Precolumn derivatization of nucleotides based on fluorescent carbamate formation of the sugar moieties in high-performance liquid chromatography.

The fluorescence derivatization of nucleotides with 2-(5-chlorocarbonyl-2-oxazolyl)-5,6-methylenedioxybenzo++ furan in the presence of sodium azide and the separation of the derivatives by high-performance liquid chromatography are described. The reagent reacts with 5'-terminal hydroxyl groups of nucleotides to produce the corresponding fluorescent carbamates. The derivatives of mono- and oligonucleotides are separated by chromatography on a reversed phase column (TSKgel ODS-80TM) and the derivatives of octa- and deca-nucleotides on a size exclusion column (TSKgel G3000SWXL). The detection limits (signal-to-noise ratio = 3) are 0.8-6.0 pmol on column. 5'Phosphorylated nucleotide also gives a fluorescent derivative after alkaline phosphatase-mediated dephosphorylation.     

Alternative methods for titratable acidity determination

Methods for determination of titratable acidity, other than traditional titration, i.e. methods without titration, are considered. A number of them use analytical acid-base reagents which quickly convert a mixture of strong and weak acids into a new system. This conversion makes it possible to obtain directly the analytical signal (pH, optical density, etc.) for titratable acidity calculation. These methods in stationary conditions and in flow injection analysis are discussed. Methods not using acid-base reagent (iodide-iodate, chromatographic, spectroscopic and others) are also described. The advantages of the alternative methods such as the decrease labour-consumption and analysis time, simplicity of automation and others are shown.     

Single nanocrystal arrays on patterned poly(ethylene glycol) copolymer microstructures using selective wetting and drying

Single nanocrystal arrays were fabricated on sub-microwells of poly(ethylene glycol) (PEG) copolymer using selective wetting on the hydrophilic regions of the exposed substrate surface and subsequent drying. Templates were produced by molding a thin film of a PEG-based random copolymer on hydrophilic substrates such as glass or silicon dioxide. The polymeric microstructures provide a topographical barrier around the well, which makes it possible to create nanocrystal arrays with controlled geometrical features. The size of the nanocrystal was found to decrease with decreasing well size and also decrease with decreasing topological height. A simple empirical equation was derived to predict the size of the crystal as a function of the pattern size and height, which is in good agreement with the experimental data.     

A new diterpenoid related to eunicellin and cladiellin from a Muricellasp.

The isolation and structure elucidation of a new diterpenoid from a horny-coral (Gorgonaceae) are reported. The ¹H and ¹³C-NMR spectra are discussed.     

Theoretical and experimental studies of the electrochemistry of <Emphasis Type="Italic">p</Emphasis>-aminophenol on a golden electrode

The geometric parameters, vibrational frequencies, and thermochemical values of p-quinonimine (p-AQ) and p-aminophenol (p-AP) were computed ab initio (IIF) and by the density functional theory (DFT) method with the 6-31G(d, p) basis set. Cyclic voltammetry with a golden electrode of p-AP solutions in phosphate buffers at pH 7.30 showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.728 V. The standard electrode potentials of half reactions for p-QI and p-AP were calculated using the free energies and solvation energies of p-QI, p-AP, p-benzoquinone (p-BQ), and hydroquinone (p-HQ). The results showed that the standard electrode potential of half reaction for p-QI and p-AP was 0.743 V at the B3LYP/6-31G(d, p) level and 0.755 V at the HF/6-31G(d, p) level. The standard electrode potentials computed at the B3LYP/6-31G(d, p) and HF/6-31G(d, p) levels were close to their experimental values. The article is published in the original.     

Preparation and properties of a mitomycin C-albumin conjugate

Mitomycin C, an anti-neoplastic agent, was covalently attached to bovine serum albumin through various kinds of spacers such as glutaryl, succinyl, trans-aconityl, methylsuccinyl and the trimellityl group. The prior acylation of albumin not only prevented protein polymerization in the presence of carbodiimide, but also increased the extent of conjugation of the drug. The conjugate of mitomycin C-glutarylated albumin showed the best properties among the conjugates prepared in meeting the requirements for a high yield of nonpolymerized product with an adequately high mitomycin C content and stability as a macromolecular prodrug.     

Determination of citrulline and homocitrulline by high-performance liquid chromatography with post-column derivatization

A high-performance liquid chromatographic method was developed for the determination of citrulline and homocitrulline using a post-column colorimetric reaction with o-phthaladehyde and N-(1-naphthyl)-ethylenediamine. Citrulline and homocitrulline were determined with no interferences from protein amino acids. The results show that the level of citrulline in the plasma of patients with uremia on intermittent hemodialysis is higher than that in healthy human plasma, and that homocitrulline is excreted into the urine of healthy adults.     

Thermodynamics of mixed electrolyte solutions. XI. An isopiestic study of the quaternary system NaCl−KCl−CaCl2−H2O at 25°C

Osmotic and activity coefficients in the aqueous quaternary system sodium chloride-potassium chloride-calcium chloride were derived from isopiestic measurements at 25°C. The isopiestic data were treated by the various procedures of Scatchard, Friedman, and Reilly, Wood, and Robinson. The results obtained showed good agreement with those obtained by pseudo-ternary transforms. Interaction parameters obtained indicated the preponderance of pairwise interactions. Excess Gibbs free energies of mixing were calculated.