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Publisher: Melville, NY : American Inst. of Physics × Subject: Atoms ×

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Now showing 1 - 2 of 2
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    Reactive species driven oxidative modifications of peptides—Tracing physical plasma liquid chemistry
    (Melville, NY : American Inst. of Physics, 2021) Wenske, Sebastian; Lackmann, Jan-Wilm; Busch, Larissa Milena; Bekeschus, Sander; von Woedtke, Thomas; Wende, Kristian
    The effluence of physical plasma consists of a significant share of reactive species, which may interact with biomolecules and yield chemical modifications comparable to those of physiological processes, e.g., post-translational protein modifications (oxPTMs). Consequentially, the aim of this work is to understand the role of physical plasma-derived reactive species in the introduction of oxPTM-like modifications in proteins. An artificial peptide library consisting of ten peptides was screened against the impact of two plasma sources, the argon-driven MHz-jet kINPen and the helium-driven RF-jet COST-Jet. Changes in the peptide molecular structure were analyzed by liquid chromatography–mass spectrometry. The amino acids cysteine, methionine, tyrosine, and tryptophan were identified as major targets. The introduction of one, two, or three oxygen atoms was the most common modification observed. Distinct modification patterns were observed for nitration (+N + 2O–H), which occurred in kINPen only (peroxynitrite), and chlorination (+Cl–H) that was exclusive for the COST-Jet in the presence of chloride ions (atomic oxygen/hypochlorite). Predominantly for the kINPen, singlet oxygen-related modifications, e.g., cleavage of tryptophan, were observed. Oxidation, carbonylation, and double oxidations were attributed to the impact of hydroxyl radicals and atomic oxygen. Leading to a significant change in the peptide side chain, most of these oxPTM-like modifications affect the secondary structure of amino acid chains, and amino acid polarity/functionality, ultimately modifying the performance and stability of cellular proteins.
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    Design of the electronic structure and properties of calcium apatites via isomorphic modification of the cation sublattice, and prospects of their application
    (Melville, NY : American Inst. of Physics, 2024) Karbivskyy, V.; Kurgan, N.; Hantusch, M.; Romansky, A.; Sukhenko, I.; Karbivska, L.
    The evolution of the valence band, charge states of atoms, and optical and vibrational spectra in compounds Ca10−xMx(PO4)xY2, M = Fe, Ni, Cu, Mg; Y = OH, Cl, F was studied by using XPS, infrared, and optical spectroscopy, with the addition of quantum mechanics calculations. The changes in the bandgap in these compounds were analyzed. Isomorphic substitution of calcium ions in the cationic sublattice of calcium hydroxyapatite by metal ions changes the shape of the curve that represents the occupied part of the valence band only slightly. It retains a pronounced gapped character with different lengths of individual subbands—the upper and lower parts of the valence band. It is shown that the predominant position of rare earth and uranium atoms in the apatite structure is the Ca(2)-position. Isomorphic substitution of calcium atoms by metal atoms (Fe, Ni, Cu, Mg) in the apatite structure in the range of 1%-2% of atoms leads to the narrowing of the energy gap. The most significant narrowing is observed when calcium is substituted by nickel and copper. The theoretically calculated bandgap width in calcium apatites can be well described in terms of the generalized gradient approximation. The design of the structure of calcium apatites via the method of isomorphic substitutions in the cation sublattice makes it possible to control the bandgap width, thus expanding the field of practical application of these compounds.