Molecular interaction between europium decatungstate and histone H1 and its application as a novel biological labeling agent.

Polyoxometalates (POMs) show promising biological activities, but the mechanism of potential therapeutic effects remains to be elucidated at a molecular level. As a step toward the elucidation of the mechanistic pathways governing the bioactivity of POMs, the interaction between Eu-containing decatungstate [EuW10O36]9- (EuW10) and histone H1 has been studied. Fluorescence/luminescence analysis showed the existence of a strong interaction between EuW10 and histone H1. This interaction has key effects both on the luminescence of EuW10 and on the structure of histone H1. A gradual and intense enhancement of EuW10 luminescence was observed upon addition of increasing concentrations of histone H1. Circular dichroism investigations indicated that the binding of EuW10 significantly alters the secondary structure of histone H1. The present work is meaningful in finding novel labeling agents for fluorescence/luminescence or solid-state bioimaging.