Tibor Szabó

Photosynthetic Machineries in Nano-Systems

Photosynthetic reaction centres are membrane-spanning proteins, found in several classes of autotroph organisms, where a photoinduced charge separation and stabilization takes place with a quantum efficiency close to unity. The protein remains stable and fully functional also when extracted and purified in detergents thereby biotechnological applications are possible, for example, assembling it in nano-structures or in optoelectronic systems. Several types of bionanocomposite materials have been assembled by using reaction centres and different carrier matrices for different purposes in the field of light energy conversion (e.g., photovoltaics) or biosensing (e.g., for specific detection of pesticides). In this review we will summarize the current status of knowledge, the kinds of applications available and the difficulties to be overcome in the different applications. We will also show possible research directions for the close future in this specific field.

Using Central Composite Experimental Design to Optimize the Degradation of Tylosin from Aqueous Solution by Photo-Fenton Reaction

The feasibility of the application of the Photo-Fenton process in the treatment of aqueous solution contaminated by Tylosin antibiotic was evaluated. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to evaluate and optimize the effect of hydrogen peroxide, ferrous ion concentration and initial pH as independent variables on the total organic carbon (TOC) removal as the response function. The interaction effects and optimal parameters were obtained by using MODDE software. The significance of the independent variables and their interactions was tested by means of analysis of variance (ANOVA) with a 95% confidence level. Results show that the concentration of the ferrous ion and pH were the main parameters affecting TOC removal, while peroxide concentration had a slight effect on the reaction. The optimum operating conditions to achieve maximum TOC removal were determined. The model prediction for maximum TOC removal was compared to the experimental result at optimal operating conditions. A good agreement between the model prediction and experimental results confirms the soundness of the developed model.

Photosynthetic reaction centers/ITO hybrid nanostructure

Photosynthetic reaction center proteins purified from Rhodobacter sphaeroides purple bacterium were deposited on the surface of indium tin oxide (ITO), a transparent conductive oxide, and the photochemical/-physical properties of the composite were investigated. The kinetics of the light induced absorption change indicated that the RC was active in the composite and there was an interaction between the protein cofactors and the ITO. The electrochromic response of the bacteriopheophytine absorption at 771 nm showed an increased electric field perturbation around this chromophore on the surface of ITO compared to the one measured in solution. This absorption change is associated with the charge-compensating relaxation events inside the protein. Similar life time, but smaller magnitude of this absorption change was measured on the surface of borosilicate glass. The light induced change in the conductivity of the composite as a function of the concentration showed the typical sigmoid saturation characteristics unlike if the photochemically inactive chlorophyll was layered on the ITO. In this later case the light induced change in the conductivity was oppositely proportional to the chlorophyll concentration due to the thermal dissipation of the excitation energy. The sensitivity of the measurement is very high; few picomole RC can change the light induced resistance of the composite.

Structural and Functional Hierarchy in Photosynthetic Energy Conversion—from Molecules to Nanostructures

Basic principles of structural and functional requirements of photosynthetic energy conversion in hierarchically organized machineries are reviewed. Blueprints of photosynthesis, the energetic basis of virtually all life on Earth, can serve the basis for constructing artificial light energy-converting molecular devices. In photosynthetic organisms, the conversion of light energy into chemical energy takes places in highly organized fine-tunable systems with structural and functional hierarchy. The incident photons are absorbed by light-harvesting complexes, which funnel the excitation energy into reaction centre (RC) protein complexes containing redox-active chlorophyll molecules; the primary charge separations in the RCs are followed by vectorial transport of charges (electrons and protons) in the photosynthetic membrane. RCs possess properties that make their use in solar energy-converting and integrated optoelectronic systems feasible. Therefore, there is a large interest in many laboratories and in the industry toward their use in molecular devices. RCs have been bound to different carrier matrices, with their photophysical and photochemical activities largely retained in the nano-systems and with electronic connection to conducting surfaces. We show examples of RCs bound to carbon-based materials (functionalized and non-functionalized single- and multiwalled carbon nanotubes), transitional metal oxides (ITO) and conducting polymers and porous silicon and characterize their photochemical activities. Recently, we adapted several physical and chemical methods for binding RCs to different nanomaterials. It is generally found that the P+(QAQB)− charge pair, which is formed after single saturating light excitation is stabilized after the attachment of the RCs to the nanostructures, which is followed by slow reorganization of the protein structure. Measuring the electric conductivity in a direct contact mode or in electrochemical cell indicates that there is an electronic interaction between the protein and the inorganic carrier matrices. This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications.

Thermal Effects and Structural Changes of Photosynthetic Reaction Centers Characterized by Wide Frequency Band Hydrophone: Effects of Carotenoids and Terbutryn.

Photothermal characteristics and light‐induced structural (volume) changes of carotenoid‐containing and noncontaining photosynthetic reaction centers (RCs) were investigated by wide frequency band hydrophone. We found that the presence of carotenoid either does not play considerable role in the light‐induced conformational movements, or these rearrangements are too slow for inducing a photoacoustic (PA) signal. The kinetic component with a few tens of microseconds, exhibited by the carotenoid‐less RCs, appears to be similar to that of triplet state lifetimes, identified by other methods. The binding of terbutryn to the acceptor side is shown to affect the dynamics of the RC. Our results do not confirm large displacements or volume changes induced by the charge movements and by the charge relaxation processes in the RCs in few hundreds of microseconds time scale that accompanies the electron transfer between the primary and secondary electron acceptor quinones.

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

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 (QB) site albeit to slightly different places. Different herbicide molecules have different binding affinities (evaluated as inhibition constants, KI, and binding enthalpy values, ΔHbind). 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 KI and ΔHbind 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, 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 QB 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.

Monitoring of fetal heart rate via iPhone

Recording of fetal heart rate can be reassuring for the mother about the fetus’ wellbeing. Our smart phone application can detect, record and evaluate fetal heart rate at any time. This method is based on sound wave thus free from the effects of ultrasound, and can be used all day without harming the fetus. It does not require medical assistance and easy to use at home. It reduces the queue at outpatient care units, helps pregnant women to relieve stress by listening to their unborn baby’s heartbeat. It improves mother-child relationship yet sends an alarming message if further examinations are needed to prevent the consequences of hypoxia.

Real-Time Sensing of Hydrogen Peroxide by ITO/MWCNT/Horseradish Peroxidase Enzyme Electrode

The accurate and sensitive determination of H2O2 is very important in many cases because it is a product of reactions catalysed by several oxidase enzymes in living cells and it is essential in environmental and pharmaceutical analyses. The fabrication of enzyme protein activity based biosensors is a very promising way for this purpose because the function of biological molecules is very specific, sensitive, and selective. Horseradish peroxidase HRP is the most commonly used enzyme for H2O2 detection because it can oxidize hydrogen atoms and, for example, xenobiotics in the presence of H2O2. In order to define the limit of detection LOD of H2O2 we made calibrations with guaiacol and amplex red AR, which are hydrogen donors of HRP. The accumulation of the reaction products, tetraguaiacol, and resorufin, respectively, then can be easily detected by absorption or emission fluorescence spectroscopy. In our experiments an enzyme electrode was fabricated from ITO indium tin oxide, functionalized multiwalled carbon nanotubes f-MWCNTs, and HRP. Although the enzyme activity was smaller by about two orders of magnitude when the enzyme was bound to the f-MWCNTs ca. 10−2 M H2O2/M HRP·sec compared to ca. 2 M H2O2/M HRP·sec and 5 M H2O2/M HRP·sec with AR and guaiacol in buffer solution, LOD of the H2O2 decomposition was about 6 pM H2O2/sec and 10 pM H2O2/sec in the case of AR and guaiacol, respectively.

The end and renewal of ideology in Central Europe and in Hungary

Abstract Society has to be understood as a process of fast changes (revolutions) and slow transformations (reformism). This is what has been happening in Central Europe, where the big changes of 1989–1990 were preceded by several small social, political and ideological transformations. When analysing Central European societies, one should also remember that there is an ‘official’ society and a ‘hidden’ society. In addition, the relation of state and civil society is deformed since in most cases the civil sphere is repressed and undeveloped due to the predominance of the ‘official state’. In such societies, you cannot find real hegemony but only dominance, which is practiced by the state not only in the sphere of economy, society and culture, but also in and through ideology. The essence of modern totalitarian society cannot be understood without addressing the permanent existence of unofficial, ‘civil’ ideologies penetrating the ‘hidden’ society at the same time as the ‘official’ ideology. Apart from the slow transformation of ideologies and the crisis of ‘official’ ideology, the strengthening of ‘hidden’ ideology is also required for revolutionary changes. This is how a historically new situation with new ideologies can come into being, in clear contrast to the renewal of old ideologles, which generates a mixture of the old and the new. A look at what happened in Central Europe, but particularly Hungary, should clarify the point.

Functional Nanohybrid Materials from Photosynthetic Reaction Center Proteins

Application of technical developments in biology and vice versa or biological samples in technology led to the development of new types of functional, so-called “biohybrid” materials. These types of materials can be created at any level of the biological organization from molecules through tissues and organs to the individuals. Macromolecules and/or molecular complexes, membranes in biology, are inherently good representatives of nanosystems since they fall in the range usually called “nano.” Nanohybrid materials provide the possibility to create functional bionanohybrid complexes which also led to new discipline called “nanobionics” in the literature and are considered as materials for the future. In this publication, the special characteristics of photosynthetic reaction center proteins, which are “nature’s solar batteries,” will be discussed in terms of their possible applications for creating functional molecular biohybrid materials.