Search results for "Molecular chemistry"
showing 10 items of 1103 documents
A Simple System Based on a Thiourea-Modified Fluorescein for ω-Amino Acid Discrimination
2015
A thiourea-modified fluorescein derivative was synthesized by reaction of fluorescein isothiocyanate with 2-(2-aminoethoxy)ethan-1-ol. UV/Vis absorption and fluorescence emission spectroscopy studies demonstrated that this heteroditopic receptor was able to discriminate among linear aliphatic ω-amino acids with different chain lengths.
Rheological modifiers based on supramolecular block copolymers: From weak associations to interconnected micelles
2019
Abstract The rheological spectra of poly(n-butyl acrylate) in the presence of a series of P(nBA-b-HEMA) rheology modifiers show a two-step relaxation process originating from the PnBA matrix and the self-assemblies. The HEMA segments are further grafted with strong, hydrogen bonding UPy groups, which both magnifies and slows down the relaxation of the assemblies. The extents of associations are enlightened by studying thermal transitions in DSC, morphological developments by SAXS, and description of rheological properties using a tube-based model. It is revealed that a weak association tendency, due to long hydrophobic blocks, leads to the formation of double-linear or star assemblies, whil…
Evaluation of Antimicrobial Activity of Triphala Constituents and Nanoformulation
2020
The prevalence of nosocomial infections due to multidrug resistant (MDR) bacterial strains is associated with high morbidity and mortality. Folk medicine and ethnopharmacological data can provide a broad range of plants with promising antimicrobial activity. Triphala, an Ayurvedic formula composed of three different plants: Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb. (Combretaceae), and Phyllanthus emblica L. (Phyllanthaceae), is used widely for various microbial infections. Various extraction techniques were applied in the extraction of the biologically active constituents of Triphala in order to compare their efficiency. Microwave-assisted extraction (MAE) was shown to …
Fluorescent Probes for Ecto-5′-nucleotidase (CD73)
2020
[Image: see text] Ecto-5′-nucleotidase (CD73) catalyzes the hydrolysis of AMP to anti-inflammatory, immunosuppressive adenosine. It is expressed on vascular endothelial, epithelial, and also numerous cancer cells where it strongly contributes to an immunosuppressive microenvironment. In the present study we designed and synthesized fluorescent-labeled CD73 inhibitors with low nanomolar affinity and high selectivity based on N(6)-benzyl-α,β-methylene-ADP (PSB-12379) as a lead structure. Fluorescein was attached to the benzyl residue via different linkers resulting in PSB-19416 (14b, K(i) 12.6 nM) and PSB-18332 (14a, K(i) 2.98 nM) as fluorescent high-affinity probes for CD73. These compounds …
Variability of Hypericins and Hyperforin in Hypericum Species from the Sicilian Flora
2019
Within Sicilian flora, the genus Hypericum (Guttiferae) includes 10 native species, the most popular of which is H. perforatum. Hypericum's most investigated active compounds belong to naphtodianthrones (hypericin, pseudohypericin) and phloroglucinols (hyperforin, adhyperforin), and the commercial value of the drug is graded according to its total hypericin content. Ethnobotanical sources attribute the therapeutic properties recognized for H. perforatum, also to other Hypericum species. However, their smaller distribution inside the territory suggests that an industrial use of such species, when collected from the wild, would result in an unacceptable depletion of their natural stands. This…
Layer-by-Layer Adsorption: The Solid/Liquid-Interface as a Template for the Controlled Growth of Well-Defined Nanostructures of Polyelectrolytes, Pro…
1994
This report describes the construction of ultrathin films whose structure can be tailored on the molecular scale. The resulting supramolecular film architectures may include functional biological macromolecules such as proteins or polynucleotides. The average distances of two functional layers can be adjusted on the nanometer scale (from less than lnm to several tens of nanometers), with a precision of approximately 0.1 nm. This control is achieved by varying the number and the thickness of the polyelectrolyte interlayers and requires the capability of steering each adsorption step with high accuracy. A crucial factor is the fabrication and manipulation of the film surface at each adsorptio…
Formation of supramolecular aggregates by hydrogen bonding based on bispyrimidine and bisbarbituric acid
1997
Hydrogen bonds between bispyrimidine and bisbarbituric acid in equal molar ratio can lead to the formation of supramolecular aggregates. This is established by TEM, IR and DSC measurements. Additionally, WAXS pattern showed that the aggregate is of laminar structure. Both the hydrolysis of this system and termination of the aggregate's growth were studied.
Synthesis of 2-Prenylated Alkoxylated Benzopyrans by Horner–Wadsworth–Emmons Olefination with PPARα/γ Agonist Activity
2021
[Image: see text] We have synthesized series of 2-prenylated benzopyrans as analogues of the natural polycerasoidol, a dual PPARα/γ agonist with anti-inflammatory effects. The prenylated side chain consists of five or nine carbons with an α-alkoxy-α,β-unsaturated ester moiety. Prenylation was introduced via the Grignard reaction, followed by Johnson–Claisen rearrangement, and the α-alkoxy-α,β-unsaturated ester moiety was introduced by the Horner–Wadsworth–Emmons reaction. Synthetic derivatives showed high efficacy to activate both hPPARα and hPPARγ as dual PPARα/γ agonists. These prenylated benzopyrans emerge as lead compounds potentially useful for preventing cardiometabolic diseases.
Supramolecular Aggregates in Vacuum: Positively Mono-Charged Sodium Alkanesulfonate Clusters
2010
The formation and structural features of positively mono-charged aggregates of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and sodium methane—(MetS), butane—(ButS) and octane—(OctS) sulfonate molecules in the gas phase have been investigated by electrospray ionization mass spectrometry, energy-resolved mass spectrometry and density functional theory (DFT) calculations. The experimental results show that the center-of-mass collision energy required to dissociate 50% of these mono-charged aggregates scantly depends on the length of the alkyl chain as well as on the aggregation number. This, together with the large predominance of mono-charged species in the mass spectra, was rationalized i…
Unravelling substitution effects on charge transfer characteristics in cocrystals of pyrene based donors and 3,5-dinitrobenzoic acid
2019
Here we report charge-transfer cocrystals composed of pyrene and amino/bromopyrene as π-donors (D) and 3,5-dinitrobenzoic acid (A) as a π-acceptor. The 1 : 1 cocrystals of pyrene/1-aminopyrene adopt a ⋯DADADA⋯ mixed stack arrangement whereas the 2 : 1 cocrystal of 1-bromopyrene and 3,5-dinitrobenzoic acid shows ⋯DDADDA⋯ stacking. Crystallographic, spectral and theoretical studies reveal that the frontier molecular orbital energy level rather than the π-donor strength plays the governing role in predicting charge transfer. In addition, a theoretical study demonstrates that the ambipolar semiconductor nature in cocrystals of the pyrene/aminopyrene donor and the p-type nature of bromopyrene wi…