The Interplay of Conjugation and Metal Coordination in Tuning the Electron Transfer Abilities of NTA-Graphene Based Interfaces

An artificial leaf is a concept that not only replicates the processes taking place during natural photosynthesis but also provides a source of clean, renewable energy. One important part of such a device are molecules that stabilize the connection between the bioactive side and the electrode, as well as tune the electron transfer between them. In particular, nitrilotriacetic acid (NTA) derivatives used to form a self-assembly monolayer chemisorbed on a graphene monolayer can be seen as a prototypical interface that can be tuned to optimize the electron transfer. In the following work, interfaces with modifications of the metal nature, backbone saturation, and surface coverage density are presented by means of theoretical calculations. Effects of the type of the metal and the surface coverage density on the electronic properties are found to be key to tuning the electron transfer, while only a minor influence of backbone saturation is present. For all of the studied interfaces, the charge transfer flow goes from graphene to the SAM. We suggest that, in light of the strength of electron transfer, Co2+ should be considered as the preferred metal center for efficient charge transfer.

Heterologous Expression of Pediocin/Papa in Bacillus Subtilis

Listeria moniocytogenes is food-borne pathogen. Pediocin is group II α bacteriocin with anti-listeria activity, naturally produced by Pediococuus acidilactic and Lactobacillus plantarum. Gene pepA/papA encode for pediocin. Expression and secretion of active papA was relayed on transporter papC and accessary protein papD on the same operon in native host. The excretion machines were also necessary for pediocin protein expression in heterologous host of E. coli, Lactobacillus lactis, and Corynebacterium glutamicum. In this study, two vector carrying codon sequence of papA mature peptide was constructed, with or without His tag. Both fragments were inserted into plasmid pHT43 and transformed Bacillus subtilis WB800N. The strains were induced with IPTG to secrete recombination protein PA1 and PA2 respectively. Supernatant from both recombination strains can inhibit Listeria monocytogenes ATCC54003 directly. The fused protein possesses inhibition activity as a whole, exempting from cleavage of leading peptide. Protein PA1 can be purified by nickel-nitrilotriacetic acid (Ni-NTA) metal affinity chromatography. This is the first report for active pediocin expression without assistance of papCD in heterogenous host.