NO-hemoglobin may be a light-sensitive source of nitric oxide both in solution and in red blood cells

Hemoglobin in solution and inside red blood cells forms a complex with nitric oxide exhibiting a specific EPR signal both at room and liquid nitrogen temperatures. In the present paper it was shown that the nitrosyl complex of hemoglobin (NO-Hb) is photochemically sensitive and hence may serve as a source of free NO under He-Cd laser irradiation (441 nm). It was found that at laser light radiant power of 3.9 mW, room temperature and in the presence of oxygen, 50% decrease of NO-Hb EPR signal occurred at doses of 54, 30, and 18 kJ/m2 for NO-hemoglobin solution, hemolysed and intact erythrocytes, respectively. The detection of free NO produced as a result of NO-Hb photolysis was performed by means of a spin trap, nitronyl nitroxyl radical NNR, which in the presence of NO is transformed into imino nitroxyl radical (INR) showing different EPR signal. In isolated hemoglobin solution, 20 mM INR was accumulated under irradiation with the maximal dose of 700 kJ/m2. In intact cells the HbFe(2+)-NO photolysis and NO release occur with essentially higher efficacy. To produce 100 mM INR, a dose of 290 kJ/m2 was needed in erythrocyte lysates and 100 kJ/m2 in intact red blood cell suspension. Measurements of absorption spectra showed that in all systems studied (NO-Hb in solution, intact erythrocytes and hemolysed erythrocytes) NO-Hb concentration decreased after irradiation by 14-22% with simultaneous formation of methemoglobin. These observations show that NO-Hb may serve as a store of nitric oxide from which free NO can be released by intensive illumination.     

Cascade rearrangement in the reaction of methyl trifluoropyruvate sulfonylimines with terminal alkynes

Methyl trifluoropyruvate benzene- and methanesulfonylimines react with hex-1-yne and phenylacetylene to give methyl N-sulfonyl-4-oxo-2-trifluoromethyl-4-R-but-2E-enimidates. The reaction mechanism includes the formation of a six-centered bipolar ion followed by its cascade rearrangement.     

Dipole moments of phenyl,benzo, and benzo[b]thiopheno derivatives of thiophene; 1, 4-dithiin,and thianthrene and their sulfones

The dipole moments of a series of phenyl, benzo-, and benzo[b]thiopheno-derivatives of thiophene, 1,4-dithiin, and thianthrene have been determined. An increase in the dipole moments of the phenyl derivatives of thiophene with an increase in the number of phenyl groups is connected with the existence of conjugation between the thiophene and benzene rings, a quantitative evaluation of the nature of which is given. It is suggested that the structure of the 1, 4-dithiin ring is close to coplanar.     

Dipole moments of exciplexes of heteroaromatic compounds with N,N-dimethylaniline

The influence of the polarity of a solvent on the position of the maximum of the fluorescence band of exciplexes of N, N-dimethylaniline (DMA) with exctied molecules of phenazine, acridine, and their benzo-, dibenzo- and tetrabenzo derivatives was studied. From the regularities found, the ²/³h values were evaluated, giving an estimate of the dipole moments of the exciplexes under consideration. An attempt was made to find a correlation between ²/³h values and the value of the enthalpy of formation H of the corresponding excited complexes. It was concluded that for the first members of the azine series, the ²/³h value does not reflect the degree of charge transfer in the exciplex, and cannot be correlated with AH. Explanations are presented which give as the main reason for this lack of correlation the possible conformational changes undergone by the excited molecules of azines during the formation of the exciplexes.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 4, pp. 484–488, July–August, 1985.     

Role of the vibrational coupling of 3nπ* and 3ππ* states in reactions resulting in the formation of triplet exciplexes of phenazine compounds with dimethylaniline

The relationship between the nature of the reactive triplet state of phenazine, as well as its mono-, di-, and tetrabenzo derivatives, and their reactivity in the formation of triplet exciplexes with amines has been investigated. It has been shown that the reactivity of triplet excited states of phenazines is determined mainly by the presence of vibrational mixing of the lower T₁ and T₂ triplet states with different electronic configurations (of the n^* or ^* type) and the position of the T₂ level. The total reaction rate is determined by the sum of the rates of the processes with the participation of the T₁ and T₂ states.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 22, No. 3, pp. 291–296, May–June, 1986.     

Kinetics of nonresonant vibrational energy exchange in binary mixtures of molecular gases

The variation of the temperature of a gas during vibrational relaxation is a unique source of information on the kinetics of vibrational-vibrational (VV) and vibrational-translational (VT) energy exchange, and the characteristic parameters of the temperature curve are related to the characteristic times of the VV and VT processes. The effect of kinetic cooling, in which VV exchange leads to a temperature drop, has been studied quite extensively [1]. It was shown in [2] that the characteristic parameters of the cooling curve are uniquely related to the VV and VT relaxation times.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 15–18, October, 1988.     

Anomalies in the twist elastic behaviour of mixtures of calamitic and bent-core liquid crystals

ABSTRACT

The splay, twist and bend elastic constants (K₁₁, K₂₂ and K₃₃) have been measured as a function of temperature in bent-core/calamitic mixtures based on three different calamitic materials (5CB, 8CB and ZLI1132) and two bent-core dopants. The behaviour of the splay and bend constants are as expected; a reduction in K₃₃ of ~20%, in line with predictions from mixing rules and other observations. Interestingly, no change is seen in the splay constant, K₁₁ of the calamitic hosts. Surprisingly though, the twist elastic constant exhibits a reduction of 30 – 40% in all mixtures across the nematic range, an effect not previously reported and much larger than mixing rules can explain. The elastic behaviour is universal in our mixtures. We explain part of the reduction in the twist deformation by considering the influence of the chiral conformer fluctuations of the bent-core molecules on the twist elastic constants of the mixtures. However, the dramatic reduction can only be fully explained by also including contributions from chiral conformer fluctuations of the calamitic host, a form of chiral amplification.     

Formation of Consolidated Bed by Carbon Sorbent and Oil in Removal of Spilled Oil

Formation of a consolidated bed by carbon sorbent and oil in sorption removal of spilled oil was observed and substituted experimentally; the dynamics of this process was analyzed. A process for eliminating oil spills on the water surface using a carbon sorbent was developed.     

Orientation effects in fluorescence quenching for adsorbed aromatic hydrocarbons

Fluorescence quenching by a potential electron donor or acceptor has been examined for an aromatic hydrocarbon adsorbed on aerosil, for which unusual temperature effects have been observed, where the process is dependent on the nature of the quencher. These phenomena are examined in terms of reaction stereospecificity. By this is meant the resultant displacement from a series of jumps between localization positions. Surface Chemistry Institute, Ukrainian National Academy of Sciences, Prospekt Nauki 31, 252039 Kiev, Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 1, pp. 12–16, January–February, 1997.