Association of Keplerate-Type Polyoxometalate {Mo72Fe30} with Tetracycline: Nature of Binding Sites and Antimicrobial Action

The association process between the tetracycline (TC) antibiotic molecule and Keplerate-type nanocluster polyoxometalate (POM) {Mo72Fe30} was studied in aqueous solution. The novel supramolecular ensemble {Mo72Fe30}@TC12.5 was produced, its composition and structure were revealed by means of elemental analysis (C, N, H) and vibrational spectroscopy (IR and Raman). Based on the spectral data, the POM structure’s integrity was confirmed and binding sites of TC with the Keplerate {Mo72Fe30} surface were found. Due to thermogravimetric analysis (TG) and in-situ Raman spectroscopy during the process of {Mo72Fe30}@TC12.5 thermal destruction, we showed a significant change in the phase composition of POM’s destruction products after association with TC. The antibacterial activity of the obtained complex {Mo72Fe30}@TC12.5 was examined. The experimental results allowed us to note the partial inhibition of TC’s antibacterial activity owing to the coordination of TC to FeIII centers, in turn, which hinders the participation of TC in coordination via Mg2+ of ribosomal subunits 30S in bacteria.