Highly simplified de novo designed proteins, maquettes, offer new opportunities for the design of catalytic or photochemically active, electrochemically regulated, bioinspired nanomaterials. To achieve efficient charge separation for energy generation and storage, we have extended work done with overall hydrophilic (HP) a-helical bundles and developed a new amphiphilic (AP) maquette family that assembles within membranes and at interfaces. The AP design introduced new lipophilic (LP) domains that are covalently linked to the original HP maquettes or their derivatives. The AP maquettes were fabricated with cofactor ligating site within both the HP and LP domains. Notably, the maquettes with cofactor binding site within the LP domain enable binding of larger variety of hydrophobic cofactors including Ni- and Zn-bacteriochlorophylls (Bchls) and thereby expand the functional versatility. The Ni-BChl is especially useful as a reporter of the local coordination state (see Figure) whereas the Zn-BChl provides sufficiently long excited state lifetimes to efficiently initiate photoinduced electron transfer.
Figure: Newly designed AP family maquettes bind metal-substituted analogs of bacteriochlorophylls such as Zn-BChl and Ni-BChl (left). The absorption spectra on the right illustrate the remarkable color changes of Ni-BChl that correlate with the type and number of axial ligands: the purple spectrum represents 4-coordinated Ni-BChl, the green represents 5-coordinated Ni-BChl-imidazol, and the blue 6-coordinated Ni-BChl bound to AP3 maquette.