Spectrophotometric Study of Luminol in Dimethyl Sulfoxide–Potassium Hydroxide

The spectrophotometric study of luminol (LH₂) in dimethyl sulfoxide (DMSO), DMSO-water solutions, and alkaline DMSO and DMSO-water solutions has been done, focusing on the effect of the KOH additon on LH₂ absorption and fluorescence properties. The absorption spectra indicate an acid-base equilibrium, and the luminol dianion (L^2–) formation at 3 × 10^–4 – 2.4 × 10^–3 M KOH. The decrease of the fluorescence intensity and the variation of the excitation spectra of LH₂-DMSO-KOH solutions with KOH concentration have been similarly explained. The acid-base process is reversible. The addition of HCl to the solution with 3.0 × 10^–3 M KOH leads to an increase of the fluorescence intensity to its highest value, observed in pure DMSO. The addition of HCl to the LH₂-DMSO solution leads to the decrease of the fluorescence intensity as a result of the LH⁺ ₃ cation formation. In LH₂-DMSO-water, the fluorescence band is shifted from 405 nm to 424 nm and increased in the intensity. In the presence of KOH (in LH₂-DMSO-water-KOH solution) a new band appears, with the maximum at 485 nm and the band at 405 nm decreased. The changes in fluorescence lifetimes also evidence the different chemical species formed.     

Synthesis and transformation of N-oxides of some imidazo[4,5-b]pyrazine derivatives

The Böckelheide reaction was accomplished with a number of imidazo[4,5-b]pyrazine N-oxides, and the N-oxidation of the resulting acetoxy(hydroxy)methyl derivatives of imidazo[4,5-b]pyrazine and 6-bromo-1-methylimidazo[4,5-b]pyrazine was studied. The hydrolytic cleavage of 6-bromo-1-methylimidazo[4,5-b]pyrazine and its 4-N-oxide was studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 690–693, May, 1975.     

PHOTODYNAMIC RELEASE OF PROTOPORPHYRIN FROM INTACT ERYTHROCYTES IN ERYTHROPOIETIC PROTOPORPHYRIA: THE EFFECT OF SMALL REPETITIVE LIGHT DOSES

Abstract— Erythrocytes from patients with erythropoietic protoporphyria contain large amounts of protoporphyrin bound to (hemo)globin. Irradiation of these cells causes a shift in fluorescence emission maximum and a decreased fluorescence intensity which is consistent with transfer of protoporphyrin from (hemo)globin to the cell membrane. When the erythrocytes were irradiated intermittently, nearly 70% of the protoporphyrin was released and the hemolysis was less than 3%. Giving the total light dose as a single pulse, resulted in 84% protoporphyrin release and 16% hemolysis.
In vivo the erythrocytes obtain small, repetitive light doses when circulating in the dermal capillaries. We suggest the possibility that in patients with erythropoietic protoporphyria these small light pulses could be sufficient to photodamage the binding place of protoporphyrin on (hemo)globin. In the dark, protoporphyrin can then move from (hemo)globin through the cell membrane and bind to albumin in the serum. Our findings indicate that if protoporphyrin is not present in the cell membrane during irradiation, no photohemolysis will occur. This may explain why patients with erythropoietic protoporphyria have no abnormal hemolysis. The effect of intermittent light pulses may also contribute to the understanding of the protoporphyrin release from erythrocytes in patients with erythropoietic protoporphyria.     

Study of the nucleophilic substitution reactions of 2,4,10-trichloropyrimido[5,4-b]quinoline

A number of pyrimido[5,4-b]quinoline derivatives were synthesized. It is shown that in the reaction of 2,4,10-trichloropyrimido[5,4-b]quinoline (II) with strong nucleophilic reagents (OCH₃ and SH) both of the halogens of the pyrimidine ring are replaced, while with amines substitution of the halogens of the pyrimidine ring proceeds successively; under more severe conditions, all three halogen atoms of II are replaced by amine residues.     

Preliminary characterization of anhydrous ethanol used in Brazil as automotive fuel

This work reports preliminary studies on the characterisation of anhydrous ethanol (AEA) used as an automotive fuel mixed with gasoline in Porto Alegre (South Brazil). Pre-concentration of the impurities contained in 1000 ml of AEA was carried on through solid-phase extraction using XAD4 resin. The main compounds in the extract were identified by means of spectral data from the library of the equipment. The concentrate was then fractionated using a preparative liquid chromatographic column filled with activated silica gel and the elution procedure was carried out with, n-hexane, n-hexane-benzene (1:1, v/v) and dichloromethane. Prior to analysis by GC-MS, each fraction was reduced to 1 ml with a gentle stream of nitrogen. Saturated linear hydrocarbons and aromatic hydrocarbons eluted in the first fraction and oxygenated compounds such as aldehydes. ketones and alcohols, eluted in the second one. were the main compounds detected in the sample.