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Biomedical subjects

A P Savitskii

Publications and source records attributed to A P Savitskii.

7 recordsLinked to original sources
PubMed2000

Fluorescent properties of firefly luciferases and their complexes with luciferin.

Fluorescence of luciferases from Luciola mingrelica (single tryptophan residue, Trp-419) and Photinus pyralis (two tryptophan residues, Trp-417, Trp-426) was studied. Analysis of quenching of tryptophan fluorescence showed that the tryptophan residue conserved in all luciferases is not accessible for charged quenchers, which is explained by the presence of positively and negatively charged amino acid residues in the close vicinity to it. An effective energy transfer from tryptophan to luciferin was observed during quenching of tryptophan fluorescence of both luciferases with luciferin. From the data on the energy transfer, the distance between the luciferin molecule and Trp-417 (419) in the luciferin luciferase complex was calculated: 11-15 A for P. pyralis and 12-17 A for L. mingrelica luciferases. The role of the conserved Trp residue in the catalysis is discussed.

Amino Acids↗
PubMed1999

Fluorescence of tryptophan residues in firefly luciferases and enzyme--substrate complexes.

Quenching of tryptophan fluorescence of Luciola mingrelica (single tryptophan residue, Trp-419) and Photinus pyralis (two tryptophan residues, Trp-417 and Trp-426) luciferases with different quenchers (I-, Cs+, acrylamide) was studied. The conserved Trp-417(419) residue was shown to be not accessible to charged particles, and positively and negatively charged amino acid residues are located in close vicinity to it. We found previously unreported effective energy transfer from this tryptophan to luciferin during the quenching of the tryptophan fluorescence. The distance between the luciferin molecule and Trp-417(419) was calculated: 11-15 and 12-17 A for P. pyralis and L. mingrelica luciferases, respectively. The role of the conserved Trp residue in the catalysis is discussed. ATP and AMP are also quenchers of the tryptophan fluorescence of the luciferases. In this case, an allosteric mechanism of the interaction of Trp-417(419) with an excess of ATP (AMP) is proposed.

Adenosine Monophosphate↗
PubMed1991

Fibre-optic oxygen sensor based on phosphorescence quenching.

A fibre-optic oxygen sensor is described which is based on an oxygen-sensitive luminescent film made from platinum octaethylporphyrin and polystyrene. The luminescence and quenching characteristics of such films were studied for their use in a fibre-optic oxygen biosensor. A prototype oxygen sensor was made from this material, and was tested in aqueous solutions and in the gaseous phase at physiological oxygen concentrations. Measurements of luminescence intensity and decay time were employed to determine oxygen concentration from luminescence quenching. The main working characteristics of this prototype oxygen sensor were studied.

Biosensing Techniques↗
PubMed1991

Flow-injection glucose determination with long-wavelength luminescent oxygen probes.

A flow-injection method for the determination of glucose in serum is presented. It is based on the enzymatic measurement of oxygen consumption detected via oxygen quenching of the luminescence of certain metalloporphyrins. Phosphorescent water-soluble Pt2+ and Pd(2+)-porphyrins have been characterized by luminescence spectroscopy and decay-time measurements in various buffers, and found to be suitable for oxygen detection in biological systems. A new method for the flow-injection analysis of glucose has been developed based on the use of a column of immobilized glucose oxidase and the indicators Pt(2+)-coproporphyrin III and Pd(2+)-coproporphyrin I. The system has been optimized for glucose determination in aqueous samples and in whole serum with the 0.5-200 mM glucose range. Twenty assays can be performed in an hour, and the system has potential for commercial development with biotechnological and medical applications.

Blood Glucose↗
PubMed1990

Photodestruction in vitro of tumour cells sensitized by porphyrins and their conjugates with specific antibodies.

The photodynamic action of a number of carboxylic porphyrins and their covalent conjugates with specific monoclonal IgM antibodies on a human lung adenocarcinoma cell line was studied. All the conjugates showed strong phototoxicity which did not correspond with the phototoxicity of the free porphyrins. Absolute quantum yields of singlet oxygen photogeneration by the porphyrins and their conjugates were obtained and compared with the phototoxicity of the compounds.

Adenocarcinoma↗