Trapping of a long-living charge separated state of photosynthetic reaction centers in proteoliposomes of negatively charged phospholipids

Agostiano, Angela; Milano, Francesco; Trotta, Massimo

doi:10.1007/s11120-004-3197-6

Cited by 13 publications

(8 citation statements)

References 37 publications

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“…The relative weight of these slower phenomena is artificially increased when the experimental setups have a lower collection rate than the fast component of the recombination time. [36] For LEGOT characterization, transfer characteristics have been acquired continuously. During acquisition, the light excitation source has been switched ON and OFF every 200 s. The time evolution of transfer characteristics is reported in Figure 3.B and Figure 3.C for TIPS-P5 and PEDOT:PSS devices, respectively.…”

Section: Legotmentioning

confidence: 99%

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A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light

Lauro

Gatta

Bortolotti

et al. 2019

Adv Elect Materials

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The photochemical core of every photosynthetic apparatus is the reaction center, a transmembrane enzyme that converts photons into charge-separated states across the biological membrane with an almost unitary quantum yield. We present a light-driven organic transistor architecture, which converts light into electrical current by exploiting the efficiency of this biological machinery. Proper surface tailoring enables the integration of the bacterial reaction center as photoactive element in organic transistors, allowing the transduction of its photogenerated voltage into photomodulation of the output current up to two orders of magnitude. The device architecture, termed Light-driven Electrolyte-Gated Organic Transistor (LEGOT), is the prototype of a new generation of low-power hybrid bio-optoelectronic organic devices. Main text Evolution has engineered multi-protein complexes to efficiently convert solar radiation into chemical energy, [1] sustaining the energy needs of life on planet Earth via the photosynthetic process. These photoenzymes catalyze the uphill conversion of oxidized molecules to their reduced forms, using light as energy source. Photosynthetic organisms, such as plants, algae, and some bacteria are the sole kind of organisms on the planet able to harvest and store energy. [2] The photosynthetic anoxygenic bacteria possess a photosynthetic apparatus based on a single functional unit, the reaction center (RC), which converts photons into charge-separated states across the membrane with unmatched quantum yield. Rhodobacter (R.) sphaeroides is a purple non-sulphur bacterium, whose RC is a three-subunit transmembrane protein sitting within the photosynthetic membrane. [3] Light impinges a cascade of electron transfer reactions that forms the hole-electron couple with a unitary quantum yield. [4] In absence of exogenous electron donors and acceptors, this state does not evolve further and has a lifetime ranging from hundred milliseconds up to three seconds. [5] See Figure S1 in the Supporting Information.

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Section: Legotmentioning

confidence: 99%

“…This is due to the accumulation, induced by continuous illumination, of usually negligible transient species in the RC having much longer lifetime. The relative weight of these slower phenomena is artificially increased when the experimental setups have a lower collection rate than the fast component of the recombination time …”

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confidence: 99%

A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light

Lauro

Gatta

Bortolotti

et al. 2019

Adv Elect Materials

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“…also inset of Figure 5) leading to an increment of the RC population with reconstituted Q B site (as measured by the increased contribution of the slow phase charge recombination) (Agostiano et al 2005). Since Q B -is a strongly bound quinol form, it is very difficult for terbutryn to compete for the binding site with this species.…”

Section: Discussionmentioning

confidence: 96%

Structure and binding efficiency relations of QB site inhibitors of photosynthetic reaction centres*

Husu

Magyar²,

Szabó³

et al. 2015

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Abstract. Many herbicides employed in agriculture and also some antibiotics bind to a specific site of the reaction centre protein (RC) blocking the photosynthetic electron transport. Crystal structures showed that all these compounds bind at the secondary ubiquinone (Q B ) site albeit to slightly different places. Different herbicide molecules have different binding affinities (evaluated as inhibition constants, K I , and binding enthalpy values, ∆H bind ). The action of inhibitors depends on the following parameters: (i) herbicide molecular structure; (ii) interactions between herbicide and quinone binding site; (iii) protein environment. In our investigations K I and ∆H bind were determined for several inhibitors. Bound herbicide structures were optimized and their intramolecular charge distributions were calculated. Experimental and calculated data were compared to those available from databank crystal structures. We can state that the herbicide inhibition efficiency depends on steric and electronic factors, i.e. geometry of binding with the protein and molecular charge distribution, respectively. Apolar bulky groups on N-7 atom of the inhibitor molecule (like t-buthyl in terbutryn) are preferable for establishing stronger interactions with Q B site, while such substituents are not recommended on N-8. The N-4,7,8 nitrogen atoms maintain a larger electron density so that more effective H-bonds are formed between the inhibitor and the surrounding amino acids of the protein.

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“…LRO-incorporating liposomes were prepared using the MVT method as reported in ref. 31 with some modications, that will be referred as method A. Briey, an aliquot of LRO (2-20 mg) was weighted and mixed to a suitable volume of POPC ethanol solution (40 mg mL À1 ) in order to reach mass ratios LRO/POPC ranging from 0.1 to 10, roughly corresponding to lycopene/ POPC molar ratios between 1 : 700 and 1 : 7 respectively. Added ethanol proved to solubilize only partially oleoresinassociated carotenoids, leading to a dark-reddish residue of undispersed material.…”

Section: Liposome Preparationmentioning

confidence: 99%

Lipid/detergent mixed micelles as a tool for transferring antioxidant power from hydrophobic natural extracts into bio-deliverable liposome carriers: the case of lycopene rich oleoresins

et al. 2015

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This work demonstrates that lipid-detergent mixed micelles can be employed successfully in order to achieve and modulate the transfer of bio-active hydrophobic compounds into lipid carriers by means of a simple and bio-safe procedure. In our specific investigation, liposome preparations incorporating mixtures of natural carotenoids with high lycopene content were developed and characterized, aiming to obtain formulations of potential nutraceutical and pharmaceutical interest. The starting material was a solvent-free high-quality lycopene rich oleoresin (LRO) obtained by extracting a freeze-dried tomato matrix with supercritical carbon dioxide (SC-CO 2 ). Mixed micelles containing 1-palmitoyl-2-oleoyl-snglycero-3-phosphocholine (POPC) and cholate were loaded with LRO antioxidants by means of two slightly different procedures, which surprisingly resulted in significant differences in both quality and quantity of incorporated carotenoids. In particular, the selective incorporation of (all-E)-lycopene was achieved by extracting the oleoresin with a pre-formed cholate/POPC micelle suspension whilst (Z)-isomers were preferentially integrated when treating a POPC/LRO mixed film with cholate. The micelle to vesicle transition (MVT) method was employed in order to produce vesicles of well-defined lamellarity and size. Visible and infrared (IR) spectroscopy as well as Dynamic Light Scattering (DLS) andTransmission Electron Microscopy (TEM) measurements allowed the extensive characterization of LRO-loaded micelles and liposomes. The antioxidant potential of preparations was assessed by measuring the radical scavenging activity towards the coloured radical cation of 2,2 0 -azinobis(3-ethylbenzothiazoline-6-sulphonate) (ABTS). Important information about the reliability of different approaches for antioxidant capacity evaluation of micelle and liposome preparations was gained and the successful incorporation of LRO antioxidant power in a bio-deliverable water-dispersed form was demonstrated.

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Trapping of a long-living charge separated state of photosynthetic reaction centers in proteoliposomes of negatively charged phospholipids

Cited by 13 publications

References 37 publications

A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light

A Bacterial Photosynthetic Enzymatic Unit Modulating Organic Transistors with Light

Structure and binding efficiency relations of QB site inhibitors of photosynthetic reaction centres*

Lipid/detergent mixed micelles as a tool for transferring antioxidant power from hydrophobic natural extracts into bio-deliverable liposome carriers: the case of lycopene rich oleoresins

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