The two-step assemblies of basic-amino-acid-rich peptide with a highly charged polyoxometalate

Two-step assembly of a peptide from HPV16 L1 with a highly charged europium-substituted polyoxometalate (POM) cluster, accompanying a great luminescence enhancement of the inorganic polyanions, is reported. The mechanism is discussed in detail by analyzing the thermodynamic parameters from isothermal titration calorimetry (ITC), time-resolved fluorescent and NMR spectra. By comparing the actions of the peptide analogues, a binding process and model are proposed accordingly. The driving forces in each binding step are clarified, and the initial POM aggregation, basic-sequence and hydrophobic C termini of peptide are revealed to contribute essentially to the two-step assembly. The present study demonstrates both a meaningful preparation for bioinorganic materials and a strategy using POMs to modulate the assembly of peptides and even proteins, which could be extended to other proteins and/or viruses by using peptides and POMs with similar properties. Assemble to order: Stepwise assembly of a basic peptide sequence from HPV 16L1 and its analogues induced by a europium-substituted polyoxometalate (K₁₃[Eu(SiW₁₀MoO₃₉)₂]) are reported (see scheme), and the assembly triggered luminescence enhancement and the intrinsic mechanism are discussed.