Search results for "Hydrogen"
showing 10 items of 4254 documents
Electrochemical sensor for evaluating oxidative stress in airway epithelial cells
2021
Cigarette smoke exposure induces oxidative stress within the airways. Increased oxidative burden contributes to the pathogenesis of chronic lung disorders and is associated with aging and chronic inflammation. Airway epithelial cells highly contribute to Reactive Oxygen Species (ROS) generation within injured and inflamed lung tissues. Among ROS, hydrogen peroxide (H2O2) can be monitored in the extracellular space. Herein, we present an amperometric/voltammetric sensor based on gold nanoparticles and graphene oxide able to detect H2O2 with good sensitivity and selectivity. Using this sensor, H2O2 release was measured in conditioned medium from primary bronchial epithelial cells (PBEC), bron…
N-[Glycyl-(Z)-α,β-dehydrophenylalanylglycyl-(Z)-α,β-dehydrophenylalanyl]glycine trifluoroacetate methanol solvate
2007
The molecular conformation of the title dehydropeptide, H+-Gly1–ΔZPhe2–Gly3–ΔZPhe4–Gly5-OH·CF3COO−·CH3OH or C24H26N5O6+·CF3COO−·CH3OH, is characterized by the presence of two intramolecular N—H⋯O hydrogen bonds that stabilize two type III β-turns, at the ΔZPhe2 (ΔZPhe is the Z isomer of the α,β-dehydrophenylalanine residue) and Gly3, and Gly3 and ΔZPhe4 residues. As a result, the pentapeptide adopts a right-handed 310-helical conformation. All peptide units are linked trans to each other.
N‐[tert‐Butoxycarbonylglycyl‐(E)‐α,β‐dehydrophenylalanylglycylglycyl‐(E)‐α,β‐dehydrophenylalanyl]glycine
2006
In the molecule of the title hexapeptide, Boc0–Gly1–ΔEPhe2–Gly3–Gly4–ΔEPhe5–Gly6–OH, C31H36N6O9, there are two overlapping β-turns, one of type II on the ΔEPhe2 (ΔEPhe is isomer E of the α,β-dehydrophenylalanine residue) and Gly3 residues and the second of type III′ on the Gly3 and Gly4 residues. All amino acids in the peptide are linked trans to each other. Three relatively strong intramolecular N—H⋯O hydrogen bonds stabilize the crystal structure. Two of them, of the 4→1 type, are responsible for two β-turns in the peptide.
Conformational investigation of α, β-dehydropeptides
2009
The crystal structure of Ac-Pro-delta Val-NHCH3 was examined to determine the influence of the alpha,beta-dehydrovaline residue on the nature of peptide conformation. The peptide crystallizes from methanol-diethyl ether solution at 4 degrees in needle-shaped form in orthorhombic space group P2(1)2(1)2(1) with a = 11.384(2) A, b = 13.277(2) A, c = 9.942(1) A, V = 1502.7(4) A3, Z = 4, Dm = 1.17 g.cm-3 and Dc = 1.18 g.cm-3. The structure was solved by direct methods using SHELXS-86 and refined to an R value of 0.057 for 1922 observed reflections. The peptide is found to adopt a beta-bend between the type I and the type III conformation with phi 1 = -68.3(4) degrees, psi 1 = -20.1(4) degrees, p…
Nucleoside phosphotransferase of chick embryo
1979
This paper describes a purification procedure and some properties of a nonspecific nucleoside phosphotransferase of chick embryo, an activity which catalyzes the transfer of chick embryo, an activity which catalyzes the transfer of the phosphate ester from a deoxyribonucleotide or a pyrimidine ribonucleotide to a deoxyribonucleoside acceptor. The enzyme is very unstable to heat, dilution and dialysis and it is almost entirely inactivated by DEAE-cellulose chromatography or gel filtration. A marked enhancement in its stability is caused by numerous nucleotides. In these experiments at least 920-fold purification was obtained by using dTTP (50 microM) as nucleotide protector. The enzyme, puri…
2,5-Dialkoxysubstituierte Oligo- und Poly(1,4-phenylenethenylen)e
1994
2,5-Dialkoxy Substituted Oligo- and Poly(1,4-phenyleneethenylene)s O-Alkylation and regioselective Rieche formylation of 2-methylhydroquinone (1) yields the 2,5-dialkoxy-4-methylbenzaldehydes 4a–j. The corresponding azomethines 5a–j enter in a strongly alkaline medium a selfcondensation reaction leading to the title compounds 6/7a–j. These conjugated oligomers and polymers possess highly regular structures with exclusively (E)-configurated double bonds. GPC, IR, 1H-, 13C-NMR and MS-FD measurements were used for their characterization. Somewhat different results were obtained for the similarly prepared Schiff base 5l which contains chlorine substituents in the side chains. Cleavage of hydrog…
Preparation of extracts from mature spruce needles for enzymatic analyses
1987
It was possible to extract simultaneously several active enzymes involved in the carbohydrate or the amino acid metabolism from spruce needles [Picea abies (L.) Karst.] when a) a 100 mM Na-Pi buffer of pH 7.5 containing 5% PVPP and 0.5% Triton X-100 was used and when b) the resulting crude extracts were freed from lowmolecular-weight compounds by gel-chromatography using the separation medium Fractogel TSK HW-40. Besides Triton X-100, Triton X-305, Myrij-52 and Brij-35 were tested, but 0.5% Triton X-100 brought about the most active enzyme extracts. In crude extracts prepared from spruce needles during the early summer a high increase in absorbance at 334 nm was observed when the co-substra…
Cu2+ Coordination Properties of a 2-Pyridine Heptaamine Tripod: Characterization and Binding Mechanism
2009
The synthesis, protonation, and Cu(2+) coordination chemistry of a tripodal heptaamine ligand (L(1)) functionalized with 2-pyridine fragments at the ends of its three branches are reported. L(1) presents six relatively high protonation constants followed by much more reduced constant that as indicated by the UV-vis and NMR data, occur on the pyridine fragments. p[H]-metric, ESI/MS(+), EPR and UV-vis data show that L(1) is able to form mono-, di-, and trinuclear Cu(2+) complexes. Slippage movements and molecular reorganizations have been observed to occur as a function of p[H] in the 1:1 Cu(2+) complexes. The kinetic studies showed that the complex formation is fast and proceeds through a di…
Studien zum Vorgang der Wasserstoffübertragung, 53. Beitrag zur Kenntnis der elektroreduktiven Spaltung von Hydroxylaminderivaten
1978
Die Elektroreduktion von 26 Hydroxylaminderivaten wird polarographisch und an 6 Beispielen praparativ untersucht. Es wurde gefunden: 1) Dreifach mit Alkyl- oder Arylgruppen substituierte Hydroxylaminderivate werden bis zu einem Potential von -2.5 V (gegen Ag/AgCl/KClges.) nicht elektroreduziert. — 2) Der Einbau von Acylgruppen erleichtert in Abhangigkeit von Art, Zahl und Verknupfungsstelle die Elektroreduktion. Acylreste mit aromatischen Gruppen verschieben das Halbstufenpotential starker nach positiven Werten als aliphatisch substituierte Acylreste (entsprechend: Phthaloyl > Benzoyl > Formyl > Acetyl > Ethoxycarbonyl). Acylgruppen am Sauerstoff des Hydroxylamins fordern die Elektroredukti…
B-DNA Structure and Stability as Function of Nucleic Acid Composition. Dispersion-Corrected DFT Study of Dinucleoside-Monophosphate Single and Double…
2013
actions of the sugar-phosphate skeleton with water; (6) hydrophobic interactions of the DNA cylindrical core, made up by the hydrogen-bonded and stacked nitrogen bases, with the water solvent. Recently, there has been increasing effort in developing and applying quantum chemical methods able to reproduce the structure of native B-DNA and to correctly describe the energy involved in the intrastrand and interstrand noncovalent interactions between the nucleotide monomers. This topic has been approached by both wave function methods and density functional theory. [2] Water solvent and sodium counterions also play an important role in the formation and relative stabilization of the double-helic…