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排序方式: 共有394条查询结果,搜索用时 15 毫秒
1.
Fabbrizzi L Foti F Licchelli M Maccarini PM Sacchi D Zema M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(21):4965-4972
A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of trigonal bipyramidal stereochemistry, as shown by X-ray diffraction studies performed on the crystalline complex salt. At pH 7.5, an OH- ion binds the metal and a six-coordinate species forms. The binding-detachment of the pendant arm to/from the NiII center is signaled by changes in the emission properties of the dansyl subunit in the side chain; the fluorescence of this side chain is high when the pendant arm is not coordinated and low when the sulfonamide group is bound to the metal. The system investigated represents the prototype of a light-emitting molecular machine, driven by a pH change. 相似文献
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Sottini S Abbruzzetti S Spyrakis F Bettati S Ronda L Mozzarelli A Viappiani C 《Journal of the American Chemical Society》2005,127(49):17427-17432
Biphasic geminate rebinding of CO to myoglobin upon flash photolysis has been associated to ligand distribution in hydrophobic cavities, structurally detected by time-resolved crystallography, xenon occupancy, and molecular simulations. We show that the time course of CO rebinding to human hemoglobin also exhibits a biphasic geminate rebinding when the protein is entrapped in wet nanoporous silica gel. A simple branched kinetic scheme, involving the bound state A, the primary docking site C, and a secondary binding site B was used to calculate the microscopic rates and the time-dependent population of the intermediate species. The activation enthalpies of the associated transitions were determined in the absence and presence of 80% glycerol. Potential hydrophobic docking cavities within the alpha and beta chains of hemoglobin were identified by computational modeling using xenon as a probe. A hydrophobic pocket on the distal side of the heme, corresponding to Xe4 in Mb, and a nearby site that does not have a correspondence in Mb were detected. Neither potential xenon sites on the proximal side nor a migration channel from the distal to proximal site was located. The small enthalpic barriers between states B and C are in very good agreement with the location of the xenon sites on the distal side. Furthermore, the connection between the two xenon sites is relatively open, explaining why the decreased mobility of the protein with viscosity only slightly perturbs the energetics of ligand migration between the two sites. 相似文献
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Juciane Prois Fortes Fernanda Wouters Franco Julia Baranzelli Gustavo Andrade Ugalde Cristiano Augusto Ballus Eliseu Rodrigues Mrcio Antnio Mazutti Sabrina Somacal Claudia Kaehler Sautter 《Molecules (Basel, Switzerland)》2023,28(1)
Consumers increasingly prefer and seek functional beverages, which, given their characteristics, provide important bioactive compounds that help prevent and treat chronic diseases. Mead is a traditional fermented alcoholic beverage made from honey solution. The aging process of mead with oak chips is innovative and bestows functional characteristics to this beverage. Thus, in this study, we sought to develop and characterize a novel functional beverage by combining the health benefits of honey with the traditional aging process of alcoholic beverages in wood. Phenolic compounds, flavonoids, and antioxidant capacity were analyzed in mead using oak chips at different toasting levels and aged for 360 days. LC-ESI-QTOF-MS/MS was used to analyze the chemical profile of different meads. Over time, the aging process with oak chips showed a higher total phenolic and flavonoid content and antioxidant capacity. Eighteen compounds belonging to the classes of organic acids, phenolic acids, flavonoids, and tannins were identified in meads after 360 days. Our findings revealed that the addition of oak chips during aging contributed to p-coumaric, ellagic, abscisic, and chlorogenic acids, and naringenin, vanillin, and tiliroside significantly impacted the functional quality of mead. 相似文献
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Dr. Gabriel Menendez Rodriguez Dr. Francesco Zaccaria Leonardo Tensi Prof. Cristiano Zuccaccia Prof. Paola Belanzoni Prof. Alceo Macchioni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2050-2064
The degradation pathways of highly active [Cp*Ir(κ2-N,N-R-pica)Cl] catalysts (pica=picolinamidate; 1 R=H, 2 R=Me) for formic acid (FA) dehydrogenation were investigated by NMR spectroscopy and DFT calculations. Under acidic conditions (1 equiv. of HNO3), 2 undergoes partial protonation of the amide moiety, inducing rapid κ2-N,N to κ2-N,O ligand isomerization. Consistently, DFT modeling on the simpler complex 1 showed that the κ2-N,N key intermediate of FA dehydrogenation ( INH ), bearing a N-protonated pica, can easily transform into the κ2-N,O analogue ( INH2 ; ΔG≠≈11 kcal mol−1, ΔG ≈−5 kcal mol−1). Intramolecular hydrogen liberation from INH2 is predicted to be rather prohibitive (ΔG≠≈26 kcal mol−1, ΔG≈23 kcal mol−1), indicating that FA dehydrogenation should involve mostly κ2-N,N intermediates, at least at relatively high pH. Under FA dehydrogenation conditions, 2 was progressively consumed, and the vast majority of the Ir centers (58 %) were eventually found in the form of Cp*-complexes with a pyridine-amine ligand. This likely derived from hydrogenation of the pyridine-carboxiamide via a hemiaminal intermediate, which could also be detected. Clear evidence for ligand hydrogenation being the main degradation pathway also for 1 was obtained, as further confirmed by spectroscopic and catalytic tests on the independently synthesized degradation product 1 c . DFT calculations confirmed that this side reaction is kinetically and thermodynamically accessible. 相似文献
6.
Daniela P. Mesquita Cristiano Leal Jorge R. Cunha Adrian Oehmen A. Luís Amaral Maria A.M. Reis Eugénio C. Ferreira 《Analytica chimica acta》2013
The present study focuses on predicting the concentration of intracellular storage polymers in enhanced biological phosphorus removal (EBPR) systems. For that purpose, quantitative image analysis techniques were developed for determining the intracellular concentrations of PHA (PHB and PHV) with Nile blue and glycogen with aniline blue staining. Partial least squares (PLS) were used to predict the standard analytical values of these polymers by the proposed methodology. Identification of the aerobic and anaerobic stages proved to be crucial for improving the assessment of PHA, PHB and PHV intracellular concentrations. Current Nile blue based methodology can be seen as a feasible starting point for further enhancement. Glycogen detection based on the developed aniline blue staining methodology combined with the image analysis data proved to be a promising technique, toward the elimination of the need for analytical off-line measurements. 相似文献
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Alisson J. Santana Denis A. Turchetti Cristiano Zanlorenzi Jos C. R. Santos Edson Laureto Adilson J. A. De Oliveira Leni Akcelrud 《Journal of Polymer Science.Polymer Physics》2019,57(6):304-311
Poly[9,9′‐dihexylfluorene‐2,7‐diyl)‐6,6″‐(2,2′:6′,2″‐terpyridine)] (LaPPS75) and its complexes with neodymium were synthesized and characterized. Magnetic measurements showed that the noncomplexed polymer presented a ferromagnetic contribution due to the formation of π stacking, and that in absence of those, the ferromagnetic behavior is suppressed. The pristine polymer, the complexed one and a low‐molecular‐weight model compound with the same structure of the complexed site in the parent polymer were studied. The observed behavior found is presented and discussed, the most important finding was that when a conjugated chain is used as a host for the metallic ion, an amplification of four times for the magnetization is achieved, using the same metallic content for complexed polymer and model compound for comparison. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 304–311 相似文献
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Flávia Mafra de Lima Regiane Albertini Yvana Dantas Antonio Luis Maia‐Filho Cristiano de Loura Santana Hugo Caire Castro‐Faria‐Neto Cristiane França Antonio Balbin Villaverde Flávio Aimbire 《Photochemistry and photobiology》2013,89(1):179-188
It remains unknown if the oxidative stress can be regulated by low‐level laser therapy (LLLT) in lung inflammation induced by intestinal reperfusion (i‐I/R). A study was developed in which rats were irradiated (660 nm, 30 mW, 5.4 J) on the skin over the bronchus and euthanized 2 h after the initial of intestinal reperfusion. Lung edema and bronchoalveolar lavage fluid neutrophils were measured by the Evans blue extravasation and myeloperoxidase (MPO) activity respectively. Lung histology was used for analyzing the injury score. Reactive oxygen species (ROS) was measured by fluorescence. Both expression intercellular adhesion molecule 1 (ICAM‐1) and peroxisome proliferator‐activated receptor‐y (PPARy) were measured by RT‐PCR. The lung immunohistochemical localization of ICAM‐1 was visualized as a brown stain. Both lung HSP70 and glutathione protein were evaluated by ELISA. LLLT reduced neatly the edema, neutrophils influx, MPO activity and ICAM‐1 mRNA expression. LLLT also reduced the ROS formation and oppositely increased GSH concentration in lung from i‐I/R groups. Both HSP70 and PPARy expression also were elevated after laser irradiation. Results indicate that laser effect in attenuating the acute lung inflammation is driven to restore the balance between the pro‐ and antioxidants mediators rising of PPARy expression and consequently the HSP70 production. 相似文献