BSA binding and antimicrobial studies of branched polyethyleneimine–copper(II)bipyridine/phenanthroline complexes

The interaction of two water soluble branched polyethyleneimine–copper(II) complexes containing bipyridine/phenanthroline with bovine serum albumin (BSA) was studied by, UV–Visible absorption, fluorescence, lifetime measurements and circular dichroism spectroscopic techniques. The polymer–copper(II) complexes strongly quench the intrinsic fluorescence of BSA is the static quenching mechanism through hydrogen bonds and van der Waal’s attraction. The distance r, between the BSA and the complexes seems to be less than 2 nm indicating that the energy transfer between the donor and acceptor occurs with high probability. Synchronous fluorescence studies indicate the binding of polymer–copper(II) complexes with BSA mostly changes the polarity around tryptophan residues rather than tyrosine residues. The circular dichroism studies indicate that the binding has induced considerable amount of conformational changes in the protein. The complexes also show some antibacterial and antifungal properties.

Graphical abstractThe binding constant for the binding between polymer–copper(II) complex and BSA depend on the degree of coordination (x) of the copper complex units in the polymer back bone chain.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Binding of some polymer–copper(II) complexes with bovine serum albumin. ► Hydrogen bonding attraction plays a major role in the binding process. ► Binding induces considerable amount of conformational changes in the protein. ► These polymer–copper(II) complexes show anti bacterial and antifungal activities.