Fabrication and drug release behavior of ionically cross-linked chitosan microspheres

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Behavior of double stimuli-responsive copolymer of N-(3-(diethylamino) propyl)-N-methylacrylamide and N,N–diethylacrylamide in aqueous solutions

Double stimuli-responsive copolymer of N-(3-(diethylamino)propyl)-N-methylacrylamide and N,N-diethylacrylamide (molar mass M ≈ 32,000?g?mol^?1) in buffer solutions was studied by the static and dynamic light scattering and turbidimetry. The experiments were performed within pH interval from 7 to 13 and in a wide concentration range. Two types of scattering species were observed in solutions of all concentrations and pH at room temperatures. They were macromolecular unimers and loose aggregates. The increase in concentration and pH led to decrease in phase separation temperatures and width of phase transition.     

Crystal structures of mono- and binuclear neodymium diarylphosphate complexes and their catalytic activity in 1,3-diene polymerization

Structural Chemistry - Molecular structures of three neodymium tris(organophosphate) complexes of different types have been determined: mononuclear complex...     

Bis(trifluoromethyltellurato(0))metallates(I) of copper, silver and gold, [M(TeCF3)2] (M = Cu, Ag, Au)

Ligand exchange reactions of [NMe₄]TeCF₃ and CuBr, Ag[BF₄] and AuCl have been studied in molar ratios of 2:1. While evidence is found for [Cu(TeCF₃)₂]⁻ moieties by ¹⁹F-NMR spectroscopic and mass spectrometric means, [NMe₄][Ag(TeCF₃)₂] and [NMe₄][Au(TeCF₃)₂] were isolated. After cation exchange, the latter compounds were fully characterised as the [PNP] salts ([PNP] = bis(triphenylphosphoranylidene)ammonium). The single crystal structure of [PNP][Au(TeCF₃)₂] has been elucidated by XRD measurements (P2₁/a; a = 1765.6(1), b = 1126.0(1), c = 2055.2(1) pm; β = 111.98(1)°; Z = 4).     

New nitric oxide-carrier systems based on an amphiphilic copolymer of N-vinylpyrrolidone with triethylene glycol dimethacrylate

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3‐(α‐Chlorobenzyl)quinoxalin‐2(1H)‐ones as Versatile Reagents for the Synthesis of 3‐Benzylquinoxalin‐2(1H)‐ones and Thiazolo[3,4‐a]quinoxalin‐4(5H)‐ones

Facile and efficient methods for the synthesis of 3‐benzylquinoxalin‐2(1H)‐ones and thiazolo[3,4‐a]quinoxalin‐4(5H)‐ones by the reaction of the readily available 3‐(α‐chlorobenzyl)quinoxalin‐2(1H)‐ones and thiourea have been developed, with multiple roles of the latter. Possible mechanisms are discussed. These two‐step sequences can be performed in a one‐pot manner to produce the desired products in moderate to high yields.     

Stepwise Hydride Transfer in a Biological System: Insights into the Reaction Mechanism of the Light‐Dependent Protochlorophyllide Oxidoreductase

Hydride transfer plays a crucial role in a wide range of biological systems. However, its mode of action (concerted or stepwise) is still under debate. Light‐dependent NADPH: protochlorophyllide oxidoreductase (POR) catalyzes the stereospecific trans addition of a hydride anion and a proton across the C₁₇?C₁₈ double bond of protochlorophyllide. Time‐resolved absorption and emission spectroscopy were used to investigate the hydride transfer mechanism in POR. Apart from excited states of protochlorophyllide, three discrete intermediates were resolved, consistent with a stepwise mechanism that involves an initial electron transfer from NADPH. A subsequent proton‐coupled electron transfer followed by a proton transfer yield distinct different intermediates for wild type and the C226S variant, that is, initial hydride attaches to either C₁₇ or C₁₈, but ends in the same chlorophyllide stereoisomer. This work provides the first evidence of a stepwise hydride transfer in a biological system.     

Synthesis,molecular structure,conformation and biological activity of Ad-substituted N-aryl-tetraoxaspiroalkanes

An efficient method has been developed for the synthesis of 7′-arylspiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocanes)} by the ring transformation reaction of spiro{adamantane-[2,3’]-(1′,2′,4′,5′,7′-pentaoxacane)} with arylamines in the presence of Sm(NO₃)₃·6H₂O as the catalyst. NMR signals of the synthesized compounds were assigned considering the conformation dynamics of the tetraoxazocane ring with two rigid peroxide bonds. The structures of some of the compounds were studied by X-ray diffraction. The thermal stability of single crystal was determined by DSC method. Compounds 7′-(2-methylphenyl)spiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocane)} and 7′-(4-fluorophenyl)spiro{adamantane-[2,3′]-(1′,2′,4′,5′,7′-tetraoxazocane)} exhibited cytotoxicity towards cancer cells.     

PCl3- and organometallic-free synthesis of tris(2-picolyl)phosphine oxide from elemental phosphorus and 2-(chloromethyl)pyridine hydrochloride

In the superbase KOH/H₂O/toluene/phase-transfer catalyst system, 2-picolyl chloride, generated in situ from 2-(chloromethyl)pyridine hydrochloride, reacts with elemental phosphorus at 65–95?°C for 3?h to afford tris(2-picolyl)phosphine oxide in 50% yield. Single crystal X-ray analysis of the latter revealed one polymorph form of this tertiary phosphine oxide.