Location of ubiquinone homologues in liposome membranes studied by fluorescence anisotropy of diphenyl-hexatriene and trimethylammonium-diphenyl-hexatriene

Journal of Colloid and Interface Science

2012

Ubiquinone and plastoquinone are two of the main electron and proton shuttle molecules in biological systems, and monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in the thylakoid membrane of chloroplasts. Saturated MGDG, ubiquinone-10 (UQ) and MGDG:UQ mixed monolayers at the air/water interface have been studied using Surface Pressure-Area isotherms and Brewster Angle Microscopy. Moreover, the transferred Langmuir-Blodgett films have been observed by Atomic Force Microscopy. The results show that MGDG:UQ mixtures present more fluid phase than pure MGDG indicating a higher order degree for the later. It is also observed an important influence of UQ on the MGDG matrix before UQ collapse pressure and a low influence after this event, due to UQ expulsion from the MGDG matrix. This expulsion leads to a similar remaining UQ content for all the tested mixtures, indicating a limiting content of this molecule in the MGDG matrix at high surface pressures. The thermodynamic studies confirm the stability of the MGDG:UQ mixtures at low surface pressures, although presenting a non-ideal behaviour. Results point to consider UQ as a good candidate for studies of artificial photosynthesis.

“…5 Chloroform of analytical grade was used in solutions preparation, and water was ultrapure MilliQ® (18.2 M ·cm). Mica sheets were purchased from TED PELLA Inc (CA).…”

Section: Methodsmentioning

confidence: 99%

“…On the other hand, ubiquinone, UQ, is present in eukaryotic cells at the hydrophobic core of the phospholipid bilayer of the inner membrane of mitochondria, where plays the role of electron and proton shuttle [4,5,6].…”

Section: Introductionmentioning

confidence: 99%

Biomimetic monolayer films of monogalactosyldiacylglycerol incorporating ubiquinone

Journal of Colloid and Interface Science

2012

“…The different shape of reduction and oxidation peaks can be explained by the different hydrophilic character of the redox couple UQ/UQH2. The larger polarity of UQH2 compared with UQ leads the former to establish better attractive interactions by dipole-dipole or hydrogen bond between UQH2 and MGDG headgroups and, in addition, the UQH2-ITO, UQH2-UQH2 and UQH2-water interactions are also enhanced [2,30,39,42]). During the oxidation scan UQH2 is the reactant so the possibilities of hydrogen bonds are larger, increasing the stabilization of the UQH2 molecule and making it more difficult to oxidise.…”

Section: Electrochemical Response Of the Mgdg:uq-ito/electrolyte Systemmentioning

confidence: 99%

“…On the other hand, quinones are redox molecules that act as electron and proton shuttles in natural electron transfer processes. Ubiquinones, UQs, especially UQ-10, are involved in the respiratory chain whereas plastoquinones, PQs, especially PQ-9, are involved in the photosynthetic chain [1,2]. Some attempts have been done to simulate artificial photosynthesis using others quinones than PQ-9 [3][4][5], being UQ-10 one natural candidate because it is structurally close to PQ-9 and its obtaining cost is quite lower.…”

Section: Introductionmentioning

confidence: 99%

Electrochemistry of LB films of mixed MGDG:UQ on ITO

et al. 2015

Bioelectrochemistry

. C/ Colom 1, 08222 Terrassa (Barcelona), Spain. Tl: 34 937398043. AbstractThe electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being kRapp(I)= 2.2·10 -5 s , respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positons are known as diving and swimming.

“…Focusing the attention in bioenergetics processes, ubiquinone-10 (UQ) and plastoquinone-9 are known to be an important kind of natural quinones involved in the respiratory and photosynthetic pathways of the mitochondrial and thylakoid membranes, respectively [1][2][3]. In particular, the UQ molecule contains a quinone redox centre (head) and a long isoprenoid chain (tail) of ten isoprenoid units (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Electrochemical behaviour of mixed LB films of ubiquinone – DPPC

Journal of Electroanalytical Chemistry

et al. 2012

The structure and the electrochemical behaviour of Langmuir and Langmuir-Blodgett (LB) films of the biological ubiquinone-10 (UQ) and a mixture of dipalmytoilphosphatidylcholine (DPPC) and UQ at the molar ratios DPPC:UQ 5:1 and 10:1 have been investigated. The surface pressure-area isotherms of the Langmuir films and the AFM images of the LB films show the formation of a monolayer in the DPPC:UQ mixture till a certain surface pressure is attained, and then at higher surface pressures the UQ is progressively expelled. The cyclic voltammograms of DPPC:UQ LB films formed on indium tin oxide, ITO, at different surface pressures show one reduction and one oxidation peak at low surface pressures, but two or even more reduction and oxidations peaks at medium and high surface pressures. The electrochemical behaviour is correlated with the film structure.