Interaction of anthracycline antibiotics with biopolymers: 9. Comparative study of the interaction kinetics of daunomycin, adriamycin and iremycin with DNA

Interaction of anthracycline antibiotics with biopolymers: Comparative studies of DNA binding and antimicrobial activity of rhodomycin‐type anthracycline antibiotics

“…This assumption was also made for the analysis of the kinetic data. Moreover, the occurrence of two relaxation times in the kinetic experiments is in full agreement with the doublet-closure approximation (FORSTER et al 1984a), because triplet-closure approximation would demand four relaxation times. Table 3 Equilibrium binding parameters of iremycin (WALTER et al 1983), ,!I-rhodomycin-I and ,!I-rhodomycin-11, but with a = 3 base pairs assumed in contrast to Table 2 iremycin p-rhodom.…”

“…Together with the parameters of the corresponding model (dimerization model or binding model) the extinction coefficients of the monomers ern and dimers Ed or of the ligand-DNA complex Eb were determined simultaneously. With the known equilibrium parameters and with given total concentrations of ligand (ct) and polymer (cpt) the kinetic parameters were determined by means of a simulation prodcedure fitting the relaxation curves of temperature-jump experiments (FORSTER et al 1984a by kinetic theory. The antibiotic potency of purified anthracycline antibiotics was determined by means of a standardized agar plate diffusion assay in a partially chemically defined nutrient medium (Niihrbouillon T/G9RMED-ImmUnpraparatC Berlin 25 g/l, agar 9 g/l) seeded with lo7 spores of Bacillus subtillis ATCC 6633 per test plate (34 ml of agar).…”

“…The theoretical background for the evaluation of our experimental data was treated in detail by SCHUTZ et al FORSTER et al (1984a).…”

“…1984a, STUTTER 1978 is based on the assumption of an integer value of a despite the fact, that, mathematically, functions of a are found which are defined and meaningful for any positive value of a. I n kinetics, moreover, the so-called 'closure'-approximation (SCHWARZ 1971, S~LBERBERG et al 1968) is defined only for integer a. A s the exclusion paranieters in Table 2 (FORSTER et al 1984a). The results of our equilibrium studies suggested the existence of only one single binding step.…”

“…Table 4 Dissociation rate constants kn, association rate constants k A = K . k~ and kinetic cooperativity parameter q determined from temperature-jump experiments (FORSTER et al 1984a The results of the above-mentioned simulation procedure were briefly reported by STUTTER et al (1984) and are compiled in Table 4. To get an idea of the quality of the determination of the kinetic parameters by visual inspection, in Fig.…”