Objective: To study the transport activity of bacterial rhodopsins, proteoliposomes with the same orientation of the protein molecules should be obtained. Methods: The genes of fusion proteins containing Exiguobacterium sibiricum proteorhodopsin (ESR) and various N-terminal soluble domains have been constructed. Results and Discussion: Effective synthesis in Escherichia coli cells was observed only in the case of fusion with chaperone Caf1M and maltose-binding protein MBP expressed as precursors with their own signal sequences. The study of the isolated MBP-ESR protein in micelles and proteoliposomes demonstrated formation and decay of the main photocycle intermediates at pH > 8. The photoelectric response of the fusion proteins Caf-ESR and MBP-ESR is comparable in amplitude to the wild-type ESR response, indicating their homogeneous orientation in the proteoliposome membrane. Conclusions: The obtained constructs can be used to create bacterial expression systems for various retinal proteins, ensuring their uniform incorporation into proteoliposomes.

The genes of hybrid proteins including Exiguobacterium sibiricum proteorhodopsin (ESR) and various N-terminal soluble domains have been constructed. Effective synthesis in Escherichia coli cells was observed only in the case of hybrids with chaperone Caf1M and maltose-binding protein MBP expressed as precursors with their own signal sequences. The study of the isolated MBP-ESR protein in micelles and proteoliposomes demonstrated formation and decay of the main photocycle intermediates at pH 8. The photoelectric response of the hybrid proteins Caf-ESR and MBP-ESR is comparable in amplitude to the wild-type ESR response, indicating their homogeneous orientation in the membrane. The obtained constructions can be used to create bacterial expression systems for various retinal proteins, ensuring their uniform incorporation into proteoliposomes.

The effect of cationic antiseptics (at micromolar concentrations) on PSII active core complexes isolated from spinach plants with an intact water oxidation complex and on PSI core complexes from cyanobacterium Synechocystis sp. PCC6803 were studied. Of the antiseptics studied (miramistin, chlorhexidine, octenidine, and picloxydine), octenidine had the greatest effect. It was concluded that its effect on PSII consisted primarily in affecting the structure of the light-harvesting antenna (CP43 and CP47), through which the excitation energy is delivered to the reaction center. As a result, the chlorophyll molecules in this structure were destabilized and their optical and functional characteristics changed. Similar effects were also observed in cyanobacterial complexes of PSI. In addition, the antiseptic affected the rate of establishment of the equilibrium distribution of excited states by spectral forms in the PSI antenna complex. A significant effect of octenidine on the electron transfer rate in the PS I complex was also found: in its presence, the recombination of photo-separated charges between the photoactive pigment P700 and the terminal acceptor FA/FB occurred twice as fast.

Increasing volumes of produced antiseptics and disinfectants, which are widely used in medicine, veterinary medicine, the food industry and everyday life, can create a serious environmental problem after use. Previously, under the infl uence of micromolar concentrations of a number of antiseptics, we identifi ed disturbances in the functioning of photosynthetic membranes and phototransforming pigment-protein complexes isolated from them in various representatives of photosynthetic organisms. In this work, to determine the sensitivity of photosynthetic membranes to the action of the cationic antiseptic octenidine, we used chromatophores of the purple nonsulfur bacteria Rhodobacter sphaeroides, labeled with the fluorescent dye 10-N-nonylacridine orange (NAO). It was shown that the binding of NAO to chromatophores is accompanied by a shift in the dye emission maximum from 525 to 640 nm. The “red” fluorescence of NAO associated with chromatophores turned out to be sensitive to the effect of increasing concentrations of octenidine on photosynthetic membranes. We have found antiseptic concentrations which led to the degradation of chromatophore structures and change in the NAO aggregative state. It can be detected by an increase of “green” fluorescence in the emission spectra of the dye. The properties of NAO as a fluorescent indicator of the functional state of photosynthetic membranes and possible changes that can occur in such systems under the influence of a cationic antiseptic are discussed.

Carbon dots are a new type of carbon-based material with some unique properties which are attractive for agricultural, biological, medical and nanotechnological applications. The widespread production of graphene for composite materials as well as the formation of carbon dots as by-products (industry, food heat treatment etc.) leading to inevitable environmental pollution. However, the environmental impact posed by them on living organisms is still insufficient investigated. We studied the effects of carbon dots synthesized in our laboratory via electrochemical (classified as graphene quantum dots), hydrothermal and microwave (classified as carbon nanodots) methods on the green microalga Scenedesmus quadricauda. The microalgae were exposed to different concentrations of carbon dots for 6 days. Our results showed that carbon dots did not induce oxidative stress and affect the photosynthetic activity of microalgae. However, carbon dots could decrease the growth rate of microalgae mainly due to reducing light, which occurred via the shading of microalgae by nanoparticles. The obtained results contribute to the understanding of the interaction of carbon dots and microalgae.

We obtain carbon nanoparticles by the electrolysis of sodium hydroxide solution in 94% ethanol on platinum electrodes. Centrifugation, column chromatography, and dialysis are used to isolate and purify nanoparticles from synthesis by-products. The nanoparticles have a hydrodynamic diameter of approximately 14 nm, and their surface potential is –20 mV. The particles are soluble in water due to the hydroxyl and carboxyl groups on their surface and exhibit luminescence in the blue and orange regions of the visible spectrum. The paper discusses the details of the electrochemical synthesis of nanoparticles of this type.

— We have developed an alternative method for the synthesis of an analog of natural retinal, which contains the p -fluorophenyl fragment instead of the trimethylcyclohexene ring. The proposed scheme for the synthesis of the target all-E -isomer of the target retinoid consists of using C 5 -phosphonate that contains the terminal nitrile group under Horner–Emmons reaction conditions. It has been shown that this scheme is more efficient and provides a higher total yield of the target product than the previously described variant. The procedure has been developed for the preparation of an analog of microbial proteorhodopsin ESRh from Exiguobacterium sibiricum , which contains a modified chromophore. It has been found that, as in the case of bacterioopsin from Halobacterium salinarum , the replacement of the trimethylcyclohexene ring in the natural chromophore by the p -fluorophenyl fragment does not prevent the formation of the artificial pigment F-Phe-ESRh from proteorhodopsin ESRh, which preserves the cycle of photochemical reactions. Certain differences have been found between the properties of native recombinant ESRh and its analog F-Phe-ESRh including a shift in the absorption maximum to the short-wavelength region, the formation of M intermediate at lower pH values, the presence of “long-lived M,” and a general slowdown in the photocycle. The reduced stability of the resulting proteorhodopsin analog F-Phe-ESRh to prolonged exposure to visible light has been also demonstrated.

On p. 679 in the list of authors and affiliations instead of: 1 Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127726 Moscow, Russia 2 Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, 119071 Moscow, Russia 3 Institute of Fundamental Problems of Biology of the Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia 4 Kovalevski Institute of Biology of the Southern Seas, Russian Academy of Sciences, 299011 Sevastopol, Russia 5 Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia Should read: 1 Timiryazev Institute of Plant Physiology, Russian Academy of Sciences, 127726 Moscow, Russia 2 Kovalevski Institute of Biology of the Southern Seas, Russian Academy of Sciences, 299011 Sevastopol, Russia 3 Institute of Fundamental Problems of Biology of the Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia 4 Bach Institute of Biochemistry, Research Center of Biotechnology, Russian Academy of Sciences, 119071 Moscow, Russia 5 Lomonosov Moscow State University, Faculty of Biology, 119991 Moscow, Russia

Interaction between upconverting nanoparticles and aluminum octacarboxyphthalocyanine was studied. The efficiency of non-radiative energy transfer from the nanoparticles to phthalocyanine increased with the number of phthalocyanine molecules adsorbed on the nanoparticle, but only up to a certain limit. Further increase in the phthalocyanine concentration resulted in a decrease of its sensitized fluorescence due to the dimerization of dye molecules on the nanoparticle surface. When subjected to infrared irradiation, phthalocyanine molecules in the hybrid complex generated singlet oxygen. The observed effects are of interest in regard to the targeted search for new components of efficient third-generation hybrid photosensitizers.

The temperature dependence of the efficiency of energy migration from the CdSe/CdS/ZnS quantum dots (QDs) with a fluorescence maximum at 580 nm to the reaction centers (RCs) of the bacteria Rb. sphaeroides is practically constant over the temperature range from 100 to ~230–240 K but then decreases 2.5–3 times as temperature further increases to 310 K. The analysis on this dependence on the basis of Förster’s theory showed that the major changes in the energy transfer efficiency are associated with the temperature change in the quantum yield of QD fluorescence, which is due to the activation of intramolecular mobility in the RC structure.

The effect of electrostatic interaction and covalent binding on the energy transfer from negatively charged CdSe/CdS/ZnS-COО− and positively charged CdSe/CdS/ZnS-N H3+ quantum dots to reaction centers of Rb. sphaeroides bacteria (RC) in aqueous solutions is reported. The study was performed using optical absorption and steady-state and time resolved luminescence spectroscopies. The experiments were accompanied by theoretic modelling of charge distribution on the RC surface. More effective energy transfer from positively charged QD to RC, as compared with negatively charged QD, was observed. This effect was associated with the different localization of positively and negatively charged QD on the RC surface. The theoretic analysis has demonstrated that the periplasmic RC side is characterized by larger negative charge density as compared with the cytoplasmic side. Therefore, positively charged QD are localized mainly on periplasmic RC side while negatively charged QD are localized on the cytoplasmic RC side. In RC energy acceptors (porphyrins) are localized closer to the periplasmic side. Therefore, the energy transfer efficiency from positively charged QD is higher. The increase in ionic strength equalizes the charge distribution on both RC sides, thus levelling affinity of differently charged QD with RC. Equal energy transfer efficiency for both covalently bound and unbound QD is due to the fact of QD localization on the same RC side. This study demonstrates that for binding of charged QD with RC the electrostatic interaction is principal.

Fusion with an albumin‐binding domain (ABD) of streptococcal protein G represents a popular approach for half‐life extension of small protein therapeutics in the organism. To increase the circulation time of engineered αvβ3‐integrin‐binding protein (JCL) based on the 10th human fibronectin type III domain ( 10 Fn3), we have constructed several fusions with ABD with different orientations of the partner proteins and linker length. The recombinant proteins were expressed in Escherichia coli cells and purified by nickel‐affinity chromatography. All fusion proteins bound human serum albumin (HSA) in ELISA assay; however, fusions with longer linkers demonstrated better performance. Interaction of ABD‐L 15 ‐JCL and JCL‐L 14 ‐ABD with HSA was confirmed by analytical size exclusion chromatography and pull‐down assays. Surprisingly, the thermal stability of ABD‐L 15 ‐JCL was dramatically decreased in comparison with JCL and JCL‐L 14 ‐ABD proteins. Pharmacokinetic studies revealed that JCL‐L 14 ‐ABD circulated in murine blood about 10 times longer than ABD‐L 15 ‐JCL and 960 times longer than JCL. Biodistribution studies of JCL‐L 14 ‐ABD in mice revealed its increased level in blood and a decreased accumulation in liver and kidneys in comparison with JCL. Obtained results demonstrate the utility of the fusion with ABD for half‐life extension of the binding proteins based on 10 Fn3.

In this work, we have studied the interaction between upconversion nanoparticles, and aluminum octacarboxyphthalocyanine in water solutions. It was shown that the self-assembled hybrid complexes are stable in water and NaCl solutions. The efficiency of nonradiative energy transfer from nanoparticles to the aluminum phthalocyanines increases with the number of phthalocyanine molecules in solution, but phthalocyanine sensitized fluorescence decreases due to phthalocyanine dimerization process. Also, singlet oxygen was generated by the phthalocyanine in the hybrid complex under infrared laser irradiation. The detected effects are of interest from the point of view of the directional search of components for a hybrid, highly efficient photosensitizers.

The temperature dependence of the dark recombination rate in photooxidized bacteriochlorophyll (P) and photoreduced quinone acceptors (ubiquinones) Q(A) and Q(B) of photosynthetic reaction centers of purple bacteria Rhodobacter sphaeroides (Rb. sphaeroides) was studied. Photoinduced changes in the absorption were detected in the Q. absorption band of photooxidized bacteriochlorophyll at 600 nm and in the bands corresponding to the redox changes of ubiquinones at 335 and 420-450 nm. Kinetic analysis was used to evaluate the activation energy and the characteristic time of the transient process of relaxation accompanying electron stabilization at the final quinone acceptor. A comparative study of the kinetics of oxidation-reduction reactions of photoactive bacteriochlorophyll RC purple bacteria and quinone acceptors in their individual absorption bands is an informative approach to studying the mechanisms of this stabilization. The analysis of the revealed kinetic differences makes it possible to estimate the activation energy and the characteristic times of the transition relaxation processes associated with the stabilization of the electron in the quinone acceptor part of RC. Purple bacterial reaction centers have fundamental similarities with PSII reaction centers. Such a similarity represents evolutional closeness between the two types of RC. So it is possible that the photoinduced charge separation in PSII RC, as well as in purple bacteria RC, is also accompanied by definite conformational changes. The possible role of hydrogen bonds of surrounding protein in the relaxation processes accompanying the electron transfer to quinone acceptors is discussed.

The temperature dependence of the efficiency of energy transfer from polymer coated CdSe/CdS/ZnS quantum dots bearing terminal carboxyl groups to the reaction centers of purple bacteria Rb. sphaeroides was investigated experimentally. It was established that this efficiency remained almost constant with the change of temperature from 100 to approximately 230 K, but decreased 2–3 times when temperature rose to 310 K. A possible mechanism of such a temperature dependence based on the views on the activation caused by the intensification of the molecular motion is proposed. In the framework of these views, the analysis of the temperature dependence of the parameters that influence the efficiency of energy transfer, according to Förster's theory, was performed. It was shown that the main contribution to the observed experimental dependence was made by the change in the fluorescence quantum yield of quantum dots, and an additional contribution could be made by diffusion processes and effects of structural changes.

Resonance energy transfer in self-assembled hybrid structures formed by water-soluble semiconductor CdSe/ZnS quantum dots (QD) with a cysteine shell and the Exiguobacterium sibiricum retinal protein (ESR) in three modifications, with and without a 6-membered C-terminal histidine tag, and with both the histidine tag and C-terminal cysteine residue. Steady-state and time-resolved fluorescence spectroscopy was used to demonstrate that nonradiative energy transfer from QD onto the ESR protein depends on the strength of intermolecular interactions in the hybrid complex. A shift from electrostatic interactions in the QD-ESR donor-acceptor pair to coordinate bond with an additional disulfide bond resulted in an increase of the energy transfer efficiency from 40 to over 90%. The proposed method to produce noncovalent conjugates from QDs and light-sensitive proteins can be a promising one for biomedical applications, as well as for the development of new solar energy accumulation systems.