Publications by authors named "Klose D"

Background: Individuals with maturity-onset diabetes of the young (MODY) are often misdiagnosed as type 1 or type 2 diabetes and receive inappropriate care. We aimed to investigate the characteristics and treatment of all MODY types in a multicenter, real-world setting.

Methods: Individuals with MODY from the diabetes prospective follow-up (DPV) registry were studied.

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The CH oxidation performance of Cu-chabazite zeolites characterized by distinct Si/Al ratios and Cu loadings has been studied and the observed variations in reactivity have been correlated to the differences in the nature of the formed active centers. Plug flow reactor tests, in situ Fourier-transform infrared, and X-ray absorption spectroscopy demonstrate that a decrease in Cu loading shifts the reactivity/redox profile to higher temperatures and increases the CHOH selectivity and Cu-efficiency. In situ electron paramagnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared, and photoluminescence spectroscopies reveal that this behavior is associated with the presence of monomeric Cu active sites, including bare Cu and [CuOH] present at low Si/Al ratio and Cu loading.

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Hybrid methylammonium (MA) lead halide perovskites have emerged as materials exhibiting excellent photovoltaic performance related to their rich structural and dynamic properties. Here, we use multifrequency (X-, Q-, and W-band) electron paramagnetic resonance (EPR) spectroscopy of Mn impurities in MAPbCl to probe the structural and dynamic properties of both the organic and inorganic sublattices of this compound. The temperature dependent continuous-wave (CW) EPR experiments reveal a sudden change of the Mn spin Hamiltonian parameters at the phase transition to the ordered orthorhombic phase indicating its first-order character and significant slowing down of the MA cation reorientation.

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Characterization of paramagnetic compounds, in particular regarding the detailed conformation and electronic structure, remains a challenge, and - still today it often relies solely on the use of X-ray crystallography, thus limiting the access to electronic structure information. This is particularly true for lanthanide elements that are often associated with peculiar structural and electronic features in relation to their partially filled f-shell. Here, we develop a methodology based on the combined use of state-of-the-art magnetic resonance spectroscopies (EPR and solid-state NMR) and computational approaches as well as magnetic susceptibility measurements to determine the electronic structure and geometry of a paramagnetic Yb(III) alkyl complex, Yb(III)[CH(SiMe)], a prototypical example, which contains notable structural features according to X-ray crystallography.

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To characterize structure and molecular order in the nanometre range, distances between electron spins and their distributions can be measured via dipolar spin-spin interactions by different pulsed electron paramagnetic resonance experiments. Here, for the single-frequency technique for refocusing dipolar couplings (SIFTER), the buildup of dipolar modulation signal and intermolecular contributions is analysed for a uniform random distribution of monoradicals and biradicals in frozen glassy solvent by using the product operator formalism for electron spin . A dipolar oscillation artefact appearing at both ends of the SIFTER time trace is predicted, which originates from the weak coherence transfer between biradicals.

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The ethylene polymerization Phillips catalyst has been employed for decades and is central to the polymer industry. While Cr(III) alkyl species are proposed to be the propagating sites, there is so far no direct experimental evidence for such proposal. In this work, by coupling Surface organometallic chemistry, EPR spectroscopy, and machine learning-supported XAS studies, we have studied the electronic structure of well-defined silica-supported Cr(III) alkyls and identified the presence of several surface species in high and low-spin states, associated with different coordination environments.

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Background: A compelling body of evidence implicates cigarette smoking and lung inflammation in Multiple Sclerosis (MS) susceptibility and progression. Previous studies have reported epigenetic age (DNAm age) acceleration in blood immune cells and in glial cells of people with MS (pwMS) compared to healthy controls (HC).

Objectives: We aimed to examine biological ageing in lung immune cells in the context of MS and smoking.

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Propane dehydrogenation is an important industrial reaction to access propene, the world's second most used polymer precursor. Catalysts for this transformation are required to be long living at high temperature and robust toward harsh oxidative regeneration conditions. In this work, combining surface organometallic chemistry and thermolytic molecular precursor approach, we prepared well-defined silica-supported Pt and alloyed PtZn materials to investigate the effect of Ti-doping on catalytic performances.

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Cu-exchanged mordenite (MOR) is a promising material for partial CH oxidation. The structural diversity of Cu species within MOR makes it difficult to identify the active Cu sites and to determine their redox and kinetic properties. In this study, the Cu speciation in Cu-MOR materials with different Cu loadings has been determined using operando electron paramagnetic resonance (EPR) and operando ultraviolet-visible (UV/Vis) spectroscopy as well as in situ photoluminescence (PL) and Fourier-transform infrared (FTIR) spectroscopy.

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Article Synopsis
  • The study examined pediatric type 2 diabetes (T2D) incidence in Germany during the COVID-19 pandemic (2020-2021) compared to the years 2011-2019.
  • The findings revealed a significant rise in youth-onset T2D incidence in 2021, particularly affecting adolescent boys, despite no notable increase for girls.
  • The results suggest a concerning trend in T2D prevalence among children, with a shift in the sex ratio for T2D incidence towards boys during the pandemic.
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Article Synopsis
  • The study investigates the low-temperature Hahn echo decay signal of a specific nitroxide, revealing two distinct contributions due to the tunneling of methyl groups and matrix-induced decoherence.
  • A new model called the methyl quantum rotor (MQR) is introduced to explain how multiple methyl rotors affect the electron spin, allowing for the characterization of the methyl groups' rotation barrier distribution in a glassy matrix.
  • The findings align well with density functional theory calculations, confirming the significance of methyl tunneling in the spin system and its independence from magnetic and temperature variations between 10 and 50 K.
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At low temperature, methyl groups act as hindered quantum rotors exhibiting rotational quantum tunneling, which is highly sensitive to a local methyl group environment. Recently, we observed this effect using pulsed electron paramagnetic resonance (EPR) in two dimethylammonium-containing hybrid perovskites doped with paramagnetic Mn ions. Here, we investigate the feasibility of using an alternative fast-relaxing Co paramagnetic center to study the methyl group tunneling, and, as a model compound, we use dimethylammonium zinc formate [(CH)NH][Zn(HCOO)] hybrid perovskite.

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Imaging of iron-based nanoparticles (NPs) remains challenging because of the presence of endogenous iron in tissues that is difficult to distinguish from exogenous iron originating from the NPs. Here, an analytical cascade for characterizing the biodistribution of biomedically relevant iron-based NPs from the organ scale to the cellular and subcellular scales is introduced. The biodistribution on an organ level is assessed by elemental analysis and quantification of magnetic iron by electron paramagnetic resonance, which allowed differentiation of exogenous and endogenous iron.

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The Union Carbide (UC) ethylene polymerization catalysts, based on chromocene dispersed on silica, show distinct features from the Phillips catalysts, but share the same heated debate regarding the structure of their active sites. Based on a combination of IR, EPR spectroscopies, labeling experiments, and DFT modeling, we identified monomeric surface-supported Cr(iii) hydrides, ([triple bond, length as m-dash]SiO)Cr(Cp)-H, as the active sites of the UC catalyst. These sites are formed in the presence of grafted and adsorbed chromocene as well as residual surface OH groups, only possible at high Cr loading, and involve a C-H activation of the Cp ring.

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Background: Multiple sclerosis (MS) is a chronic inflammatory neurodegenerative disease of the central nervous system (CNS) characterized by irreversible disability at later progressive stages. A growing body of evidence suggests that disease progression depends on age and inflammation within the CNS. We aimed to investigate epigenetic aging in bulk brain tissue and sorted nuclei from MS patients using DNA methylation-based epigenetic clocks.

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Synthetic iron-sulfur cubanes are models for biological cofactors, which are essential to delineate oxidation states in the more complex enzymatic systems. However, a complete series of [FeS] complexes spanning all redox states accessible by 1-electron transformations of the individual iron atoms ( = 0-4+) has never been prepared, deterring the methodical comparison of structure and spectroscopic signature. Here, we demonstrate that the use of a bulky arylthiolate ligand promoting the encapsulation of alkali-metal cations in the vicinity of the cubane enables the synthesis of such a series.

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The increasing demand for short chain olefins like propene for plastics production and the availability of shale gas make the development of highly performing propane dehydrogenation (PDH) catalysts, robust toward industrially applied harsh regeneration conditions, a highly important field of research. A combination of surface organometallic chemistry and thermolytic molecular precursor approach was used to prepare a nanometric, bimetallic Pt-Mn material (3 wt % Pt, 1.3 wt % Mn) supported on silica consecutive grafting of a Mn and Pt precursor on surface OH groups present on the support surface, followed by a treatment under a H flow at high temperature.

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Reaction of the 6π-electron aromatic four-membered heterocycle (IPr) C P (1) (IPr=1,3-bis(2,6-diisopropylphenyl)-1,3-dihydro-2H-imidazol-2-ylidene) with [Fe CO ] gives the neutral iron tricarbonyl complex [Fe(CO) -η -{(IPr) C P }] (2). Oxidation with two equivalents of the ferrocenium salt, [Fe(Cp) ](BArF ), affords the dicationic tricarbonyl complex [Fe(CO) -η -{(IPr) C P }](BArF ) (4). The one-electron oxidation proceeds under concomitant loss of one CO ligand to give the paramagnetic dicarbonyl radical cation complex [Fe(CO) -η -{(IPr) C P }](BArF ) (5).

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In a wide spectrum of neurodegenerative diseases, self-assembly of pathogenic proteins to cytotoxic intermediates is accelerated by the presence of metal ions such as Cu. Only low concentrations of these early transient oligomeric intermediates are present in a mixture of species during fibril formation, and hence information on the extent of structuring of these oligomers is still largely unknown. Here, we investigate dimers as the first intermediates in the Cu-driven aggregation of a cyclic D,L-α-peptide architecture.

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Objective: The aim of this study was to investigate the incidence of type 1 diabetes in children and adolescents during the coronavirus disease 2019 (COVID-19) pandemic in Germany compared with previous years.

Research Design And Methods: Based on data from the multicenter German Diabetes Prospective Follow-up Registry, we analyzed the incidence of type 1 diabetes per 100,000 patient-years in children and adolescents from 1 January 2020 through 30 June 2021. Using Poisson regression models, expected incidences for 2020/21 were estimated based on the data from 2011 to 2019 and compared with observed incidences in 2020/21 by estimating incidence rate ratios (IRRs) with 95% CIs.

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Förster resonance energy transfer (FRET) and electron paramagnetic resonance (EPR) spectroscopy are complementary techniques for quantifying distances in the nanometer range. Both approaches are commonly employed for probing the conformations and conformational changes of biological macromolecules based on site-directed fluorescent or paramagnetic labeling. FRET can be applied in solution at ambient temperature and thus provides direct access to dynamics, especially if used at the single-molecule level, whereas EPR requires immobilization or work at cryogenic temperatures but provides data that can be more reliably used to extract distance distributions.

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The ATP hydrolysis transition state of motor proteins is a weakly populated protein state that can be stabilized and investigated by replacing ATP with chemical mimics. We present atomic-level structural and dynamic insights on a state created by ADP aluminum fluoride binding to the bacterial DnaB helicase from Helicobacter pylori. We determined the positioning of the metal ion cofactor within the active site using electron paramagnetic resonance, and identified the protein protons coordinating to the phosphate groups of ADP and DNA using proton-detected P,H solid-state nuclear magnetic resonance spectroscopy at fast magic-angle spinning > 100 kHz, as well as temperature-dependent proton chemical-shift values to prove their engagements in hydrogen bonds.

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Article Synopsis
  • Despite extensive research, the atomic-scale structure of active sites in Ziegler-Natta catalysts, crucial for the chemical industry, remains unclear.
  • This study reveals the structure of dormant active sites using magnetic resonance techniques, specifically EPR and NMR, and correlates them with polymerization activity.
  • The findings suggest an ethylene polymerization mechanism involving bimetallic alkyl-Ti(III),Al species, linking spectroscopic data to the active species formed during ethylene presence through DFT calculations.
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While Ti(iii) alkyl species are the proposed active sites in Ziegler-Natta ethylene polymerization catalysts, the corresponding well-defined homogeneous catalysts are not known. We report that well-defined neutral β-diiminato Ti(iii) alkyl species, namely [Ti(nacnac)(CH Bu)] and its alumina-grafted derivative [(AlO)Ti(nacnac)(CH Bu)], are active towards ethylene polymerization at moderate pressures and temperatures and possess an electron configuration well-adapted to insertion of ethylene. Advanced EPR spectroscopy showed that ethylene insertion into a Ti(iii)-C bond takes place during polymerization from Ti(nacnac)(CH Bu).

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Article Synopsis
  • The study focuses on the selective conversion of methane to methanol using copper-exchanged zeolites, presenting a promising approach in chemistry.
  • Various active sites, especially well-dispersed monomeric Cu species supported on alumina, are explored for their reactivity in this two-electron process.
  • Spectroscopic techniques like electron paramagnetic resonance (EPR) reveal that the effective active sites correspond to specific alumina facets, enabling the effective transformation of methane to methanol.
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