ABSTRACT
The aminoglycosidic antibiotic hygromycin B presents a peculiar chemical structure, characterized by two sugar rings joined via a spiro connection. The Cu(ii) complex of hygromycin B in water solution was characterized by (1)H-NMR, UV-Vis, EPR and CD spectroscopy, combined with potentiometric measurements. The spin-lattice relaxation enhancements were interpreted by the Solomon-Bloembergen-Morgan theory, allowing us to calculate copper-proton distances that were used to build a model of the complex by molecular mechanics and dynamics calculations. The fidelity of the proposed molecular model was checked by ROESY maps. Moreover DNA damage by the Cu(ii)-hygromycin B system was also investigated, showing single and double strand scissions exerted by the complex at concentrations in the range 1-5 mM. Addition of either hydrogen peroxide or ascorbic acid to each sample resulted in the shift of the cleavage potency towards lower concentrations of the complex.
Subject(s)
Anti-Bacterial Agents/chemistry , Copper/chemistry , DNA Damage , Hygromycin B/chemistry , Organometallic Compounds/chemistry , Organometallic Compounds/pharmacology , Hydrogen-Ion Concentration , Molecular Conformation , Molecular Dynamics Simulation , Organometallic Compounds/chemical synthesis , Potentiometry , Protons , Solutions , Spectrum Analysis , Water/chemistrySubject(s)
Anti-Bacterial Agents/chemistry , Nebramycin/analogs & derivatives , Ribosomes/chemistry , Anti-Bacterial Agents/pharmacology , Bacterial Translocation , Binding Sites , Circular Dichroism , Magnetic Resonance Spectroscopy , Nebramycin/chemistry , Nebramycin/pharmacology , Ribosomes/metabolismABSTRACT
The solution structure of kanamycin A interacting with a ribosomal A-site fragment was solved by transferred-NOE techniques and found to agree with the structure of the complex observed in the crystal. Despite the fast exchange conditions found for the interaction, the bound form was identified by NOESY spectroscopy. At 600 MHz, NOE effects are only observed for the RNA-associated antibiotic. Dissociation constants were measured by NMR spectroscopy for two sites of interaction (K(d1)=150+/-40 microM; K(d2)=360+/-50 microM). Furthermore, the effects of the Cu(II) ion on the antibiotic, on the RNA fragment that mimics the bacterial ribosomal A site, and on the complex formed between these two entities were analyzed. The study led to the proposal of a model that localizes the copper ion within the kanamycin-RNA complex.