dlvr.it
Let’s Get Cyclic – Influence of Head-to-Tail Cyclisation of Lanmodulin-inspired peptides on Lanthanide Affinity and Structure
Over the recent years lanthanide-binding proteins such as lanmodulin, a naturally lanthanide-binding EF-hand protein from Methylorubrum extorquens AM1, as well as protein-inspired lanthanide-binding peptides have become of increasing interest for the development of separation and recycling methods for rare earth elements. For the first time, a set of head-to-tail cyclised lanmodulin-inspired peptides and their complexation behaviour towards lanthanides was comprehensively examined in aqueous media using time-resolved laser induced fluorescence spectroscopy (TRLFS), isothermal titration calorimetry (ITC), nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopies, complemented by molecular dynamic (MD) simulations and advanced mass spectrometry methods. Results obtained from this multi-method approach evidence that the head-to-tail cyclisation can indeed increase the lanthanide-affinity in natural sequences and positively impact the pre-organisation of the metal-free peptide while limiting the amount of formed complex species in comparison to linear analogues. Furthermore, the impact of minimal sequence alterations by inserting glycine is shown to be useful in NMR experiments for probing alterations in the local environment of neighbouring amino acids potentially involved in coordination. Lastly, KD values for the peptides with the whole Ln series (except Pm) and the actinide curium are presented.
