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A supramolecular triad constructed via axially coordinating imidazole-appended fulleropyrrolidine was shown to be successful model of the photosynthetic antenna-reaction center complex. Efficient energy transfer successfully mimics the combined antenna-reaction center in the natural photosynthesis process.

Research has been conducted on the molecules with the head of precise spacer, shape and label moieties. The synthesis and characterization of these molecules are described.

Research shows that in photosynthetic reaction centers of purple bacteria, conformational changes limit the electron transfer from the reduced primary quinone to the secondary quinone. Further, the electron transfer is not affected by shortening the secondary quinone tail from 50 to 5 carbons but it slows when the quinone position is shifted.

Analysis of the ground-state electronic structures of the 'special pair' bacteriochlorophyll dimer reveals three bacteriochlorophyll species with comparable chemical shifts and one bacteriochlorophyll exhibiting a different shift. Data indicate that the structural changes of the special pair do not impact reorganization energy associated with the charge-transfer process.

Research shows that the properties of P700 are modulated by the hydrogen bond to the 13(sup)1-keto group of chlorophyll a', suggesting that the polarity of the binding pocket influence P700. Furthermore, the oxidation potential of chlorophyll a' is enhanced if the keto group is hydrogen bonded to Thr A739 residue.

The X-ray absorption fine structure indicates that three di-mu-oxo manganese-manganese motifs may be present in the photosystem II oxygen evolving complex as revealed by the heterogeneity of the S(sub)o state in the 2.7 angstrom manganese-manganese distances.

At least three chlorophyll triplet populations are present in thylakoids that are associated with photosystem II as shown by fluorescence-detected magnetic resonance spectrosopy. The triplets are seen in aerated samples and are formed under nonreducing redox conditions with two generating in the core complex(es) and the other in the external antenna.

Research identifies five unique polypeptides in cyanobacterial photosystem II complex in the HT-3 strain of Synechocystis sp. PCC 6803. The proteins include the SII1638 protein, a homologue of the PsbQ protein, which is present in chloroplast photosystem II complex.

Research has been conducted on the meso, meso-linked porphyrin dimer. The incorporation of this dimer as the light-harvesting chromophore into the photosynthetic electron transfer model in constructing ferrocene-meso, meso-linked porphyrin dimer-fullerene triad is reported.

Research has been conducted on the Ca (super)2+ depletion. The structural and functional roles of Ca (super)2+ in the photosynthetic evolution of oxygen have been investigated and are discussed in the article.

Research has been conducted on the S-cycle redox transition of the photosystem II oxygen evolving complex. The pH dependence of this redox transition has been investigated via the electron paramagnetic resonance spectroscopy and the results are reported.

Results do not support the temperature dependence theory proposed for the reduction of P680 in photosystem II reactions of photosynthesis. Authors discuss microsecond time scale and nanosecon phase level of proton-coupled electron transfer reactions and the energies these reactions generate to support their claim.

Results point out that phosphatidylglycerol is indispensable for the structure and function of photosystem reaction center complex and for the structural integrity of the plastoquinone electron acceptor Q(sub)B-binding site. Data show that the lipid deprivation inactivates the electron acceptors in the reaction center.

The S state-dependent chlorophyll fluorescence in the nitric oxide-treated photosystem II exhibits a three-flash downshift, whereas in the electron paramagnetic resonance, the maximum S(sup)-2 signal manifests after the fourth flash. Results suggest that manganese cluster is in a redox state after treatment of photosystem II with nitric oxide.

Results reveal pronounced excitonic interactions between chlorophyll a and b molecules, suggesting that the spectral heterogeneity of a minor photosystem II antenna complex includes contribution of the chlorophyll molecules as well as the contribution from the pigment-protein interactions.

Research has been conducted on the photosynthetic reaction centers. The effect of the identity, energy of the functional substrates and the barriers between the functional substrates on the protein reaction coordinates has been investigated and is described.

Research demonstrates that moderately hydrated photosystem II films in glycerol/water solution, enable measurement of S-state transition difference spectra of the whole water hydroxyl region by Fourier transform infrared spectroscopy. Data indicate that the S-state cycle in these hydrated films is similar to the core samples in solution.

The pigment-protein interactions in the photosystem II antenna protein, Lhcb4, reveal that removal of a any bound cofactor from any sites of the chlorophyll a binding sites, a2, a4, and a5 leads to a loss of bands of the particular chlorophyll molecule and a structural impact on the protein folding.

Research examines the spectral heterogeneity of chlorophylls in the light harvesting complex II of photosynthetic apparatus. Low temperature absorption spectroscopy of a recombinant LHC-II complex reveals that chlorophylls at specific binding sites can be correlated with distinct spectral sub-bands, representing absorption spectra of native and refolded LHC-II complex.

Research has been conducted on the Mn atoms which function as catalysts in the water-oxidizing complex in the PS II oxidizing site. The effect of the PS II proteins' amine groups on the photoligation of the Mn (super)2+ to the apo water-oxidizing complex has been investigated via photoactivation and chemical modification techniques and the results are discussed.

Research has been conducted on the rhenium(I) polypyridine maleimide complexes. The synthesis, photophysical properties and characterization of these complexes have been carried out and the results of the X-ray crystal structure analysis are presented.

Research has been conducted on the ferredoxin-NADP (super)+ reductase. The distinct forms of this reductase have been expressed in the photosynthetic and nonphotosynthetic plant tissues and the structural and kinetic properties of the nonphotosynthetic isoform examined in defining characteristics related to the tissue-specific function are reported.

Results demonstrate that quenching of chlorophyll fluorescence of the light-harvesting complexes of photosystem II is influenced by protein-protein interactions within thylakoid membranes. The intrasubunit conformational change and intersubunit interactions within the lipid membranes are discussed.

Results demonstrate the presence of 2 beta-carotenes with each arranged in parallel or perpendicular to the membrane plane in the pheophytin modified photosystem II reaction center protein. Data indicate that the 'core' pigments include two Pheo and four Chl, which absorb in the 676-685 nanometer range.

Research has been conducted on the S (sub)3 state of the oxygen-evolving complex in photosystem II. The EPR signal induced by a pH jump to alkaline pH in the S (sub)3 state of this complex has been investigated and the results are discussed.

Research demonstrates that the thermodynamic properties of photosystem II core reaction centers of the cyanobacterium Synechocystis sp. PCC 6803 markedly differ from those of bacterial and photosystem I reaction centers.

Research describes interactions between bicarbonate and the Q(sub)B binding site in photosystem II as measured by iron redox-spectra in relation to 0-phenanthroline. Results show that a hydrogen bond network from the non heme iron toward the Q(sub)B pocket involves bicarbonate and histidine D1-215.

Results reveal the dynamic structural changes in the secondary structure of the oxygen evolving complex during successive S-state transitions. Data indicate that the oscillatory pattern of the spectra is due to changes in the amide I and II regions, which reflect the rearrangement of H-bonding partners within photosystem II.

Fourier transform infrared difference spectra show four oscillation patterns for the photosystem II. The flash-induced spectra reveal the individual S-state transitions comprising of symmetric and asymmetric stretching regions of carboxylate groups and amide I region.

Results show that spectral properties and photochemical behavior of xanthophyll pigments are reflections of the individual pigments bound to the light-harvesting complexes. Data on the absorption wavelengths and fluorescence of the bound pigments are discussed.

Results show that illumination at low-temperature generates a mixture of chlorophyll and carotenoid radicals in photosystem II. Data indicate that carotenoid radicals are less stable for recombination while chlorophyll radicals exhibit strong absorption peaks at near-infrared regions. Upon warming the pigments show interconversion between 6 to 120 K.

Results demonstrate that the amino acid changes introduced into the CD-loop region of the photosystem II D2 protein, by combinatorial mutagenesis, result in two charge recombination pathways in photosystem II. Data indicate that the pathways cause changes in the energy gap between redox forms of P680.

Results describe the crystal structural aspects of photosystem II protein complex from the cyanobacterium Synechococcus vulcanus. Data reveal that the crystal is a dimer with an apparent molecular mass of 580 kilo Daltons. The crystal diffracts maximally at 3.5 angstroms and belong to orthorhombic type.

Research reveals that phosphatidyl glycerol and digalactosyl diacylglycerol of the thylakoid membranes interact with light-harvesting complex of photosystem II folding, assembly and stability. Data indicate that the two lipids along with monogalactosyl diacylglycerol stabilize the complex against thermal denaturation.

Results indicate a retardation of the rate of transfer of the excitation energy from the peripheral chlorophyll of photosystem II D2 polypeptide to the electron-transfer pigments. Data further show that the chlorophyll associated with His117 of D2 is important for excitation energy transfer to the electron-transfer pigments.

Research has been conducted on the free energy of the first electron transfer. The numerical calculations of this free energy are presented.

Research was conducted to determine the arrangement of the iron-sulfur clusters F(sub X/A/B)- relative to P700+ by generating electron paramagnetic resonance signals from charge-separated spin pairs (P700+-F(super red)(sub X/A/B)) in photosystem I and characterizing them via progressive microwave power saturation calculations. Results provide evidence that iron-sulfur cluster F(sub A) is in closer proximity to P700 than the F(sub B) cluster.

Research was conducted to examine the role of the water chains in the proton conduction processes in the photosynthetic reaction center from Rhodobacter sphaeroides. In particular, the study focused on the effect of the presence of various side chains at the position L209 on the functional properties of the reaction center. Results are discussed based on the disorganization of the hydrogen-bonded network caused by the presence of aromatic residues at the position L209 that leads to decreased electron and proton-transfer capabilities.

Electron paramagnetic resonance spectroscopy was used in studying the effect of copper and zinc ions on manganese-depleted photosystem II (PS II). Copper and zinc ions were shown to have similar effects on PS II systems although a higher concentration of zinc ions was needed to elicit the same effect as the copper ions. The differing redox and binding behavior of the copper ions in the iron site in PS II compared to its behavior in the bacterial reaction center is seen as further proof of the varying iron coordination in the two systems.

Electron paramagnetic resonance spectroscopy has been utilized in the study of the manganese cluster of photosystem II (PSII) found in Synechococcus elongatus. The study, conducted by administering a number of saturating laser flashes in the presence of either ethanol or methanol, detected S multiline signals in plant PSII and in S. elongatus that were similar but not identical. The magnetic relaxation characteristics of an oxidized low-spin heme was also shown to vary with the S states.

The functionality of PsaF with respect to the photosystem I complex is diminished due to a displacement of the N-terminal domain of the subunit. This is evident in an experiment in which the psaJ chloroplast gene of the green alga Chlamydomonas reinhardtii was inactivated either in a wild-type or in a PsaF-deficient nuclear background. The N-terminal domain of PsaF is exposed in the lumenal space in the absence of PsaJ when the domain is cross-linked to Pc and Cyt c(sub 6). It is suggested that PsaJ maintains PsaF in a proper orientation and results in fast electron transfer from soluble donor proteins to P700(super +).

Enantioselective photocyclization of N-alkylfuran-2-carboxyanilides to trans-dihydrofuran derivatives was examined in inclusion crystals with optically active hose compounds derived from tartaric acid. X-ray structural analysis of inclusion crysals was used to study the mechanism of the enantioselective reaction of achiral compounds in inclusion crystals. The results suggested that in some cases, the steric course of the photoreaction vary depending on the types of preparation of inclusion crystals.

An experiment reports a novel crystal-engineering design strategy to imbed practically unlimited numbers of porphyrin chromophores in desirable, controlled metalation states into highly organizable, rigid, one-dimensional and/or two-dimensional crystalline, supramolecular arrays. The approach enables a virtually limitless number of metal ions to be inserted into the polymeric porphyrin arrays and is therefore relevant to the design of light harvesting model systems.

The monomeric spin density distribution in the primary electron donor of photosystem I was investigated using electron magnetic resonance spectroscopy. Comprehensive electron nuclear double resonance and electron spin-echo envelope modulation experiments were used along with isotropic substitution and numerical simulations to determine the electronic structure of the primary electron donor. Results showed that the unpaired electron spin in the primary donor is entirely localized on one of the chlorophylls in the dimer pair.

The role of pigment-protein interactions in determining the properties of photosystem II was investigated. To this end, site-directed mutants of Synechocystis PCC 6803 were prepared which alter the reduction-oxidation potential of the primary radical pair anion and cation. Experimental results showed that the mutations alter the free energy of the primary radical pair state, resulting in a change in the equilibrium between excited singlet states and radical pair states.

The effect of herbicide binding on the reduction-oxidation potential of the plastoquinone acceptor in Photosystem II was investigated. Experimental results showed that phenolic herbicides reduce the reduction-oxidation potential while DCMU increases it. These effects were demonstrated in changes in the peak temperature of thermoluminescence bands resulting from the recombination of charge pairs involving the plastoquinone. The changes induced by herbicide binding were consistent with previous results showing that phenolic herbicides enhance the sensitivity of Photosystem II to light.

Manganese oxidation of the oxygen-evolving compound for the S0-S1, S1-S2 and S2-S3 transitions of the water oxidation cycle was investigated. The oxygen-evolving derivative was driven through its functional cycle, the S-state cycle, using microsecond light flashes. The S-state population distribution was analyzed through X-ray absorption spectroscopy on layered photosystem (PS) II membrane particles. It was proposed that cycling of the PS II manganese compound through four distinct oxidation states of the tetranuclear manganese complex results in photosynthetic oxygen evolution.

The oxidation of phenol-imidazole hydrogen-bonded compounds was investigated using the hybrid density functional method. Tyrosine oxidation in oxygenic photosynthesis was modeled by phenol while the histidine residue was modeled by imidazole. Hybrid density functional computations showed that one-electron oxidation of a phenol-imidazole hydrogen-bonded compound results in spontaneous transfer of the phenolic proton to the imidazole. This spontaneous transfer of the phenolic proton leads to the formation of a phenoxyl radical-imidazolium ion compound.

Light-harvesting arrays composed of one, two or eight boron-dipyrrin pigments and one porphyrin have been designed and synthesized using a modular building block method. The arrays are soluble in organic solvents and have been characterized by time-resolved and static absorption and fluorescence spectroscopy. Results showed that the strong blue-green absorption of the boron-dipyrrin accessory pigment is complementary to the spectral characteristics of the free base or zinc porphyrin, proving the high efficiency of the light-harvesting arrays in photonics.

Experiments were performed to identify two chlorophyll-ligating histidines, D1-H118 and D2-H117, as ligands to accessory chlorophylls in the reaction center of photosystem II (PSII). Results showed that D1-H118 was the axial ligand to the redox-active chlorophyll Z, while D2-H117 was identified as the axial ligand of the redox-inactive accessory chlorophyll. These results illustrate the two-fold structural symmetry of PSII similar to those shown in redox-active tyrosines.