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121.
Nicolis S Pennati A Perani E Monzani E Sanangelantoni AM Casella L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(3):749-757
The modification of human myoglobin (HMb) by reaction with nitrite and hydrogen peroxide has been investigated. This reaction is important because NO(2) (-) and H(2)O(2) are formed in vivo under conditions of oxidative and nitrative stress, where protein derivatization has been often observed. The abundance of HMb in tissues and in the heart makes it a potential source and target of reactive species generated in the body. The oxidant and nitrating species produced by HMb/H(2)O(2)/NO(2) (-) are nitrogen dioxide and peroxynitrite, which can react with exogenous substrates and endogenous protein residues. Tandem mass analysis of HMb modified by stoichiometric amounts of H(2)O(2) and NO(2) (-) indicated the presence of two endogenous derivatizations: oxidation of C110 to sulfinic acid (76 %) and nitration of Y103 to 3-nitrotyrosine (44 %). When higher concentrations of NO(2) (-) and H(2)O(2) were used, nitration of Y146 and of the heme were also observed. The two-dimensional gel-electrophoretic analysis of the modified HMbs showed spots more acidic than that of wild-type HMb, a result in agreement with the formation of sulfinic acid and nitrotyrosine residues. By contrast, the reaction showed no evidence for the formation of protein homodimers, as observed in the reaction of HMb with H(2)O(2) alone. Both HMb and the modified HMb are active in the H(2)O(2)/NO(2) (-)-dependent nitration of exogenous phenols. Their catalytic activity is quite similar and the endogenous modifications of HMb therefore have little effect on the reactivity of the protein intermediates. 相似文献
122.
Sergio Albeverio Francesco C. De Vecchi Stefania Ugolini 《Journal of statistical physics》2017,168(3):483-507
We prove the entropy-chaos property for the system of N indistinguishable interacting diffusions rigorously associated with the ground state of N trapped Bose particles in the Gross–Pitaevskii scaling limit of infinitely many particles. On the path-space we show that the sequence of probability measures of the one-particle interacting diffusion weakly converges to a limit probability measure, uniquely associated with the minimizer of the Gross-Pitaevskii functional. 相似文献
123.
Gärtner F Denurra S Losse S Neubauer A Boddien A Gopinathan A Spannenberg A Junge H Lochbrunner S Blug M Hoch S Busse J Gladiali S Beller M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(11):3220-3225
Novel phenylazole ligands were applied successfully in the synthesis of cyclometalated iridium(III) complexes of the general formula [Ir(phenylazole)(2)(bpy)]PF(6) (bpy=2,2'-bipyridine). All complexes were fully characterized by NMR, IR, and MS spectroscopic studies as well as by cyclic voltammetry. Three crystal structures obtained by X-ray analysis complemented the spectroscopic investigations. The excited-state lifetimes of the iridium complexes were determined and showed to be in the range of several hundred ns to multiple μs. All obtained iridium complexes were active as photosensitizers in catalytic hydrogen evolution from water in the presence of triethylamine as a sacrificial reducing agent. Applying an in situ formed iron-based water reduction catalyst derived from [HNEt(3)](+) [HFe(3)(CO)(11)](-) and tris[3,5-tris-(trifluoromethyl)-phenyl]phosphine as the ligand, [Ir(2-phenylbenz-oxazole)(2)-(bpy)]PF(6) proved to be the most efficient complex giving a quantum yield of 16% at 440 nm light irradiation. 相似文献
124.
Nostro A Filocamo A Giovannini A Catania S Costa C Marino A Bisignano G 《Natural product research》2012,26(22):2132-2136
This study reported the antimicrobial activity and phenolic content of natural site and micropropagated Limonium avei (De Not.) Brullo & Erben inflorescences. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ethanolic extracts were determined according to the Clinical Laboratory Standards Institute guidelines. Individual phenolic acids and flavonoids were detected by a high performance liquid chromatography (HPLC-DAD) method. The samples showed a comparable antimicrobial activity, although the natural site extract possessed the lower MIC values. The best activity was detected against Gram-positive bacteria, such as Staphylococcus aureus including methicillin resistant strains (MIC and MBC values ranging from 7.81 to 62.50?μg?mL(-1) and from 500 to 2000?μg?mL(-1) respectively). In contrast, a low activity was found on Gram-negative bacteria and Candida albicans. The HPLC-DAD analysis revealed ten phenolic acids and four flavonoids with a major amount of m-coumaric acid, naringin and quercetin in the natural site extract. 相似文献
125.
A chemoselective, mild, and versatile method for performing postsynthetic modifications of peptide sequences is described. It requires only activated molecular sieves in the presence of an alkyl halide in order to N-alkylate lysine side chains. This reaction is fully compatible with most of the peptide functionalities, discriminates the reactivity of differently protected lysines, and proceeds in good yield. The mild conditions employed were further proved by performing the N-alkylation of a peptide containing a disulfide bridge. 相似文献
126.
Cuoghi A Caiazzo M Bellei E Monari E Bergamini S Palladino G Ozben T Tomasi A 《Analytical and bioanalytical chemistry》2012,404(6-7):2097-2104
Chronic renal failure patients accumulate in the blood molecules that are normally excreted into the urine. p-Cresol Sulphate (pCS), the most representative retained toxin, shows a high level of toxicity. Therefore, its quantification could represent a prediction factor to determine the risk of endothelial dysfunction and cardiovascular complication and response to the haemodialysis treatment. The aim of this study was to evaluate the suitability of the multiple reaction monitoring (MRM) technique in order to improve the sensibility, the selectivity and the timing of pCS detection in a small amount of plasma. Deproteinized plasma of uremic patients was concentrated and dissolved in liquid chromatography (LC) mobile phase solution. pCS was quantified by LC coupled to tandem mass spectrometry (LC-MS/MS) on a triple-quadrupole mass spectrometer. Selective and sensitive detection of pCS was achieved by selecting the specific parent ion and monitoring two specific fragment ions. The MRM assay was carried out using the following transitions: m/z 187?→?80.00 and m/z 187?→?107.00. A good linearity was observed for each calibration curve. The intra-day and inter-day results showed a good precision and repeatability. The percentage recoveries indicate an optimal selectivity of the analytical method. The MRM assay to quantify pCS in a small amount of human plasma is rapid, highly sensitive, selective and with a good repeatability. 相似文献
127.
Di Bella S Oliveri IP Colombo A Dragonetti C Righetto S Roberto D 《Dalton transactions (Cambridge, England : 2003)》2012,41(23):7013-7016
A luminescent bis(salicylaldiminato)zinc(II) Schiff-base complex, 1, is characterized by a concentration dependent second-order nonlinear optical response, related to the degree of aggregation of the complex in a dichloromethane solution. The formation of the monomeric adduct, by addition of a Lewis base, such as pyridine, to concentrated solutions of 1, leads to a switch-on of the quadratic hyperpolarizability. This represents an unprecedented mode of NLO switching in molecular materials. 相似文献
128.
M Viciano-Chumillas M Giménez-Marqués S Tanase I Mutikainen U Turpeinen JM Smits R de Gelder L Jos de Jongh J Reedijk 《Dalton transactions (Cambridge, England : 2003)》2012,41(34):10249-10257
New manganese compounds [Mn(HphpzMe)(2)(H(2)phpzMe)(HCO(2))] (1), [Mn(2)(phpzMe)(2)(HphpzMe)(2)(OCH(3))]·2CH(3)OH (2), Na{[Mn(HphpzPh)(phpzPh)(MeOH)(2)](2)}(HCO(2)) (3), [Mn(HphpzPh)(2)(EtOH)(2)]ClO(4)·2EtOH (4) and [Mn(HphpzPh)(2)N(3)] (5) were synthesized and characterized with various techniques. 1, 4 and 5 are mononuclear manganese(iii) compounds, 2 is a mixed-valence dinuclear manganese(iii/iv) compound, and 3 is a trinuclear compound containing two manganese(iii) ions and a sodium(i) ion. A remarkable feature is the spontaneous formation of the formate ion as a result of the methanol or methoxide oxidation in compounds 1 and 3. Using ethanol precludes the formation of the formate and compound 4 is obtained. The molecular structure of all compounds is stabilized by supramolecular interactions, including strong hydrogen bonding and π-π interactions. 相似文献
129.
Stefania Bellavia Maria Macconi Sandra Pieraccini 《Computational Optimization and Applications》2012,53(3):771-794
We focus on the numerical solution of medium scale bound-constrained systems of nonlinear equations. In this context, we consider an affine-scaling trust region approach that allows a great flexibility in choosing the scaling matrix used to handle the bounds. The method is based on a dogleg procedure tailored for constrained problems and so, it is named Constrained Dogleg method. It generates only strictly feasible iterates. Global and locally fast convergence is ensured under standard assumptions. The method has been implemented in the Matlab solver CoDoSol that supports several diagonal scalings in both spherical and elliptical trust region frameworks. We give a brief account of CoDoSol and report on the computational experience performed on a number of representative test problems. 相似文献
130.
Dr. Julien Briand Dr. Stefania Fusi Dr. Riccardo Rossi Paccani Prof. Massimo Olivucci Prof. Stefan Haacke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15296-15304
The coherent photoisomerization of a chromophore in condensed phase is a rare process in which light energy is funneled into specific molecular vibrations during electronic relaxation from the excited to the ground state. In this work, we employed ultrafast spectroscopy and computational methods to investigate the molecular origin of the coherent motion accompanying the photoisomerization of indanylidene–pyrroline (IP) molecular switches. UV/Vis femtosecond transient absorption gave evidence for an excited‐ and ground‐state vibrational wave packet, which appears as a general feature of the IP compounds investigated. In close resemblance to the coherent photoisomerization of rhodopsin, the sudden onset of a far‐red‐detuned and rapidly blue‐shifting photoproduct signature indicated that the population arriving on the electronic ground state after nonadiabatic decay through the conical intersection (CI) is still very focused in the form of a vibrational wave packet. Semiclassical trajectories were employed to investigate the reaction mechanism. Their analysis showed that coupled double‐bond twisting and ring inversions, already populated during the excited‐state reactive motion, induced periodic changes in π‐conjugation that modulate the ground‐state absorption after the non‐adiabatic decay. This prediction further supports that the observed ground‐state oscillation results from the reactive motion, which is in line with a biomimetic, coherent photoisomerization scenario. The IP compounds thus appear as a model system to investigate the mechanism of mode‐selective photomechanical energy transduction. The presented mechanism opens new perspectives for energy transduction at the molecular level, with applications to the design of efficient molecular devices. 相似文献