Binding of metal ions to polysaccharides. V. Potentiometric, spectroscopic, and viscosimetric studies of the binding of cations to chondroitin sulfate and chondroitin in neutral and acidic aqueous media.

Binding of cations to chondroitin sulfate A and C, chondroitin, and D-glucuronate was investigated in neutral and acidic aqueous media using H+, Cu2+, and Na+ ion-specific electrodes, viscometry, electron spin resonance (esr), and ligand-field spectroscopy. Site binding to the carboxylate group and only electrostatic interaction with the sulfate group could describe the results well. The nitrogen atom of the N-acetyl group appeared not to be involved in bonding of cations to chondroitin(sulfate) systems. The interaction of the divalent metal ions follows the Irving-Williams series. The value of the electrostatic potential at the carboxylate group of chondroitin(sulfate), as experienced by a cation, was determined in dependence of cation bonding. It proved to be difficult to establish the composition of a complex of a metal ion with a polyion by means of a molar ratio curve.

A 13C-n.m.r. study of the binding of ytterbium(III) to chondroitin sulphate and chondroitin.

13C-N.m.r. spectra of chondroitin 4- and 6-sulphates, chondroitin, beta-D-glucuronate, and beta-D-glucose 6-sulphate were measured in the presence of ytterbium(III) in deuterium oxide. The structure of the ytterbium-polysaccharide compounds in solution was found to be similar to that reported for calcium chondroitin 4-sulphate in a stretched film. In the glucuronate complex, Yb(III) coordinates to the carboxylate group. For beta-D-glucose 6-sulphate, the ytterbium-induced shifts are too small to allow the structure to be determined.

Mechanism of action of the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline on Mycoplasma gallisepticum.

Evidence was found that the inhibitory action of Cu(DMP)2NO3, the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline (DMP), on Mycoplasma gallisepticum is a consequence of the ultimate toxicity of copper, and not that of the ligand, DMP. From uptake studies with radiolabeled 67Cu and [14C]DMP, we concluded that significantly more copper than DMP is bound to the mycoplasmal cell. It appeared that dissociation of Cu(DMP)2+ occurred shortly after interaction with the cell membrane. Copper was transported across the cytoplasmic membrane. A strong dependence of copper uptake on the incubation medium was observed in the absence of DMP. The main function of the ligand DMP appeared to be as a vehicle for the transport of copper from nontoxic copper-medium complexes to membrane-buried cellular ligands.

Mode of action of the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline on Mycoplasma gallisepticum.

Various physiological important activities of Mycoplasma gallisepticum were inhibited by the copper(I) complex of 2,9-dimethyl-1,10-phenanthroline [Cu(DMP)2NO3]. The energy-yielding metabolism was inhibited because the conversion of pyruvate into lactate was found to be blocked by Cu(DMP)2NO3, indicating a selective inhibition of lactate dehydrogenase. Also, the production rate of acetate and the rate of oxygen uptake by whole cells of M. gallisepticum appeared to be strongly decreased. Experiments with crude cell extracts showed an inhibition of reduced nicotinamide adenine dinucleotide (NADH) oxidase by Cu(DMP)2NO3 and an even stronger inhibition of NADH oxidase and lactate dehydrogenase by CuSO4. No preferential inhibition of adenosine 5'-triphosphatase and pyruvate kinase was found. Investigations on the influence of Cu(DMP)2NO3 on deoxyribonucleic acid, ribonucleic acid, and protein synthesis with growing cells of M. gallisepticum showed a selective inhibition of the incorporation of [14C]thymidine into deoxyribonucleic acid. Cu(DMP)2NO3 induced a decrease in the total amount of accessible sulfhydryl groups of whole cells of M. gallisepticum, indicating that the observed diverse toxicity of Cu(DMP)2NO3 may be associated with the interaction of copper ions with protein sulfhydryl groups.

Mode of action of copper complexes of some 2,2'-bipyridyl analogs on Paracoccus denitrificans.

Copper complexes of 2,2'-bipyridyl and related compounds and CuSO4 inhibited the growth of paracoccus denitrificans. The copper(I) complex of 2,9-dimethyl-1,10-phenanthroline [Cu(DMP)2NO3] showed the highest activity, whereas the copper(II) complex of 1,10-phenanthroline and CuSO4 inhibited the growth to a lesser extent. The uncomplexed ligands (1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline) showed little activity, but in the presence of noninhibitory amounts of CuSO4 this activity increased markedly. Copper ions therefore proved to be essential for the growth-inhibitor effect. The extent of inhibition appeared to be strongly dependent on the initial cell density and on the growth medium. No selective inhibition of deoxyribonucleic acid, ribonucleic acid, or protein synthesis was observed with Cu(DMP)2NO3. Respiratory electron transport of P. denitrificans appeared to be strongly inhibited by Cu(DMP)2NO3 and to a somewhat lesser extent by CuSO4. Both aerobic and anaerobic respirations were inhibited to the same extent, and from the cytochrome redox kinetics it is concluded that the site of this inhibition in the respiratory electron transport chain must be located before cytochrome b. Cu(DMP)2NO3 did not significantly influence the H+/O ratio with whole cells of P. denitrificans, suggesting that the efficiency of oxidative phosphorylation is not affected by CU(DMP)2NO3. Growing cultures of P. denitrificans showed a decrease in intracellular potassium ion content in the presence of increasing amounts of Cu(DMP)2NO3. It is concluded that interference with the cytoplasmic membrane, resulting in inhibition of respiratory electron transport, probably constitutes the main mode of action of copper complexes of 2,2'-bipyridyl analogs on P. denitrificans.