NMR study of pradimicin derivative BMY-28864 and its interaction with calcium ions in D2O

The dynamic structure of the antifungal antibiotic pradimicin BMY-28864 in D2O and its interaction with calcium ions were analyzed using one- and two- dimensional H-1 nuclear magnetic resonance (NMR). Spectra indicate extensiv e self-association of molecules in the solution. Two-component spectra were observed simultaneously in a very dilute solution, suggesting equilibrium of two aggregative states. The addition of CaCl2 caused a number of changes in NMR spectra. Therefore we concluded that pradimicin BMY-28864 could for m a complex with the Ca2+ ion, causing a movement of the equilibrium. The p osition of the bound calcium ion is determined indirectly by observing how the NMR shift affects protons that are close to the binding site. The stoic hiometry of Ca2+ ion to the Pradimicin molecule for the Ca2+-saturated comp lex is verified to be 1.2. Signal broadening and changes in chemical shift in the H-1 NMR spectroscopy of BMY-28864 are assumed to be related to chang es in the molecular aggregate conformation. (C) 1999 Elsevier Science B.V. All rights reserved.