Electrochemical characterization of LHCII on graphite electrodes – Potential-dependent photoactivation and arrangement of complexes

The coupled photocycle of phenyl-p-benzoquinone and Light-Harvesting Complex II (LHCII) within the biohybrid system

“…The analyzes showed the presence of Lhcb1, Lhcb2, and Lhcb3 polypeptides and the lack of the D1 and D2 of PSII core subunits (Fig. S1 ), which indicates the high purity of the LHCII samples used according to our previous results 12 .…”

“…S11 ), similarly to room temperature spectra of isolated LHCII 42 . The signal of free Chl at 665 nm was not noted 12 , that confirms retaining of LHCII 3 in its native structure. These observations point to quite unlimited migration of LHCII 3 into GE with concomitant decreasing of surface-density of complexes.…”

“…1 C,D). Although photocurrent was generated in the GE-LHCII system without exogenous redox mediators 12 , the addition of the PPBQ to the reaction buffer caused a 20-fold increase in photocurrent intensity (Fig. S3 A), whereas the release of PPBQ from the reaction vessel decreased this reaction (Fig.…”

“…All electrochemical experiments were carried out using a disposable planar screen-printed three-electrode system composed of a round graphite working electrode (geometric area of 0.07 cm 2 ), an Ag/AgCl pseudo-reference electrode (Ag/AgCl RE), and a graphite counter electrode. The properties of this graphite electrode (GE), as well as the procedure of cleaning and activation of the carbon surface, were described in details previously 12 , 44 . The potential of a pseudo-reference electrode in HEPES buffer (20 mM HEPES, 15 mM NaCl, 4 mM MgCl 2 , pH 7.5) was controlled against the saturated calomel electrode (SCE) and was equal to 0.080 ± 0.005 V. This gives a potential equal to 0.324 ± 0.005 V against a normal hydrogen electrode (NHE).…”

“…We have previously found that the generation of photocurrent by LHCII immobilized within porous graphite electrode (GE) might depend on endogenous PQ molecules, non-specifically bound to complexes 12 . In this report, we verify the operation of a graphite electrode-based biohybrid system, in which we use LHCII 3 as the photoactive layer and PPBQ as the MET reagent.…”