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

Szabó T, Magyar M, Hajdu K, Dorogi M, Nyerki E, Tóth T, Lingvay M, Garab G, Hernádi K, Nagy L - Nanoscale Res Lett (2015)

Bottom Line: 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.This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics and Informatics, University of Szeged, Rerrich B. tér 1., H-6721, Szeged, Hungary. tiberatosz@gmail.com.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Comparison of basic photochemical and photophysical characteristics of chlorophyll-a and bacteriochlorophyll-a. The redox middle potential, Em, in dichloromethane and the wavelength of the absorption maxima, Amax, in the red and near infrared are also indicated. For comparison, the Em of several characteristic redox couples are also indicated. Redox couples: P680/P680+: ground state PS-II primary donor; H2O/O2: water/oxygen; P870/P870+: ground state bacterial RC primary donor; H2O2/O2: hydrogen peroxide/oxygen; P680*/P680+: excited state PS-II primary donor; P870*/P870+: excited state purple bacterial RC primary donor
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Fig2: Comparison of basic photochemical and photophysical characteristics of chlorophyll-a and bacteriochlorophyll-a. The redox middle potential, Em, in dichloromethane and the wavelength of the absorption maxima, Amax, in the red and near infrared are also indicated. For comparison, the Em of several characteristic redox couples are also indicated. Redox couples: P680/P680+: ground state PS-II primary donor; H2O/O2: water/oxygen; P870/P870+: ground state bacterial RC primary donor; H2O2/O2: hydrogen peroxide/oxygen; P680*/P680+: excited state PS-II primary donor; P870*/P870+: excited state purple bacterial RC primary donor

Mentions: The photosynthetic energy conversion begins with the absorption of light by the photosynthetic pigments, most notably by chlorophyll molecules. The special biological and chemical functions of chlorophylls are determined by their molecular structures, containing highly delocalized conjugated molecular orbitals (Figs. 1 and 2). The energy difference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is reflected in the spectroscopically measurable S0 → S1 transition which is about 660 nm for chlorophyll-a in organic solution (see Fig. 2). Chlorophyll-a is a redox-active pigment with a redox mid-potential of Em ≈ 500 mV in organic solution. When the chlorophylls are bound to proteins (e.g. in the photosynthetic reaction centre (RC) protein, the site of primary photochemistry), the Em is shifted to a more positive (oxidizing) value, Em = 1200 mV. It is interesting to note that this is the most oxidizing redox system in living cells and fulfils the energetic requirements of water splitting; the Em of water/oxygen system is Em = 820 mV.Fig. 1


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

Szabó T, Magyar M, Hajdu K, Dorogi M, Nyerki E, Tóth T, Lingvay M, Garab G, Hernádi K, Nagy L - Nanoscale Res Lett (2015)

Comparison of basic photochemical and photophysical characteristics of chlorophyll-a and bacteriochlorophyll-a. The redox middle potential, Em, in dichloromethane and the wavelength of the absorption maxima, Amax, in the red and near infrared are also indicated. For comparison, the Em of several characteristic redox couples are also indicated. Redox couples: P680/P680+: ground state PS-II primary donor; H2O/O2: water/oxygen; P870/P870+: ground state bacterial RC primary donor; H2O2/O2: hydrogen peroxide/oxygen; P680*/P680+: excited state PS-II primary donor; P870*/P870+: excited state purple bacterial RC primary donor
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4666181&req=5

Fig2: Comparison of basic photochemical and photophysical characteristics of chlorophyll-a and bacteriochlorophyll-a. The redox middle potential, Em, in dichloromethane and the wavelength of the absorption maxima, Amax, in the red and near infrared are also indicated. For comparison, the Em of several characteristic redox couples are also indicated. Redox couples: P680/P680+: ground state PS-II primary donor; H2O/O2: water/oxygen; P870/P870+: ground state bacterial RC primary donor; H2O2/O2: hydrogen peroxide/oxygen; P680*/P680+: excited state PS-II primary donor; P870*/P870+: excited state purple bacterial RC primary donor
Mentions: The photosynthetic energy conversion begins with the absorption of light by the photosynthetic pigments, most notably by chlorophyll molecules. The special biological and chemical functions of chlorophylls are determined by their molecular structures, containing highly delocalized conjugated molecular orbitals (Figs. 1 and 2). The energy difference between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is reflected in the spectroscopically measurable S0 → S1 transition which is about 660 nm for chlorophyll-a in organic solution (see Fig. 2). Chlorophyll-a is a redox-active pigment with a redox mid-potential of Em ≈ 500 mV in organic solution. When the chlorophylls are bound to proteins (e.g. in the photosynthetic reaction centre (RC) protein, the site of primary photochemistry), the Em is shifted to a more positive (oxidizing) value, Em = 1200 mV. It is interesting to note that this is the most oxidizing redox system in living cells and fulfils the energetic requirements of water splitting; the Em of water/oxygen system is Em = 820 mV.Fig. 1

Bottom Line: 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.This can be a basis of sensing element of bio-hybrid device for biosensor and/or optoelectronic applications.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Physics and Informatics, University of Szeged, Rerrich B. tér 1., H-6721, Szeged, Hungary. tiberatosz@gmail.com.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus