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991.
Kevin Doyle Maxine Roberts Jenna Harvey Richard Hewer Matthias Zebisch Victor Rangel Meigang Gu Yiming Wu Lichao Yang Mark Carlton Lee Dawson Roland Bürli 《Helvetica chimica acta》2023,106(9):e202300080
Brain concentrations of nicotinamide adenine dinucleotide (NAD+), an important cellular co-factor, tend to decrease with age and in neurodegeneration. As the NADase cluster of differentiation 38 (CD38) significantly contributes to NAD+ consumption, we reasoned that CD38 inhibition may be of therapeutic value for CNS disorders. The new pyrazole compound was designed based on a known CD38 inhibitor and showed good inhibitory potency. Several attempts to co-crystallise this pyrazole with CD38 and cyclic adenosine diphosphate ribose (cADPR) culminated in a high-resolution X-ray structure, in which the pyrazolyl group in the new compound formed a covalent bond with one of the ribosyl units of cADPR. This reaction proceeded under retention of configuration and resulted in a neutral ribosyl-pyrazole conjugate that is embedded within the active site of the enzyme. An analysis of this structural complex gave rise to design principles that enabled the preparation of more potent CD38 inhibitors with drug-like properties. 相似文献
992.
Alberto Concellón Iván Marín Joaquín Barberá Mercedes Marcos José L. Serrano 《Helvetica chimica acta》2023,106(5):e202300010
We have developed a new strategy for the preparation of a light-responsive ionic liquid crystal (LC) that shows photo-switchable proton conduction. The ionic LC consists of a bowl-shaped calix[4]arene core ionically functionalized with azobenzene moieties. The non-covalent architectures were obtained by the formation of ionic salts between the carboxylic acid group of an azo-derivative and the terminal amine groups of a calixarene core. The presence of ionic salts results in a hierarchical self-assembly process that extends to the formation of a nanostructured lamellar LC arrangement (smectic A phase). In this LC phase, the ionic LC calixarene is able to display proton conductive properties, since the ionic nanosegregated areas (formed by the ionic pairs) generate the continuous channels that favor proton transport. The optical and photo-responsive properties were studied by UV-Vis spectroscopy, demonstrating that the azobenzene moieties of the ionic LC undergo reversible (E)-to-(Z) isomerization by irradiation with UV light. Interestingly, this (E)-to-(Z) photoisomerization results in a decrease of the proton conductivity values since the bent-shaped (Z)-isomer disrupts the lamellar LC phase. This isomerization process is totally reversible and leads to an ionic LC material with unique photo-switchable proton conductive properties. 相似文献
993.
Victor Hugo Infante Patricia Maria Maia Campos Maxim Darvin Silke Lohan Johannes Schleusener Sabine Schanzer Juergen Lademann Martina Meinke 《Photochemistry and photobiology》2023,99(1):176-183
This aim of this study was to evaluate the penetration depth, antioxidant capacity and the clinical efficacy of Melaleuca alternifolia pure essential oil and in a nanoemulsion to prevent skin photoaging. For this, 2% of pure essential oil or 2% of this essential oil in a nanoemulsion were vehiculated in a formulation. The skin penetration was evaluated using confocal Raman microspectroscopy. The radical protection factor was evaluated using electron paramagnetic resonance spectroscopy. For a clinical study, 40 male participants, aged 18–28 years, were enrolled, being divided into three groups: vehicle formulation, M. alternifolia pure essential oil and M. alternifolia Nanoemulsion. All the participants also received a sunscreen SPF 50 to use during the day. Before and after 90 days of study, skin hydrolipidics and morphological characteristics were performed by skin imaging and biophysical techniques. The nanoemulsion presented a lower antioxidant capacity and a higher penetration through the stratum corneum, reaching the viable epidermis, improving the stratum granulosum morphology. The groups presented an increase in the papillary depth, improving in the dermis echogenicity and the collagen fibers. Melaleuca alternifolia essential provides the potential to improve photoaged skin, being the application of nanoemulsion able to reach deeper skin layers. 相似文献
994.
Caetano P. Sabino Martha S. Ribeiro Mark Wainwright Carolina dos Anjos Fábio P. Sellera Milena Dropa Nathalia B. Nunes Guilherme T. P. Brancini Gilberto U. L. Braga Victor E. Arana-Chavez Raul O. Freitas Nilton Lincopan Maurício S. Baptista 《Photochemistry and photobiology》2023,99(2):742-750
The unbridled dissemination of multidrug-resistant pathogens is a major threat to global health and urgently demands novel therapeutic alternatives. Antimicrobial photodynamic therapy (aPDT) has been developed as a promising approach to treat localized infections regardless of drug resistance profile or taxonomy. Even though this technique has been known for more than a century, discussions and speculations regarding the biochemical mechanisms of microbial inactivation have never reached a consensus on what is the primary cause of cell death. Since photochemically generated oxidants promote ubiquitous reactions with various biomolecules, researchers simply assumed that all cellular structures are equally damaged. In this study, biochemical, molecular, biological and advanced microscopy techniques were employed to investigate whether protein, membrane or DNA damage correlates better with dose-dependent microbial inactivation kinetics. We showed that although mild membrane permeabilization and late DNA damage occur, no correlation with inactivation kinetics was found. On the other hand, protein degradation was analyzed by three different methods and showed a dose-dependent trend that matches microbial inactivation kinetics. Our results provide a deeper mechanistic understanding of aPDT that can guide the scientific community toward the development of optimized photosensitizing drugs and also rationally propose synergistic combinations with antimicrobial chemotherapy. 相似文献
995.
In the last decade, planar chiral ferrocenes have attracted a growing interest in several fields, particularly in asymmetric catalysis, medicinal chemistry, chiroptical spectroscopy and electrochemistry. In this frame, the access to pure or enriched enantiomers of planar chiral ferrocenes has become essential, relying on the availability of efficient asymmetric synthesis procedures and enantioseparation methods. Despite this, in enantioseparation science, these metallocenes were not comprehensively explored, and very few systematic analytical studies were reported in this field so far. On the other hand, enantioselective high-performance liquid chromatography has been frequently used by organic and organometallic chemists in order to measure the enantiomeric purity of planar chiral ferrocenes prepared by asymmetric synthesis. On these bases, this review aims to provide the reader with a comprehensive overview on the enantioseparation of planar chiral ferrocenes by discussing liquid-phase enantioseparation methods developed over time, integrating this main topic with the most relevant aspects of ferrocene chemistry. Thus, the main structural features of ferrocenes and the methods to model this class of metallocenes will be briefly summarized. In addition, planar chiral ferrocenes of applicative interest as well as the limits of asymmetric synthesis for the preparation of some classes of planar chiral ferrocenes will also be discussed with the aim to orient analytical scientists towards ‘hot topics’ and issues which are still open for accessing enantiomers of ferrocenes featured by planar chirality. 相似文献
996.
Friedericke S. Menke Dr. Barbara Wicher Dr. Victor Maurizot Prof. Ivan Huc 《Angewandte Chemie (International ed. in English)》2023,62(12):e202217325
Aromatic oligoamide sequences programmed to fold into stable helical conformations were designed to display a linear array of hydrogen-bond donors and acceptors at their surface. Sequences were prepared by solid-phase synthesis. Solution 1H NMR spectroscopic studies and solid-state crystallographic structures demonstrated the formation of stable hydrogen-bond-mediated dimeric helix bundles that could be either heterochiral (with a P and an M helix) or homochiral (with two P or two M helices). Formation of the hetero- or homochiral dimers could be driven quantitatively using different chlorinated solvents—exemplifying a remarkable case of either social or narcissistic chiral self-sorting or upon imposing absolute handedness to the helices to forbid PM species. 相似文献
997.
Dr. Juan P. Mora-Fuentes Marcos D. Codesal Marco Reale Dr. Carlos M. Cruz Dr. Vicente G. Jiménez Dr. Alice Sciortino Prof. Marco Cannas Prof. Fabrizio Messina Dr. Victor Blanco Dr. Araceli G. Campaña 《Angewandte Chemie (International ed. in English)》2023,62(21):e202301356
We report the synthesis and characterization of a novel type of nanohoop, consisting of a cycloparaphenylene derivative incorporating a curved heptagon-containing π-extended polycyclic aromatic hydrocarbon (PAH) unit. We demonstrate that this new macrocycle behaves as a supramolecular receptor of curved π-systems such as fullerenes C60 and C70, with remarkably large binding constants (ca. 107 M−1), as estimated by fluorescence measurements. Nanosecond and femtosecond spectroscopic analysis show that these host-guest complexes are capable of quasi-instantaneous charge separation upon photoexcitation, due to the ultrafast charge transfer from the macrocycle to the complexed fullerene. These results demonstrate saddle-shaped PAHs with dibenzocycloheptatrienone motifs as structural components for new macrocycles displaying molecular receptor abilities and versatile photochemical responses with promising electron-donor properties in host-guest complexes. 相似文献
998.
Ernesto Schulz Lang Gelson Manzoni de Oliveira Bárbara Tirloni Marcos Antonio Villetti 《Journal of Cluster Science》2008,19(3):459-469
(PhTe)2Hg reacts with HgCl2 and triphenylphosphine to give the clusters [(PhTe)6(Ph3P)2Hg5Cl4] · 2THF (1) and [(PhTe)8Hg6Py2Cl4] · Py (Py = pyridine) (2). In 1 each tellurium atom connects two Hg atoms, with Hg–Te distances around 2.75 Å. Phosphorus atoms of the triphenylphosphine groups complete the tetrahedral coordination of the Hg1 atoms. The second set
of Hg atoms (Hg2) is also coordinated to chlorine atoms. The three-dimensional assembling of 1 encloses circular channels with medium diameter of 12.5 Å. The cluster 2 results from substitution of the oxidized triphenylphosphine ligands of 1 by one molecule of Hg(PhTe)2 in the course of the synthetic procedures. The alternated Te–Hg bonds of 2 close a 12-membered ring with two inverted 4-membered rings in the middle. Thermogravimetrical evaluations and Raman scattering
lines of 1 and 2 are also discussed.
相似文献
Gelson Manzoni de Oliveira (Corresponding author)Email: |
999.
A new approach for the collection of aerosol particles is described in which the particles are first collected on a water‐soluble filter and then liberated into an aqueous solution. The filter was manufactured by electrospinning a polyacrylamide (PAA) gel solution containing 2,2′‐(bisacrylamino) diethyl disulfide (BAC) cross‐links after gel dissolution in a water solution of β‐mercaptoethanol. The morphology of the P(AA–BAC) nanofibers was characterized using atomic force microscopy (AFM) and optical microscopy. The filters were characterized for their ability to capture aerosol particles, their stability at high humidity, and their ability to release captured particles. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
1000.
Polo V Andres J Berski S Domingo LR Silvi B 《The journal of physical chemistry. A》2008,112(31):7128-7136
Thom's catastrophe theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C-C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels-Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach. 相似文献