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(+)(Q(A)Q(B))(−) 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

Separation of electrophysiologically distinct neuronal populations in the rat hippocampus for neuropharmacological testing under in vivo conditions

Microiontophoresis combined with extracellular spike recording is an excellent method for investigating local neuropharmacological effects under in vivo conditions. However, its application has recently become relatively rare in neuroscience research. Now, we aimed to revisit microiontophoresis and demonstrate that it provides valuable data about the pharmacophysiology of neurons and local neuronal networks, in vivo. Extracellular recordings were performed through the central recording channel of multibarrel carbon-fiber microelectrodes in the CA1 pyramidal layer of the hippocampus of anesthetized rats, while N-methyl-D-aspartate (NMDA) was locally administrated by means of microiontophoresis through the surrounding micropipettes of the microelectrode. Various separation procedures were used to distinguish putative pyramidal cells and interneurons. Quality of separation was verified by electrophysiological parameters. After the delivery of NMDA in the vicinity of the examined neurons, firing rate of putative pyramidal cells was increased with a significantly higher grade then that of putative interneurons. The present results in line with previous data indicate that pyramidal cells are more responsive to pharmacological manipulation through NMDA receptors, also confirming the reliability of the separation of different types of neurons in in vivo microiontophoretic experiments

Immunological and pharmacological identification of the dopamine D1 receptor in the CNS of the pond snail, Lymnaea stagnalis

We investigated the presence and distribution of the D1 dopamine receptor in the CNS of Lymnaea stagnalis applying immunobloting and immunocytochemistry. We also investigated the effect of dopamine as well as the specific D1 receptor blocker, SCH23390, on the firing activity of the feeding modulator serotonergic neuron, CGC, which displayed D1 immunoreactivity. Immunoblot experiments showed one specifically labeled band with 62 kDa mw which is close to that of the mammalian D1 receptor. Neurons displaying D1-like immunoreactivity can be observed in each ganglion of the CNS but particularly in the pedal ganglia which are the center for locomotion. Dopamine regularly evokes burst activity in the serotonergic CGC at 1 mM and this effect could be antagonized by SCH23390. These observations suggest that a D1-like receptor molecule is present in the CNS of Lymnaea

Automatic detection of trustworthiness of the face: A visual mismatch negativity study

Recognizing intentions of strangers from facial cues is crucial in everyday social interactions. Recent studies demonstrated enhanced event-related potential (ERP) responses to untrustworthy compared to trustworthy faces. The aim of the present study was to investigate the electrophysiological correlates of automatic processing of trustworthiness cues in a visual oddball paradigm in two consecutive experimental blocks. In one block, frequent trustworthy (p = 0.9) and rare untrustworthy face stimuli (p = 0.1) were briefly presented on a computer screen with each stimulus consisting of four peripherally positioned faces. In the other block stimuli were presented with reversed probabilities enabling the comparison of ERPs evoked by physically identical deviant and standard stimuli. To avoid attentional effects participants engaged in a central detection task. Analyses of deviant minus standard difference waveforms revealed that deviant untrustworthy but not trustworthy faces elicited the visual mismatch negativity (vMMN) component. The present results indicate that adaptation occurred to repeated unattended trustworthy (but not untrustworthy) faces, i.e., an automatic expectation was elicited towards trustworthiness signals, which was violated by deviant untrustworthy faces. As an evolutionary adaptive mechanism, the observed fast detection of trustworthiness-related social facial cues may serve as the basis of conscious recognition of reliable partners

Automatic detection of trustworthiness of the face: A visual mismatch negativity study

Recognizing intentions of strangers from facial cues is crucial in everyday social interactions. Recent studies demonstrated enhanced event-related potential (ERP) responses to untrustworthy compared to trustworthy faces. The aim of the present study was to investigate the electrophysiological correlates of automatic processing of trustworthiness cues in a visual oddball paradigm in two consecutive experimental blocks. In one block, frequent trustworthy (p = 0.9) and rare untrustworthy face stimuli (p = 0.1) were briefly presented on a computer screen with each stimulus consisting of four peripherally positioned faces. In the other block stimuli were presented with reversed probabilities enabling the comparison of ERPs evoked by physically identical deviant and standard stimuli. To avoid attentional effects participants engaged in a central detection task. Analyses of deviant minus standard difference waveforms revealed that deviant untrustworthy but not trustworthy faces elicited the visual mismatch negativity (vMMN) component. The present results indicate that adaptation occurred to repeated unattended trustworthy (but not untrustworthy) faces, i.e., an automatic expectation was elicited towards trustworthiness signals, which was violated by deviant untrustworthy faces. As an evolutionary adaptive mechanism, the observed fast detection of trustworthiness-related social facial cues may serve as the basis of conscious recognition of reliable partners