The initial task of our project was to develop de novo designed CC peptides as novel ligands for metal ions to generate a new class of protein-based inorganic complexes. Taking advantage of peptide design principles, O-donor ligands (Asparagine and Aspartate residues) were introduced into a library of parallel three stranded CCs. These were synthesized, purified and characterized. We then explored their binding capability with a range of metals including Sc3+, VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+ and Y3+ and lanthanides (La3+, Gd3+ and Tb3+) and interrogated their coordination chemistry. We have attempted to use some of the lanthanide CC as catalysts for phosphate hydrolysis and Aldol reactions. But the yield of the reaction products was lower than that for the control experiments with Ln3+ alone.
Furthermore, we have used 139La NMR as a tool to probe the dynamic nature and coordination chemistry of CCs upon binding with a La3+ ion. The line width of the 139La NMR signal helped us to ascertain the exchange rate of La3+ between the free and protein-bound states, which we believe may be contributing to their poor catalytic performance.
MCCs were also probed by double electron-electron resonance (DEER) spectroscopy, as this can selectively detect the paramagnetic species and ignore the diamagnetic background. In particular, site-directed spin labeling of a protein moiety combined with DEER spectroscopy has emerged as a powerful tool to investigate the structural and the dynamical aspects of biomolecules. In view of the above, we have developed a series of spin-labeled CCs and employed DEER for measuring distances between the spin label and paramagnetic metal centers Cu2+ or Gd3+.
As a result of this work, seven posters in the field of MCC peptides were presented in the following national and the international conference meetings.
ISABC2017: 14th International Symposium on Applied Bioinorganic Chemistry, 7-10 Jun 2017 Toulouse, France. Title: “La3+ binding to a series of de novo designed coiled coils-probed by 139La-NMR”; Postgraduate Symposium on Nanoscience and Nanotechnology, December 13th 2016, Title: “Binding of first row transition metals to a de novo designed coiled coil peptide”; Postdoctoral / Early Researcher, Career Development and Training (PERCAT) Gala Conference, October 27th 2016, Title: “Copper(II) and Zinc(II) selective binding de novo designed coiled coil peptide”; Engineering and Physical Sciences (EPS) Research Conference (internal event), October 25th 2016, University of Birmingham (UOB), Birmingham, UK. Title: “Copper(II) interacting de novo designed coiled coil peptide”; 13th European Biological Inorganic Chemistry Conference (EUROBIC-13), August 29th to September 1st, 2016, Budapest, Hungary. Title: “Binding of first-row transition metals to a de novo designed coiled coil peptide is consistent with the Irving William series”; Marie Skłodowska-Curie Actions Conference ESOF Satellite Event ‘Research and Society’ (MSCA ESOF-2016), July 28th to 29th 2016, The University of Manchester, Manchester, UK. Title: “De novo designed first row transition metal coiled coils”; The Dalton 2016 meeting (DALTON-2016), March 29th to 31st 2016, University of Warwick, Coventry, UK. Title: “De novo designed lanthanide coiled coils as catalysts in phosphodiester hydrolysis reaction in aqueous medium”.
