Two-Channel Bioprotonic Photodetector.

Merging biological systems with electronic components requires converting biological ionic currents into electrical signals. Previously, we coupled green-light-activated transport of protons by a palladium-binding version of deltarhodopsin (HtdR) with electronic signal generation by exploiting palladium hydride (PdHx) formation on palladium (Pd) electrodes. Here, we broaden the scope of these devices by showing that blue proteorhodopsin (BPR) from marine bacteria is a suitable proton pump for expanding their spectral range.

Role of the signal sequence in proteorhodopsin biogenesis in E. coli.

Blue-absorbing proteorhodopsin (BPR) from marine bacteria is a retinal-bound, light-activated, outwards proton transporter containing seven α-helical transmembrane segments (TMS). It is synthesized as a precursor species (pre-BPR) with a predicted N-terminal signal sequence that is cleaved to yield the mature protein. While optimizing the production of BPR in Escherichia coli to facilitate the construction of bioprotonic devices, we observed significant pre-BPR accumulation in the inner membrane and explored signal sequence requirements and export pathway.

Affinity purification of Car9-tagged proteins on silica matrices: Optimization of a rapid and inexpensive protein purification technology.

Car9, a dodecapeptide identified by cell surface display for its ability to bind to the edge of carbonaceous materials, also binds to silica with high affinity. The interaction can be disrupted with l-lysine or l-arginine, enabling a broad range of technological applications. Previously, we reported that C-terminal Car9 extensions support efficient protein purification on underivatized silica.

Electronic control of H current in a bioprotonic device with Gramicidin A and Alamethicin.

In biological systems, intercellular communication is mediated by membrane proteins and ion channels that regulate traffic of ions and small molecules across cell membranes. A bioelectronic device with ion channels that control ionic flow across a supported lipid bilayer (SLB) should therefore be ideal for interfacing with biological systems. Here, we demonstrate a biotic-abiotic bioprotonic device with Pd contacts that regulates proton (H) flow across an SLB incorporating the ion channels Gramicidin A (gA) and Alamethicin (ALM).

A Palladium-Binding Deltarhodopsin for Light-Activated Conversion of Protonic to Electronic Currents.

Fusion of a palladium-binding peptide to an archaeal rhodopsin promotes intimate integration of the lipid-embedded membrane protein with a palladium hydride protonic contact. Devices fabricated with the palladium-binding deltarhodopsin enable light-activated conversion of protonic currents to electronic currents with on/off responses complete in seconds and a nearly tenfold increase in electrical signal relative to those made with the wild-type protein.