Toward the development of new photolabile protecting groups that can rapidly release bioactive compounds upon photolysis with visible light

The synthesis and characterization of a new photolabile protecting group (caging group) for carboxylic acids, the 2-(dimethylamino)-5-nitrophenyl (DANP) group, is described. This compound has a major absorption band in the visible wavelength region with a maximum near 400 nm (epsilon400 = 9077 M(-1) cm(-1) at pH 7.4 and 21 degrees C). The caging group is attached through an ester linkage to the carboxyl functionality of beta-alanine, which activates the inhibitory glycine receptor in the mammalian central nervous system. Such caged compounds play an important role in transient kinetic investigations of fast cellular processes. Upon photolysis of DANP-caged beta-alanine, the caging group is released within 5 micros. Quantum yields of 0.03 and 0.002 were obtained in the UV region (308 and 360 nm) and the visible region (450 nm), respectively. Laser-pulse photolysis experiments, using 337 or 360 nm light, were performed with the caged compound equilibrated with HEK 293 cells transiently transfected with cDNA encoding the alpha1 homomeric, wild-type glycine receptor. The experiments demonstrated that neither DANP-caged beta-alanine nor its byproducts inhibit or activate the glycine receptors on the cell surface. Under physiological conditions, the DANP-caged beta-alanine is water-soluble and stable and can be used for transient kinetic measurements.     

Fragmentation studies on monensin A and B by accurate-mass electrospray tandem mass spectrometry

Monensin A and B were studied by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) and the fragment ions were confirmed by accurate-mass measurements. Analyses were performed on both a quadrupole time-of-flight (QTOF) and a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer. The analysis revealed that fragment ions were produced by Grob-Wharton fragmentations and pericyclic rearrangements in addition to various simple neutral losses. A study of the protonated and sodiated sodium salt revealed different fragmentation pathways for these species, thus complementary structural information could be gained. A complete fragmentation pathway of monensin A and B protonated sodium salt [(M-H+Na)+H])+) and sodiated sodium salt [(M-H+Na)+Na](+) is proposed. MS(3) analysis confirmed the separate fragmentation pathways.     

Simple Conversion of Colchicine into Demecolcine

N-Deacetylcolchiceine ( 7 ), readily available from colchicine ( 1 ), was converted into N-trifluoroacetyl-deacetylcolchiceine ( 8 ). Methylation of 8 with methyl iodide in the presence of potassium carbonate afforded a mixture of N-trifluoroacetyl-demecolcine ( 10 ) and its isomer 11 . The mixture of 10 and 11 was detrifluoroacetylated and separated by chromatography to afford demecolcine ( 2 ) and isodemecolcine ( 12 ). A more practical route to 2 started with 8 , and gave N-trifluoroacetyl-deacetylcolchicine ( 13 ) and its isomer 14 after O-methylation with diazomethane. N-Methylation of 13 and 14 with methyl iodide and potassium carbonate afforded 10 and 11 . The overall yield in the conversion of colchicine ( 1 ) into demecolcine ( 2 ) via 7, 8 and 13 was 55%.     

Einige Verbesserungen von Nachweisen in der organischen Tüpfelanalyse

Zusammenfassung Es werden Verbesserungen von Nachweisen von Alkoholen, Chloral, Salicylalkohol, Salicin, Sulfoxylatverbindungen und bestimmten reduzierenden organischen Verbindungen beschrieben, durch die man zu mikroanalytischer Empfindlichkeit und zum Teil auch zu erhöhter Selektivität gelangt.

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Summary Improvements of tests for alcohols, chloral, salicylalcohol, salicine, sulfoxylate compounds and certain reducing organic compounds are described, which lead to microanalytical sensibility and sometimes also to enhanced selectivity.

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Résumé On décrit des améliorations des méthodes d'identification des alcools, du chloral, de l'alcool salicylique, de la salicine, de composés sulfoxyliques et de combinaisons organiques réductrices définies. Elles atteignent une sensibilité microanalytique et leur sélectivité est parfois accrue.

     

Application of Phosphorus-31 Nuclear Magnetic Resonance Spectrosocopy for the Study of Human Diabetic Cataractogenesis

Intact human Senses incubated at 5.5 mM (normal) and 35.5 mM glucose were examined by phosphorus-31 nuclear magnetic resonance (31P NMR) spectroscopy. Lense in 35.5 mM glucose showed an altered metabolic steady-state characterized by a lowered adenosine triphosphate/inorganic orthophosphate ratio. ³¹P NMR spectroscopy can be used to measure metabolic changes in the lens. This model offers an important means to study dynamic metabolism in the human lens in the setting of diabetic cataractogenesis.     

Die Oxidfluoride des Niobs und Tantals

Oxidefluorides of Niobium and Tantalum The reaction of NbF₅ with SiO₂ (silica glass ampules) at 310°C or with SiO₂ (Aerosil) at 180°C always leads to NbO₂F. To the contrary the reaction with laboratory glass (Jenaer Geräteglas) at 130°C leads to NbOF₃. TaF₅ reacts in silica glass ampules at 400°C by formation of TaO₂F, however at 300°C or 260°C by formation of TaOF₃. Silica glass did not react with NbF₅ at 130°C, however Nb₂O₅ and NbF₅ gave at 130°C in silica glass ampoules NbOF₃. Similarly, TaF₅ and Ta₂O₅ or TaO₂F formed at 260°C in nickel ampoules TaOF₃. The chemical and the thermochemical behaviour of oxidefluorides have been investigated. The compounds NbOF₃ and TaOF₃ are isomorphic. Lattice constants are mentioned.     

Dependence of the activity of a rhizopus lipase on microemulsion composition

Enzymatic hydrolysis of a model triglyceride, palm oil, was carried out with lipase fromRhizopus sp. in microemulsions with varying water content. The microemulsions were based on a nonionic surfactant, pentaethylene glycol monododecyl ether (C12 EO5), buffered water solution and an oil component consisting of isooctane and palm oil at a weight ratio of 20:1. The structure of the microemulsions was characterized using Fourier transform pulsed-gradient spin-echo¹H NMR. The rate of reaction decreased as the water content of the reaction medium was increased. The self-diffusion coefficient of water, D_w was found to be constant within the interval 1–20% water. The difference in reactivity is believed to be due to a difference in structure of the palisade layer between water and hydrocarbon microdomains. The nonionic surfactant was demonstrated to be unsuitable for enzymatic reactions since only partial hydrolysis was obtained in all experiments. The surfactant, however, did not cause enzyme deactivation, even at very high concentrations.     

On the Structure of Syndiotactic Poly(propylenes)

Propylene was polymerized with the catalyst system (C₂H₅)2A1C1/ VCk/ anisole at -78°C using various conditions. The resulting polymers were successively extracted by diethyl ether, hexane, and heptane, leaving the residue. The polymers of the four series were characterized by intrinsic viscosity, gel permeation chromatography, ¹³C nuclear magnetic resonance, infrared spectroscopy, x-ray diffraction, and by differential scanning calorimetry. The combined evidence from the various methods indicates that this catalyst system leads to stereoblock polymers which can be fractionated according to stereochemical composition and sequence length.     

Characterization of Molecular Weight Distributions by the Standard Deviation

The standard deviation [sgrave] is known to be an absolute measure of Gaussian (G) distributions, because it (or multiples of it) always determines a constant fraction of the material. However, this is not true for distribution functions other than Gaussian. The weight fractions corresponding to weight standard deviations (±[sgrave]_w) of Schulz-Flory distributions depend on the polymolecularity index xw/xn, approaching a limiting value of W(x_w ± [sgrave]_w) = 86.5 for x_w/x_n →∞. The use of weight standard deviations is meaningless for generalized logarithmic normal (LN) distributions if x_w/x_n 52. The weight fractions W(X_n ± [sgrave]_n) around the number-average degree of polymerization of G and LN distributions first go through a maximum before decreasing with increasing x_w/x_n. The weight fractions W(x_n ± [sgrave]_n) decrease steadily with higher x_w/x_n.