On the use of the spectral luminescent method for studying acid-base equilibria of uracil derivatives in aqueous solutions.

The effect of pH on fluorescence parameters (spectral composition, intensity I, and quantum yield φ) of thymine (T), 5-fluorouracil (FU) and 6-aminouracil (AU) have been investigated in aqueous solutions. As found, there is the regularity of the changes in the spectral composition, intensity, and quantum yields of uracil fluorescence depending on pH. The constants of the acid-base equilibria of uracils (pK) determined by the fluorescence titration method are: 9.

Theoretical Models for Quantitative Description of the Acid-Base Equilibria of the 5,6-Substituted Uracils.

The acidities of 18 5,6-substituted uracils have been numerically estimated as pK values in terms of three theoretical models. The first scheme includes the calculation of the gas-phase acidity of uracil with the G3MP2B3 method and taking into account the solvent effect using the polarizable continuum approximation PCM(SMD)-TPSS/aug-cc-pVTZ. The second model is one step and implies calculation of the free Gibbs energies of the hydrate complex of uracil (and its anion) with 5 water molecules by the TPSS/aug-cc-pVTZ method.

Analysis of binding ability of two tetramethylpyridylporphyrins to albumin and its complex with bilirubin.

An interaction between 5,10,15,20-tetrakis-(N-methyl-x-pyridyl)porphyrins, x=2; 4 (TMPyPs) with bovine serum albumin (BSA) and its bilirubin (BR) complex was investigated by UV-Viz and fluorescence spectroscopy under imitated physiological conditions involving molecular docking studies. The parameters of forming intermolecular complexes (binding constants, quenching rate constants, quenching sphere radius etc.) were determined.

Aza-Michael reaction of 12-N-carboxamide of (-)-cytisine under high pressure conditions.

The first example of aza-Michael reaction of 12-N-carboxamide of quinolizidine alkaloid (-)-cytisine with α,β-unsaturated ketones, dimethyl acetylenedicarboxylate and β-nitrostyrene under high pressure condition has been described. It has been shown that the [4+2]-cycloaddition takes place in the case with N-phenylmaleimide.

Thermodynamics of organic molecule adsorption on sorbents modified with 5-hydroxy-6-methyluracil by inverse gas chromatography.

The thermodynamic features of organic molecule adsorption from the gaseous phase of sorbents modified with 5-hydroxy-6-methyluracil (HMU) were studied. Molar internal energy and entropy of adsorption variation analyses showed that with every type surface, except for silica gel, layers of supramolecular structure have cavities equal in size with the ones revealed in HMU crystals by X-ray diffraction. Adsorption thermodynamics on HMU-modified sorbents depended on the amount of impregnated HMU and on the polarity, but not the porosity, of the initial sorbent.

Spectroscopic studies of the supramolecular interactions between uracil and 5-hydroxy-6-methyluracil with bovine serum albumin and its bilirubin complex.

Using fluorescence and absorption spectroscopy the interaction of bovine serum albumin and its bilirubin complex with uracil and 5-hydroxy-6-methyluracil in phosphate buffer at pH 7.4 was investigated. The parameters of forming intermolecular complexes (binding constants, quenching rate constants, the radius of the quenching sphere and etc.

Nesting biology of Paravespa rex (von Schulthess 1924) (Hymenoptera: Vespidae: Eumeninae) in the Crimea, Ukraine.

Paravespa rex is the only species of the wasp genus Paravespa that occurs in Europe. Females of this species nest in clay loam soil of proluvial terraces and deluvial aprons of badlands. The nests are vertical burrows 10-12 cm deep, surmounted by turrets of two distinct architectural forms: funnel-shaped and curved.