highest breakdown voltage obtained is 350 V. Capacitance-Voltage (CV) measurements have revealed the doping concentration in the epi-layer to be 1.2−1.3∗1016 𝑐𝑚−3. The depletion width at 100 V is deduced to be around 3 μm. The highest built-in voltage is found to be 1.6 V for 200 μm diodes, which is comparable with a theoretic value of 1.7 V. It is observed that smaller diodes (200 μm) demonstrate better characteristics, such as ideality factor, breakdown voltage and build-in voltage, compared to larger ones (2000 μm). We hypothesise that this is due to surface imperfections in the SiC epi-layer or dust particles from poor sample handling: As the diode size increases, there is a higher probability of a surface imperfection or a dust particle to occur between SiC and the metal, which will be detrimental for the Schottky diode. CV characterization of metal-oxide-semiconductor (MOS) structures is used to examine thermally grown silicon oxide (𝑆𝑖𝑂2) and aluminium oxide (𝐴𝑙2𝑂3), deposited by atomic layer deposition (ALD). MOS with thermally grown 𝑆𝑖𝑂2 reveal CV curves typical for a high-quality MOS structure, validating the insulating and passivating properties of the oxide. In comparison, ALD-grown 𝐴𝑙2 𝑂3 did not manifest reproducible and consistent CV characteristics.
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Nguyen, Hao Pierre Quoc & Prytz, Øystein
(2023).
Structural and Chemical Characterization of ZnGe_xSn_(1-x)N_2 for Solar Cell Applications.
Kjemisk Institutt, Universitetet i Oslo.
Show summary
Nitride semiconductors possess a variety of properties, such as a high dielectric breakdown voltage and bandgap energies ranging from ultraviolet to infrared, favorable for scientific development and application in efficient tandem solar cells. The ideal bandgap for top cells has been calculated to be ∼ 1.75 eV in combination with Si bottom cells, in a two-terminal device. However, some challenges related to materials phase separation and lattice mismatch, as well as cost barriers related to the choice of rare materials and initial growth process, pose problems for consumer implementation. Thin films of ZnGexSn1−xN2 (where x = 0, 0.428 or 0.736) were grown on P:ZnO by reactive co-sputtering of metallic Zn, Sn and Ge targets employing high-power impulse magnetron sputtering (HiPIMS) and conventional RF sputtering. These materials were selected due to their earth-abundance and non-toxic properties. Structural properties were characterized by electron diffraction (ED) and chemical properties were analyzed with energy dispersive X-ray spectroscopy (EDS), both in transmission electron microscopy (TEM). In the present work, high resolution TEM and ED were used in combination to study the atomic structure and strain effects of thin films, which were grown along the [001] direction, perpendicular to the surface of the substrate, and a higher applied Ge target power predictably yields a higher Ge incorporation. A higher Ge content in the alloy is found to produce a more polycrystalline structure, in comparison to pristine ZnSnN2. Additionally, ED indicates that the film structure without Ge has a significant lattice mismatch with the ZnO substrate (a = (0.336 ± 0.004) nm for ZnSnN2, a = (0.319 ± 0.001) nm for ZnO, mismatch ∼ 5.3%) and the induced strain is relaxed through formation of misfit dislocations. In contrast, films with higher Ge incorporation (a = (0.328 ± 0.005) nm for x = 0.74, a = (0.331 ± 0.005) nm for x = 0.43) exhibit a better lattice matching with the substrate (a = (0.326 ± 0.001) nm for ZnO, mismatch ∼ 0.6% and ∼ 1.2% respectively).
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Krogseth, Ola Bohne & Lund, Reidar
(2023).
The Effect of Antimicrobial Peptides on Ion Transport in Model Membranes.
Kjemisk Institutt, Universitetet i Oslo.
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This thesis delves into the ion transport mechanisms of antimicrobial peptides through lipid membranes, examining the effects of peptide and saline concentrations on membrane properties such as structure, shape, and response to osmotic shock. To gain a comprehensive understanding, three distinct experimental approaches were utilized: scattering, electrophysiology, and imaging techniques. The work focus on using simple models roughly mimicking the negative surface of Gram-negative bacterial lipid membranes. These are used to decipher the ion transport capabilities of antimicrobial peptides and their ability in mitigating osmotic shock. Using an electrophysiology technique, specifically suspended planar lipid bilayers, allowed a direct method of detecting ion perturbations through the membrane upon peptide addition. The establishment of a suspended planar lipid bilayer lab, in addition to the development of a consistent protocol for producing functional lipid films, were essential to this research. The findings indicate that the peptide gramicidin forms a membrane-spanning pore, facilitating ion transport. Furthermore, it was found that indolicidin, another peptide, may appear to be involved in an ion-carrying mechanism. Additionally, the thesis demonstrate that small unilamellar liposomes containing water have a structural change under varying saline concentrations, which might be counterbalanced by the introduction of antimicrobial peptides. This discovery and further research could shed light on the capacity of peptides to transport ions across the membrane and alleviate osmotic pressure. This work employed small-angle X-ray scattering in tandem with electron microscopy and dynamic light scattering to explore the morphological changes of liposomes experiencing osmotic pressure. This investigation revealed the size and morphological alterations in liposomes was induced by osmotic pressure. It was found that osmotic shock causes liposomes to transition into a bilamellar structures. This morphological change was found to be alleviated through the ion transport facilitated by antimicrobial peptides.
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van Hooft, Jessie & Wisthaler, Armin
(2023).
Plume Chemistry Simulations with the SCICHEM Model.
Kjemisk Institutt, Universitetet i Oslo.
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Amine-based post-combustion carbon capture is a method used for reducing CO2 emissions from industrial point sources. During this process, amines can be released into the environment and form carcinogenic nitrosamines and nitramines. Consequently, the location where it is safe to build carbon capture facilities depends on the levels of carcinogens, and where in the atmosphere they are formed. In this project, power plant plume fields simulated using the plume chemistry model SCICHEM were compared to published results obtained with the Fluidity-Chem model. Following this, SCICHEM was used to understand the influence of the atmospheric chemical background, the applied atmospheric chemistry scheme and NO emission strength on the chemical evolution of an isolated ship plume. Subsequently, NO, NO2, O3 and OH fields were simulated after NO emission from a hypothetical Waste-to-Energy plant using SCICHEM, first without and later with the emission of the amine piperazine. It was found that SCICHEM cannot simulate plume edge details well, thereby emphasizing the need for more detailed models like the Volumetric Particle Approach model, currently under development at NILU, that was also tested for comparison. Moreover, the application of different chemistry schemes was found to lead to different results. Processes such as ozone titration, HNO3 formation and HONO formation, should be included in the chemistry scheme. The atmospheric chemical background and especially the peroxy radicals therein, e.g. HO2 and CH3C(O)O2, were found to play an important role in OH depletion or formation close to the source. Under low NO emission (i.e. 3.02 g/s), the conventional conception of OH being depleted near the source was found not to be valid. On the contrary, the OH chemistry starts close to the source, resulting in OH formation beginning at 2 km downwind from the source. As a result, piperazine nitrosamine and nitramine levels were found to be highest close to the source. With an emission of 0.032 g/s of piperazine, maximum nitrosamine and nitramine concentrations of 0.97 ng/m3 and 0.72 ng/m3, respectively, were found at surface level approximately 1 to 1.5 km downwind from the source. In the case of additional direct nitrosamine emission, the nitrosamine level increased to up to 1.54 ng/m3 close to the source. Higher NO emissions of 30.2 g/s were found to lower the nitrosamine and nitramine concentrations, and shift the maximum concentration further downwind from the source due to increased OH depletion. Meteorological parameters and background conditions were simplified and kept constant throughout the entire run, which is not realistic. Therefore, improved simulations should be performed using varying background and meteorological conditions that are valid for the locations of interest.
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Midtøy, Lise & Røberg-Larsen, Hanne
(2023).
Evaluation of sample preparation methods for protein analysis of liver organoids.
Kjemisk Institutt, Universitetet i Oslo.
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For mass spectrometry (MS)-based proteomics, different sample preparation methods were evaluated for limited cell samples (10 000-200 000 cells), and the optimized method was used to analyze liver organoids (20-30 organoids, equivalent to approximately 50 000 cells). The sample preparation methods evaluated were urea-based in-solution-digestion (ISD-Urea), a detergent-free sample preparation method named sample preparation by easy extraction and digestion (SPEED), and a method with bead-based sample clean-up called single-pot, solid-phase enhanced sample preparation (SP3). The samples were analyzed with liquid chromatography (LC)-MS using a nanoLC column or a micropillar array column coupled to a trapped ion mobility time of flight (timsTOF)-MS. The samples prepared by SPEED had the overall highest number of protein identifications among all the sample sizes, with a range of 1684-3503 proteins identified for 10 000-100 000 cells. A quantification method for estimation of protein yield was found difficult, but because of the superior performance regarding number of protein identifications, SPEED was chosen as method for analyzing liver organoids of different metabolic states using label-free-quantification. The results showed significant differences between the organoid samples, with many of the hypothesized protein profiles found. The number of protein identifications was in the range of 2140-3203 proteins for the samples consisting of 20-30 organoids each. The method was successfully implemented as a preliminary step for disease studies, e.g. non-alcoholic fatty liver disease (NAFLD).
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Amoakwah, Melchizedek & Amedjkouh, Mohamed
(2023).
Synthesis and structural characterization of heteroleptic dipyridophenazine–based [Cu(N^N)(P^P)]+ complexes.
Kjemisk Institutt, Universitetet i Oslo.
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For the purposes of solar–induced multi–electron storage and charge transfer reactions, heteroleptic [Cu(N^N)(P^P)]+ type copper(I) complexes where (N^N)= diimine ligand and (P^P)= bulky diphosphine ligand, have become promising and viable alternatives to noble metal photosensitizers. In this thesis, the synthesis, structural and geometrical configurations of a series of electron–withdrawing para–substituted dipyrido–[3, 2–a: 2’, 3’–c]phenazine(dppz) copper complexes (inclusive of the non-substituted) are studied. With bromo, cyano and 4-methoxycarbonyl nitrophenyl as the substituents and (9,9-Dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane) (xantphos), 1,1'-Bis (diphenylphosphino)ferrocene (dppf) and ([1,1′-Binaphthalene]-2,2′ diyl)bis(diphenylphosphane) (binap) as the (P^P) ligands, the corresponding complexes were synthesized via a one–pot two–step method and characterized using multinuclear NMR, DOSY, FTIR and UV–Vis DR spectroscopy. The dppz ligands were obtained in quantitative yields via bromination, cyanation and Suzuki–type coupling reactions conducted on an intermediate benzothiadiazole scaffold. The cyano and alkyl benzoate derivatives were chosen for the prospective aim of incorporating the complexes into Zr–based MOFs UiO–66 and UiO–68 respectively. The free bromo– and cyano–dppz ligands exhibited severe solubility issues, with NMR characterization being possible upon strong acid addition. The complexes showed satisfying stability upon exposure to air and water with DOSY studies in N–donor solvents showing the fortunate absence of dissociative speciation and ligand exchange reactions leading to the formation of homoleptic species. Through–space correlations and solid– state structures defined by NOESY/ROESY NMR and SC–XRD indicated π–stacking properties among the complexes caused by a distorted tetrahedral coordination sphere around the Cu(I) metal. From the UV-Vis DRS studies, it was inferred that the presence of parasubstituted EWGs on the distal benzenoid ring promoted red-shifting of the absorption properties for both the ligands and complexes within the visible region.
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Davidov, Aleksandar; Kvaal, Simen & Balcells, David
(2023).
Improving semiempirical quantum chemistry with graph neural networks.
Kjemisk Institutt, Universitetet i Oslo.
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Betten, Jørn Eirik & Balcells, David
(2023).
Application of Machine Learning in Chemical Space: Machine Learning Methods Applied to Autocorrelation Vectors Generated from the Vaska’s Space Dataset.
Kjemisk Institutt, Universitetet i Oslo.
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The field of chemistry is increasingly applying machine learning methods to aid in the exploration and understanding of the chemical space. This thesis explores a set of supervised machine learning (ML) methods consisting of multi-layer perceptron (MLP) models, Gaussian processes (GPs), multi-layer perceptrons models with a Gaussian process at the output layer (FEGP), and deep Gaussian processes (DGPs) and their performance against the predictions of the DFT-calculated activation barrier associated with the activation of dihydrogen and the H – H bond distance in the transition state to a constructed chemical space surrounding Vaska’s complex. From graph representations of the molecules in this space autocorrelation vectors were provided using generic and electronic property sets for the atoms and bonds in the graph representation. Gradient boosting regressors (GBR) were employed to assess the relevance of each descriptor in the autocorrelation vectors with great success, increasing the interpretability of, in addition to reducing the computational costs associated with, the ML methods. For the prediction of the activation barrier the GP model yielded the lowest mean absolute errors on test sets of 0.75 ± 0.03 kcal/mol, and for the prediction of the H – H distance of the transition state we found that the GBR method outperformed the ML methods, with a mean absolute error of 0.0161 Å.
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Teigland, Eirik Gresaker & Fægri, Karoline
(2023).
Utvikling av undervisningsopplegg; Overvåkning av estersyntese ved bruk av Vernier mini gasskromatograf.
Kjemisk Institutt, Universitetet i Oslo.
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Vernier har en mini gasskromatograf som er utviklet for bruk i undervisning. Mini gasskromatografen er solgt til en god del videregående skoler i Norge. Det finnes noen laboratorieforsøk på norsk som er utviklet for instrumentet, men det er et behov for flere undervisningsopplegg der instrumentet brukes. Målet med dette prosjektet var derfor å lage et undervisningsopplegg med bruk av Vernier mini gasskromatograf som kunne knyttes til flere kompetansemål i den nye læreplanen i kjemi 2. Det ble tatt utgangspunkt i et laboratorieforsøk fra Verniers forsøkssamling om overvåking av en estersyntese. Forsøket ble videreutviklet ved å redusere reaksjonstiden for å kutte ned på tidsbruk. Forsøket ble også gjort mer brukervennlig ved å gjøre produktdannelsen mer repeterbar og ved å øke antallet mulige utgangsstoffer. Det ble utviklet en prelab for å forberede elevene i forkanten av laboratorieøkten og en rapportmal til etterarbeidet. Forsøket ble testet ut på studenter i et kjemididaktikkemne på universitetet. Utprøvingen viste at alle studentene klarte å gjennomføre syntesen, og bruke mini gasskromatografen til å overvåke estersyntesen innenfor en tidsramme på 90 minutter. Studentene opplevde prelabben som nyttig ved at den var relevant og gjorde dem forberedt til forsøket. Studentene mente også at bruken av mini gasskromatografen gav en merverdi til forsøket. Videre arbeid er å justere forsøket slik at det også fungerer med den nye mini gasskromatograf modellen, Go Direct, som har en annen kolonne og detektor enn modellen brukt i denne utviklingen.
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Jalal Ali, Lelaw & Lund, Reidar
(2023).
Delivering antimicrobial peptides through polymer complexation – creating efficient nanocarriers to fight resistant bacteria.
Kjemisk Institutt, Universitetet i Oslo.
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Because of the limited number of antibiotics available and the similarities in their activity and mode of action, considerable nonclinical and clinical research is being spent in the discovery and development of new and non-conventional anti-infective medicines. Interestingly, the polymyxins have piqued the interest of researchers as promising new antibiotics to control infectious pathogens arising from MDR Gram-negative bacteria. In reality, only a few polymyxins have been utilized in “real-world” application, with the most clinically relevant being colistin. While efficacious in the clinical setting, there were subsequent studies that reported severe toxicities with use of colistin as a therapeutic option, especially nephrotoxicity and neurotoxicity as uncommon adverse event The disadvantages associated with colistin can be mitigated by encapsulating the peptide in nanocarriers like block copolymer micelles. However, there is a scarcity when it comes to core-shell assemblies by peptide-polymer conjugates, and in particular the assemblies of peptides assembled with neutral-polyanion DHBC. Moreover, the relation between the release of the peptide and the nanocarrier structure and dynamics is lacking. Therefore, the overall aim of the research presented in this thesis was to develop novel nanomedicines based on the peptide colistin. This includes a systematically investigation of the phase diagram of colistin/PEO-b-PMAA mixtures as a function of pH, charge ratio and total concentration. The overall goal will be to find optimal conditions under which stable core-shell colistin-polymer complexes are formed. In the second part of the project, different formulations of colistin-polymer nanoparticles where investigated in vitro for their bacterial killing activity against few multidrug-resistant Gram-negative bacteria isolates, which were compared to that of free colistin.
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Fredbo, Kamilla Farbrot & Fægri, Karoline
(2023).
Utvikling og utprøving av et undervisningsopplegg i kjemi 2: en undersøkelse av elevers anvendelse av redoksreaksjoner og grønn kjemi knyttet til forsøket «syntese og farging med indigo».
Kjemisk Institutt, Universitetet i Oslo.
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Denne oppgaven omhandler en studie hvor forsøket «syntese og farging med indigo» ble testet på kjemi 2 elever. Forsøket tar for seg redoksreaksjonen av indigo og farging av handlenett med den selvlagde indigoen. Studiet tar utgangspunkt i kompetansemål fra kjemi 2 og den overordnede delen av den nye læreplanen LK20 med særlig fokus på redoksreaksjoner, grønn kjemi, anvendt kjemi, praksiser og tenkemåter i kjemi og bærekraft. Elevene som deltok i studien utførte en prelab øvelse, selve forsøket og besvarte en labrapport. Resultatene knyttet til redoksreaksjonen tyder på at elevene hadde en forståelse ovenfor temaet både før og etter forsøket. Resultater tilknyttet grønn kjemi viste at elevene i stor grad knyttet relevante prinsipper til forsøket, men med ulik grad av begrunnelse for valg av prinsipp. Undervisningsopplegget er i en utviklingsprosess, og flere av spørsmålene fra prelab og rapportmalen kan spesifiseres ytterligere etter ønsket læringsmål. Opplegget har dermed forbedringspotensial på flere områder.
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Mors, Mira & Cascella, Michele
(2023).
Molecular Modeling of Nucleosome Core Particles.
Kjemisk Institutt, Universitetet i Oslo.
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Nucleosomes, the basic units of chromatin in eukaryotes, play a critical role in DNA processing such as transcription, replication, and repair. The canonical nucleosome core particle consists of 145 to 147 DNA base pairs wrapped around a histone octamer composed of one (H3-H4)₂ tetramer and two H2A-H2B dimers. This arrangement results in two stacked disks. Although the importance of non-canonical structures with alternative histone conformations in controlling genome organization and regulation has been recognized, our knowledge of them remains limited. In a recent development, unconventional nucleoprotein particles composed of only two types of histones (H3-H4 or CENP-A-H4) have been identified through cryo-electron microscopy. Here, all-atom molecular dynamics simulations are performed on single nucleosome units to elucidate the specific dynamic properties of the octamers forming a di-tetrameric core. The analysis shows that these structures exhibit significant DNA unwrapping compared to the canonical nucleosome. In particular, the histone H3 variant CENP-A, which marks the location of the centromere, shows the most excessive unwrapping of DNA ends from the core, resulting in an almost orthogonal arrangement of the DNA entry/exit sites. The pronounced flexibility for the last ∼ 20 base pairs observed in the simulations is related to the increased interdisk spacing of the DNA superhelical gyres, which is about one and a half times larger than in the corresponding nucleosome core particle with histones H3 or CENP-A. The results consistently indicate that the di-tetrameric stoichiometry of H3-H4 or CENP-A-H4 leads to increased dynamics and to an opening of the core particle, potentially allowing greater access to DNA binding factors.
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Austenaa, Bjørn Terjei & Amedjkouh, Mohamed
(2023).
Synthesis and characterization of photosensitive ligand for copper complexation and functionalization of UiO-67 MOF.
Kjemisk Institutt, Universitetet i Oslo.
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Denne masteroppgaven beskriver syntese og karakterisering av lysfølsomme ligander for metall kompleks og funksjonalisering av MOF. Oppgaven beskriver vellykket syntese av 2 ligander og et forsøk på et tredje. Det tredje ligandet ville hatt et forlenget pi-system sammenlignet med de to første. For å lage dette ble det forsøkt å sette på et alkyn i en Sonogashira reaksjon. Ligander og mellomprodukter ble karakterisert med NMR spektroskopi og massespektrometri analyse. Smeltepunkter ble også målt for de fleste mellomprodukter og ligandene.
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Falao, Eirik & Krengel, Ute
(2023).
Studies of interaction between the Vibrio cholerae colonization factor GbpA and chitin using NMR spectroscopy and electron microscopy imaging.
Kjemisk Institutt, Universitetet i Oslo.
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he bacterium Vibrio cholerae is one of the most well-known contaminants of water and food sources across the world, and a cause of the disease cholera. It is particularly notorious for having outbreaks in underdeveloped parts of the world, or in areas affected by natural disasters or war, where access to clean drinking water is poor. Each year, cholera is estimated to cause 100 000 deaths. In addition to having the ability to colonize the human intestine, V. cholerae is known to colonize surfaces containing the polysaccharide chitin, found in the exoskeletons of several marine invertebrates. Colonization is believed to involve the adhesin N-acetyl glucosamine binding protein A (GbpA), which V. cholerae secretes into its aquatic environment. GbpA is a multifunctional protein with four domains, three of which have previously been structurally determined by x-ray crystallography. These are the N-terminal domain (D1), and the two middle domains (D2-3). D1 belongs to a class of enzymes called lytic polysaccharide monooxygenase (LPMO), which are known to cleave polysaccharides like chitin or cellulose. This domain is also known to interact with mucins, which are glycoproteins found in the human intestine. The functions of D2 and D3 are not known, but it has been hypothesized that they may play a role in anchoring V. cholerae to its substrate. The structure of the small C-terminal domain (D4) remains unknown, but it has been reported to also bind to chitinous surfaces. This thesis presents the results of interaction studies on GbpA with chitin, carried out by nuclear magnetic resonance (NMR) spectroscopy and electron microscope (EM) imaging. GbpA was produced using VmaxTM as an expression host. VmaxTM is a strain of Vibrio natriegens and a non-toxic relative of V. cholerae, possessing similar secretion pathways useful for GbpA expression and functionality. VmaxTM has previously been shown to express GbpA in high yields, which was confirmed in in this thesis. GbpA was also isotope-labelled with nitrogen-15 (15N) for NMR spectroscopy experiments. Although the NMR experiments yielded some inconclusive results, interactions between chitin and GbpA could be clearly observed in the EM-images obtained. Additionally, D4 was expressed alone with a glutathione S-transferase (GST) tag, using both Escherichia coli and VmaxTM as expression hosts. Although D4 was successfully isolated, extensive optimization of expression is required to acquire sufficient yields for v structure determination by NMR spectroscopy. An alternative method for isolating D4 was tested, where cleavage sites for TEV and HRV 3C proteases were inserted into the flexible linker separating D3 and D4, which would allow for GbpA to be expressed in high yields, from which D4 would be separated. Unfortunately, these cleavage sites could not be recognized by the proteases used, even though the same proteases could successfully cleave other proteins possessing the same cleavage sites. Predictions of the three-dimensional fold of D4 was made using AlphaFold and RoseTTAFold.
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Rønningen, Mats Aksnes & Bonge-Hansen, Tore
(2023).
Utviklingen av synteseruter for multifunksjonelle polymerer rettet mot kreftbehandling.
Kjemisk Institutt, Universitetet i Oslo.
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Dagens gullstandard for kjemoteraputiske legemidler er monoklonale antistoffer (mABS) og antistoff-legemiddel-konjugater (ADC) som selektivt gjenkjenner kreftceller. Antistoffer kan ofte være temperatur sensitive, det kan være vanskelig å kontrollere konjugeringsgrad, samt tidkrevende og kostbare å produsere. Småmolekylære forbindelser, derimot, kan ha affiniteten til kreftceller i mindre grad sammelignet med antistoffer. Dette kan kompenserers for ved å bruke flere småmolekylære forbindelser i samme makromolekylet, ved å danne multivalente bindinger istedet for monovalente som er standarden i dagens legemiddelindustri. Målsettningen for oppgaven var å utvikle en enkel, robust og skalerbare syntesemetode for biokompatible, multifunksjonelle polymere med småmolekylære forbindelser. Dette ble gjort ved å identifisere ulike biologiske småmolekyler med affinitet og selektivitet mot kreftceller. Søket konkluderte med ulike karbohydrater, peptider og naturstoffer, som ved enkle syntetiske grep ble omgjort til acyleringsagenter med aktive estere, hvor utbyttet varierte. Deretter gjennomgikk de aktive esterene reaksjon med polyetylenimin (PEI) for å danne poly(oxazoline)(POx)-produkter med varierende utbytte, som ble bekreftet med ninhydrintest, ESI-Q-TOF-MS, FTIR og NMR undersøkelser. Resultatene ble sammenlignet mot annen litteraturverdier, men fremviste at POx-produktene ble syntetisert på forgrenet PEI istedet for lineær.
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Dirdal, Ragnhild Elise & Omtvedt, Jon Petter
(2023).
Selective Recovery of Copper from Municipal Solid Waste Incineration Bottom Ash.
Kjemisk Institutt, Universitetet i Oslo.
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A hydrometallurgical process was investigated as a method to selectively recover copper from municipal solid waste incineration (MSWI) bottom ash. In Norway, bottom ash is mainly disposed of instead of being utilized. When landfilled, hazardous components, such as copper and zinc, can potentially be released to the environment and cause groundwater pollution. Therefore, extraction of copper and zinc would be a favorable solution for both disposal and utilization of bottom ash, as well as a potential source for secondary materials. In order to be economically feasible to recover metals from bottom ash, other metals and components probably need to be recovered as well. Acidic leaching solutions are most commonly used, however, alkaline solutions are generally more selective, less corrosive and have a lower reagent consumption according to previous studies. Ammonia-ammonium carbonate (AAC) is stated to be a suitable choice of leach solution for selective recovery of copper and zinc. The different substances of the AAC solution can be recovered, recombined and used in subsequent processing. In the present study, AAC leaching of bottom ash followed by a cementation procedure in order to selectively precipitate copper was investigated. Co-dissolution of zinc was also monitored during the study due to possible subsequent recovery based on procedures established in previous studies. MSWI bottom ash originating from different incineration plants in Norway was characterized and used in the study. The bottom ash was leached with an aqueous solution of ammonia (NH3) and ammonium carbonate ((NH4)2CO3). In order to efficiently extract copper from bottom ash, the AAC leaching procedure was optimized in terms of particle size, total ammonia concentration, leaching temperature, pulp density (solid/liquid ratio), and leaching time. The optimal leaching conditions were found to be 4.7 M, 60 C, 100 g bottom ash per liter leach solution and 180 minutes of leaching time, before the liquid and solid phases were separated. The pregnant leach solution (PLS) was quantitatively analyzed with inductively coupled plasma optical emission spectroscopy (ICP-OES). Extraction of more than 98 % of the copper from bottom ash was achieved. The copper was subsequently precipitated from the PLS by a cementation procedure with metallic zinc dust. After cementation, the PLS was quantitatively analyzed with ICP-OES and the solid residue was qualitatively analyzed using X-ray diffraction. More than 90% of copper was recovered from the PLS by cementation.
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Krengel, Ute & Montserrat Canals, Mateu
(2023).
Molecular warfare: A structural biology view on pathogen weapons — GbpA from Vibrio cholerae — and host defenses — Vg from the honey bee.
Universitetet i Oslo.
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Thiagarajan, Abilash Kanish; Brennhagen, Anders; Wragg, David Stephen & Koposov, Alexey
(2023).
Structural changes in graphite-based anodes of Li-ion batteries elucidated through operando XRD.
Kjemisk Institutt.
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Lithium-ion batteries (LIBs) with graphite-based anodes dominate the battery market around the world and have been studied extensively for the past decades, but the structural changes during cycling are still not fully understood. In this work, we used galvanostatic cycling (GC) to characterize the electrochemical performance of graphite samples in LIB. We also attempted to achieve stable capacities over hundreds of cycles to monitor the effect of long-term cycling on the mechanisms of graphite, with limited success. The fabricated coin cells experienced poor capacity retention across all graphite samples and some abnormal capacity increases that had not been observed previously. We noticed that electrolytes containing FEC made a noticeable change to the electrochemical performance as it resulted in irregular cycling, but also better capacity retention. Operando X-ray diffraction is a powerful technique to understand structural changes. We looked at multiple graphite reflections, mainly 002, 100, 101, 102 and 004, and observed that the expansion of the structure is not only 2 dimensions but all 3 dimensions as the interlayer distance and graphene layers expands during lithiation. We also monitored this expansion of graphene layers with pair distribution function (PDF) as the three C-C distances in hexagonal carbon rings, 1.41 Å, 2.41 Å and 2.85 Å, changed lengths at different points during lithiation and delithiation. We looked at diffraction peaks during lithiation and delithiation to study the mechanisms and observed that they were different. Lithiation showed solid solution like behavior indicating disordered intermediate phases, while delithiation showed two-phase transition indicating ordered structures. In this work we have used Operando X-ray diffraction to show that the structural changes graphite undergoes during cycling, transition from graphite to LiC6, is not specific to each graphite sample and the structural changes depend on the condition of the material. Pristine graphite samples transitioned fully to LiC6 during cycling with C-rate of C/6, but only LiC12 when a higher C-rate of C/2 was used. Graphite electrodes cut from commercial pouch cells that had cycled many hundreds of electrochemical cycles were able to transition to LiC6 during C/20, but only LiC12 during C/6, indicating an “ageing” mechanism.
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Kvalvik, Eva; Røberg-Larsen, Hanne & Wilson, Steven Ray Haakon
(2023).
Method Development for Detection of Underivatized Oxysterols in Cell Medium.
Kjemisk Institutt.
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Non-alcoholic fatty liver disease (NAFLD) is a disease caused by the accumulation of fat in the liver, mainly due to obesity and lifestyle. The disease is a worldwide health issue, with high prevalence and a lack of non-invasive biomarkers. To understand the disease, a model system is needed. The use of organoids, stem cell-derived three-dimensional cultures, is suggested as a model reflecting human physiology better than animal models. NAFLD can be induced in liver organoids. This enables the use of “Organ-in-a-Column” technology for studying the disease. Previous research has suggested that oxysterols are potential biomarkers of NAFLD. To make detection easier, oxysterols are usually derivatized in advance of analysis. “Organ-in-a-column” is an on-line system, in which organoids are coupled with Liquid Chromatography – Mass Spectrometry. The on-line approach makes sample preparation in the form of derivatization difficult. Therefore, this study has focused on method development for detecting underivatized oxysterols, with the aim of using the method in an “organ-in-a-column”-setup. Without a derivatization step in the sample preparation, the detection of oxysterols was challenging due to low sensitivity. Attempts of coeluting the groups of hydroxycholesterols and dihydroxycholesterols to establish a steatotic and control fingerprint from organoids with enhanced detection limit were partly successful for the analyte group of dihydroxycholesterols, but not the group of hydroxycholesterols. Sample clean-up was performed on-line using an automated filtration and filter flush solid phase extraction. This ensured robust analysis by the removal of particles before analysis. The optimized experimental parameters included a 5 𝜇L injection volume, a gradient elution utilizing isopropanol (IPA) as the organic modifier (20-65 %), 0.1 % formic acid for pH control in the mobile phase, and the use of a SuperPhenyl hexyl (2.1 mm x 5 cm) column at a temperature of 40 °C. The method allowed for detection of underivatized oxysterols in concentrations down to 0.050 𝜇g/mL in 10:90 IPA:Cell medium. The detection limit was too high to detect oxysterols secreted from liver organoids and the method needs further development before the organ-in-a-column approach can be used for disease monitoring. Also, adjustments to reduce the carry-over would be important to achieve a method providing reliable results.
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Hassan, Hoda Ali Kamil; Tveit, Svein & Fægri, Karoline
(2023).
Utvikling av et undervisningsopplegg med Vernier mini GC Plus i organisk syntese.
Kjemisk Institutt.
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Kromatografi er et tema der det er lett å bruke enkle og billige seperasjonsmetoder for å illustrere prinsippene for kromatografi. Samtidig skal kjemi, i lik linje med flere programfag på videregående skole, forberede elevene på videre studier og arbeidsliv ved å utvikle faglig og praktisk kompetanse. Målet med denne oppgaven er å utvikle et undervisningsopplegg som tar i bruk en minigasskromatograf, designet for bruk i skolen, for å analysere og vurdere renhet til produktet fra en organisk syntese. Forsøket som blir brukt i undervisningsopplegget har blitt videreutviklet for å være mer egnet til en 90 minutters laboratorie økt og undervisningsopplegget består av en prelab, en forsøksbeskrivelse og et etterarbeid. Resultatene viste blant annet at reaksjonstiden kunne bli redusert med ti minutter uten en signifikant effekt på produktet. Mange av oppgavene i prelaben og etterarbeidet hadde oppnådd hensikten de hadde i ulik grad, som førte til endringer på noen av de for å øke det potensielle utbytte. Oppgaver ble også lagt til på grunn av observasjoner gjort underveis i gjennomførelsen av undervisningsopplegget og teori, mens andre ble fjernet ved at hensikten ikke ble oppnådd eller at de var overflødige. Alle studentene var enige i at forsøksbeskrivelsen var lett å følge. Det reviderte undervisningsopplegget dekker tre kompetansemål fra læreplanen og flere kjerneelementer, og kan tilpasses hvis en minigasskromatograf ikke skulle være tilgjengelig.
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Solevåg, Silje & Wisthaler, Armin
(2023).
Emissions of volatile organic compounds from a closed landfill.
Kjemisk Institutt.
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The emission of volatile organic compounds (VOCs) from landfills is an environmental issue on both the global and local scale. In this study, the emissions of VOCs from Brånåsdalen nedlagte avfallsdeponi (Brånåsen closed landfill, BNA) were investigated by the use of on-site Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS) using a mobile laboratory. The study was divided into environmental and analytical chemistry aims. The environmental chemistry aim was to investigate which signals were detected in the mass spectra of landfill gas and determine which VOCs they could correspond to. 28 VOC signals assigned to five VOC compound classes (aliphatic hydrocarbons, oxygenated VOCs, sulfur VOCs, terpenes and aromatics) were detected and quantified in the landfill gas at BNA in this study. The VOC signals detected and their volume mixing ratios were found to have both temporal and spatial variation. This was attributed to the inhomogeneity of the disposed waste and the difference of the environmental conditions between sampling days. The signal of m/z 33.034, assigned to methanol, was found to be emitted in the highest volume mixing ratio, which corresponded to the results of a previous study. Landfill gas was also measured at a secondary landfill (Grønmo nedlagte avfallsdeponi, GNA) for comparison. The analytical chemistry aim was to compare the main sampling and measurement method of on-site PTR-ToF-MS using a mobile laboratory with two conventional sample collection methods; canister sampling followed by off-site PTR-ToF-MS and adsorption tube sampling followed by off-site gas chromatography-mass spectrometry (GC-MS). Canister sampling followed by off-site PTR-ToF-MS was found to replicate the results of on-site PTR-ToF-MS well. However, the main challenge was the instability of oxygenated VOCs during sample transport and storage and the possibility of sample contamination. Adsorption tube sampling followed by off-site gas GC-MS was found to yield similar volume mixing ratios as on-site PTR-ToF-MS for certain compounds. This method also allowed the identification of the signal of m/z 135.137 from on-site PTR-ToF-MS to β-pinene and 3-carene. Even so, a larger discrepancy was observed between the VOCs detected by adsorption tube sampling followed by off-site gas GC-MS and on-site PTR-ToF-MS. This was due to the formation of artifacts by the reaction of the adsorption material with ozone in ambient air and due to the respective detection limitations of the two analytical methods.
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Lindstad, Jostein; Tveit, Svein & Fægri, Karoline
(2023).
Utprøving og videreutvikling av undervisningsopplegg for identifisering av mikroplast i jord.
Kjemisk Institutt.
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Mikroplast utgjør et dagsaktuelt miljøproblem som ofte nevnes i media. I kjemi programfag er det å gi eksempler på produksjon, gjenvinning og nedbrytning av plast et nytt kompetansemål i læreplanen. Til nå finnes det få eller ingen laboratorieforsøk tilpasset norske videregående skoler hvor elevene får arbeidet med mikroplast. Derfor var målet med dette prosjektet å videreutvikle et forsøk for identifisering av mikroplast i jordprøver og tilpasse det slik at det kunne utføres i kjemi programfag. Et laboratorieforsøk utviklet for universitetsnivå ble videreutviklet og tilpasset forholdene i norsk videregående skole blant annet ved å redusere tidsbruken og ved å redusere mengden farlige kjemikalier og spesialutstyr som ble brukt. Det videreutviklede forsøket ble testet med jordprøver fra skogbunn, bekk, tursti, veikant, og ved fotballbaner. Vel bevandrede turstier og fotballbaner ble identifisert som godt egnede steder for å hente inn jordprøver som inneholdt mikroplast. Det videreutviklede forsøket ble prøvd ut i en pilotering med masterstudenter og av en klasse med kjemielever. Studien viste at elevene syns det å arbeide med blant annet vakuumfiltrering og å undersøke mikroplast med stereoluper var morsomt og spennende. Studien viste også at de fleste syns det var enkelt å forstå hva de skulle gjøre og hvordan i de ulike trinnene i laboratorieforsøket, og at trinnene var enkle å utføre i praksis. Det var noe større sprik i elevenes svar når det kom til å forestå hvorfor de ulike trinnene skulle utføres. Videre arbeid bør søke å undersøke måter å videre redusere tidsrammen rundt forsøket og å finne billigere alternativer til utstyr.
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