Preparation and Characterization of N-4-Nitrophenyl-L-prolinol Nanocrystals in Sol-Gel Matrices

Organic nanocrystals of N-4-nitrophenyl-l-prolinol (NPP) have been grown in sol-gel matrices prepared from silicon alkoxide precursors. Our process is based on the control of the nucleation and growth kinetics of the dye in the pores of dense gels. Nanocomposites gel-glasses are obtained with a high optical quality due to the small size of the nanocrystals (10-20 nm). Differential scanning calorimetry experiments evidenced clearly the melting point of NPP nanocrystals, which is registered 51°C above that of NPP powder. Micro-Raman and solid state NMR spectroscopies allowed us to demonstrate that our nanocrystallization process does not chemically modify NPP molecules. We specified also the nature of interactions existing between the NPP nanocrystals and the xerogels. These strong interactions, which explain the important increase of the melting point of the nanocrystals in comparison to the NPP powder, are hydrogen bonds between nitro groups of NPP and uncondensed silanol functions of the silicate network.     

Synthesis and properties of 1-(6-methoxy)-2-benzothiazolyl)-2-pyridones

Substituted ]-(6-methoxy-2-benzothiazolyt)-2-pyridones were prepared from 2-amino-6-methoxybenzathiazate through N-(6-methoxy-2-benzothiazotyl) cyanvorearmileaznd-3-aryl-N-(6-methoxy-2-benzothiazolyt)-2-cyano-2-propenamides. The cyclization of the latter with malonodinitrile in the presence of piperidine gave the corresponding pyridones. The structures of the synthesized compounds were confirmed by¹H NMR and mass spectral data.Department of Organic Chemistry, Mass Spectrometry Laboratory, Slovak Technical University, 812 37 Bratislava, Slovakia. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1402–1404, October, 1995. Original article submitted August 24, 1995.     

Determination du plomb dans l'urine par spectrophotometrie d'absorption atomique

Lead is assayed in urine by atomic absorption spectrophotometry after separation by coprecipitation with a CaCO₃, HCl, (NH₄)₂HPO₄ solution at pH 9. Concentration of lead and removal of interfering substances are achieved simultaneously. Fresh or old urine samples acidified with HNO₃ and thymol can be used. Precipitation is quantitative. The precision of the method is ±0,004 ppm of lead.     

The Effects of Methylene Blue and Oxygen Concentration on the Photoinactivation of Qβ Bacteriophage

Abstract— Concentration effects of methylene blue (MB) and oxygen on the photoinactivation rate of Qβ bacteriophage were examined. The effect of initial virus concentration was verified on the similar f2 phage. The inactivation rate, k , is an increasing function of MB and O₂ concentration and shows saturation with respect to MB concentration. Thus the results suggest that MB must adsorb to Qβ sites and oxygen must be present for photoinactivation to occur. The inactivation rate is independent of the initial number of phage particles present before inactivation, indicating that inactivation does not depend upon interaction among viral particles or on surface effects. The results indicate that at least two different viral phenotypes exist within the wild-type Qβ and f2 populations: one susceptible and the other resistant.     

Prostaglandin D2 synthase and its post-translational modifications in neurological disorders

Prostaglandin D2 synthase (PGDS) (beta-trace protein) is a highly abundant cerebrospinal fluid (CSF) glycoprotein. A number of studies have been performed to determine the potential value of this protein for the diagnosis of various neurological disorders. The measurement of total PGDS levels in CSF has proved marginally useful for this purpose, but promising results were obtained while investigating changes in the posttranslational modifications (PTM) pattern. Using 2-DE analysis, we previously showed that PGDS is differentially expressed in ante- and post mortem CSF samples. In the present study, we examined whether the PGDS isoforms may help to distinguish stroke and neurodegenerative disease patients from healthy subjects. The pattern of PGDS PTM was analyzed in CSF from patients with various neurological disorders (n = 44) using IEF/immunoblotting techniques. Strong alterations of this pattern were detected in patients with different forms of degenerative dementia. These findings are consistent with PGDS being altered in some neurological diseases and provide new opportunities for clinical applications.     

β‐Amino Alcohol Properfumes

Amino‐alcohol derivatives of fragrant, volatile aldehydes and ketones were synthesized in a one‐pot procedure by sequential cyanohydrin formation with trimethylsilyl cyanide and reduction with lithium aluminium hydride, or by ammonolysis of epoxide precursors. The amino alcohols are nonvolatile, stable properfumes releasing fragrant carbonyls by oxidation with sodium periodate or sodium bismuthate. Examples include amino alcohol properfumes of citronellal, Lilial^®, lauryl aldehyde, menthone, benzaldehyde, and anisaldehyde.     

A theoretical study of the formation of the parent phosphinine C5H5P from the flash vacuum thermolysis of diallylvinylphosphine

The gas-phase decomposition of diallylvinylphosphine 1 into C5H5P 12 is studied by DFT/6-311+G(d,p) calculations with the B3LYP functional, followed by single-point energy-only calculations at the CCSD(T)/6-311+G(d,p) level. According to these calculations, the first step involves a retro-ene elimination that yields 3-phosphahexatrienes 2Z and 2E. Both compounds equilibrate through the formation of 1,2- and 3,4-dihydrophosphetes 3 and 4, and it is shown that the formation of 2Z is favored by the exothermic formation of the 3,4-dihydrophosphinine 5 through a 6pi-electrocyclization. Though 5 can easily isomerize into 2,3- (6) and 1,2-diyhydrophosphinines (7) by successive 1,5-hydrogen shifts, the formation of 12 from 5, 6, or 7 through an elimination of H2 is found to be a high energy process. It is also shown that the elimination of H2 from lambda5-phosphinine 8 following a C2v pathway is a symmetry-forbidden process. Finally, 1,4-dihydrophosphinine 9, which can be formed through a 1,4-hydrogen shift from lambda5-phosphinine 8, is found to be a convenient precursor of 12 through a 1,4-elimination of H2. The formation of 9 from 5 involves the intermediary formation of 3-phosphabicyclo[3.1.0]hex-2-ene 10. The mechanism eventually proposed for the formation of 12 from 2Z is given in Scheme 16 at the CCSD(T) level.     

Amperometric flow-injection method for the assay of l-ascorbic acid based on the photochemical reduction of Methylene Blue

Ascorbic acid (AA) is determined by amperometric detection based on the photochemical reduction of Methylene Blue (MB(+)) in 0.1 M phthalate buffer at pH 3.8. In this medium, MB(+) using flow-injection analysis. The carrier stream is 1 mM MB(+) is reduced quasi-reversibly at a glassy carbon electrode at -0.34 V vs. Ag/AgCl, while AA is oxidized irreversibly at about 0.3 V. The reactor is irradiated with a 500 W halogen lamp to facilitate the development of the photochemical reaction. A laboratory-built wall-jet electrode system was used. The Leucomethylene Blue formed in the reaction is detected at +0.050 V. At 2.2 ml min(-1) and using a sample loop of 43 mul, the method allows the determination of AA in the range 5.0-90.0 mug ml(-1), with a relative standard deviation of 1.3-4.8%, a detection limit of 1.9 mug ml(-1) and a sampling frequency of 45-50 h(-1).     

Immobilization of protein on ferromagnetic Dacron

Ferromagnetic Dacron (polyethyleneterephthalate) is proposed as a matrix to immobilize proteins covalently. Dacron in powder was magnetized by reacting ferrous (Fe+2) and ferric (Fe+3) ions with its hydrazide form at pH 8.3. Ferromagnetic hydrazide Dacron was converted to ferromagnetic azide Dacron and amyloglucosidase (E.C. 3.2.1.3) was covalently bound through the latter group. The catalytic property of the enzyme was preserved (8% of the specific activity estimated for the soluble enzyme) and all the magnetic amyloglucosidase Dacron derivative was recovered by using a magnetic field. No activity was detected in the supernatant.     

New mono- and bis-carbene samarium complexes: synthesis, X-ray crystal structures and reactivity

New samarium carbene complexes have been synthesized and characterized by X-ray diffraction analysis; the carbenic nature was assessed by reactivity studies.