Electrogenic proton transfer in Rhodobacter sphaeroides reaction centers: effect of coenzyme Q₁₀ substitution by decylubiquinone in the Q_B binding site

Abstract

An electrometric technique was used to investigate the effect of coenzyme Q(10) (UQ), substitution by decylubiquinone (dQ) at the Q(B) binding site of reaction centers (UQ-RC and dQ-RC, respectively) on the electrogenic proton transfer kinetics upon Q(B) reduction in Rhodobacter sphaeroides chromatophores. Unlike dQ-RC, the kinetics of the second flash-induced proton uptake in UQ-RC clearly deviated from the mono-exponential one. The activation energy (about 30 kJ/mol) and the pH profile of the kinetics in dQ-RC were similar to those in UQ-RC, with the power law approximation used in the latter case. The interpretation of the data presumed the quinone translocation between the two binding positions within the Q(B) site. It is proposed that the native isoprenyl side chain (in contrast to decyl chain) favors the equilibrium binding of neutral quinone at the redox-active 'proximal' position, but causes a higher barrier for the hydroquinone movement from 'proximal' to 'distal' position.

Design and modelling of a photo-electrochemical transduction system based on solubilized photosynthetic reaction centres

“…It is clear that dQ outperforms all tested electron acceptors, presenting the best compromise between water solubility and Q B site affinity. A further factor in agreement with the high performances of dQ in sustaining the electron flow within our PEC is the intrinsic rate of the quinol release from the Q B site, which has been found higher for dQ than UQ 10 [45]. This finding has been rationalized with the enhanced flexibility of the saturated…”

“…decyl side chain of dQ whit respect to the isoprenoid one of UQ 10 , allowing faster movements of the former once reduced [45]. Fig.…”

Highly oriented photosynthetic reaction centers generate a proton gradient in synthetic protocells

“…S2C). In fact, dQ is a ubiquinone analogous that binds to the RC Q B -site and accepts electrons as well (56). When added to RC@GUVs suspension, it is expected that dQ will insert into the lipid membrane and diffuse and bind to RC Q B -site.…”

A comparative evaluation of coenzyme Q10-loaded liposomes and solid lipid nanoparticles as dermal antioxidant carriers

“…17 A decrement in the liposome dimension might be due to the shrinkage of the aqueous volume of the vesicle resulting in smaller dimensions by the addition of Q10, which is a very lipophilic substance (logP .. 10). 18 This phenomenon could be explained by either the osmotic effect or the membrane folding. Since the total area of the membrane of each liposome was maintained, the folding of the membrane might cause this size reduction.…”