Specific binding of low molecular weight ligands with direct optical detection.

The characterization of low molecular weight ligand interaction with receptor molecules is of importance for the investigation of biological processes and for drug research. We report on the investigation of the binding of low molecular weight ligands to immobilized receptors by label-free detection. Reflectometric interference spectroscopy, an optical transducer which allows the monitoring of a few picograms per square millimetre changes in surface coverage, was used to study two model systems. In both cases detection of the binding event was successful. High affinity binding of biotin to immobilized streptavidin was clearly detectable at receptor surface concentrations as low as 1-2 x 10(10) binding sites/mm2. Linear correlation between the receptor surface concentration and the response to biotin binding was observed. Using immobilized DNA, we investigated the binding of common intercalators with respect to kinetics and thermodynamics by evaluation of the association and the dissociation part of the binding curve. Bi-exponential increase and decrease of intercalator loading was observed, indicating complex interaction kinetics. The four structurally different intercalators showed significant distinction in binding kinetics and equilibrium signals. Improvement of experimental parameters is required to obtain more reliable kinetic data.

Laser flow cytometry and cancer chemotherapy: detection of intracellular anthracyclines by flow cytometry.

The intracellular distribution of important chemotherapeutic antibiotics belonging to the anthracycline group (e.g. adriamycin) can be detected by laser flow cytometry. The indirect method is based on the interference of these compounds with the binding of propidium iodide to the nuclear DNA. While in the direct method, the intracellular fluorescence of these antibiotics is excited and detected with a laser beam in a flow system. The present report demonstrates the use of these two methods for intracellular detection and quantitation of a number of important anthracyclines.

[Formation of the anthracycline antibiotics, beromycin and nogalamycin, by a new actinomycete species, Streptomyces glomeratus sp. nov]. / Obrazovanie antratsiklinovykh antibiotikov beromitsina i nogalamitsina novym vidom aktinomitseta Streptomyces glomeratus sp. nov.

Culture 3980 was isolated from a soil sample and described as a new species, Streptomyces glomeratus sp. nov. It was found that the culture produced simultaneously 2 close anthracycline antibiotics, i. e. nogalamycin and beromycin, which were synthesized mainly in the mycelium. S. glomeratus differed from the nogalamycin and beromycin-producing organisms described earlier.