The circadian clock modulates water dynamics and aquaporin expression in Arabidopsis roots.

We have developed a plant growth system to analyze water dynamics in the roots of a small model plant, Arabidopsis thaliana, by nuclear magnetic resonance (NMR) microscopic imaging. Using the two-dimensional slice technique, we obtained a series of images with high signal-to-noise ratio indicating the water distribution in the root. To demonstrate light regulation of water transport in the root and involvement of aquaporin gene expression, we visualized the distribution of water in Arabidopsis roots under various light conditions and compared the data with the expression profiles of two aquaporin genes.

Arrayed silicon prism coupler for a terahertz-wave parametric oscillator.

Using room-temperature parametric oscillation of a LiNbO3 crystal pumped by a Q-switched Nd:YAG laser with a simple configuration, we have realized a widely tunable coherent terahertz- (THz-) wave source in the range between 1 and 3 THz. Inasmuch as the THz wave is affected by total internal reflection at the crystal edge, we used a Si prism coupler to couple out the THz wave. We introduce an arrayed Si-prism coupler that increases the efficiency and decreases the diffraction angle.

Tunable terahertz-wave generation from DAST crystal by dual signal-wave parametric oscillation of periodically poled lithium niobate.

The first known demonstration of tunable terahertz-wave generation by difference-frequency generation of dual signal-wave quasi-phase-matched optical parametric oscillation was performed with periodically poled LiNbO(3) (PPLN) with a series of gratings. An organic ionic salt, 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST), was used as a nonlinear crystal. A compact terahertz-wave source resulted, and changing the temperature of the PPLN permitted the wavelength to be varied from 120 to 160 microm.

Exotic radiation from a photonic crystal excited by an ultrarelativistic electron beam.

We report the observation of an exotic radiation (unconventional Smith-Purcell radiation) from a one-dimensional photonic crystal. The physical origin of the exotic radiation is direct excitation of the photonic bands by an ultrarelativistic electron beam. The spectrum of the exotic radiation follows photonic bands of a certain parity, in striking contrast to the conventional Smith-Purcell radiation, which shows solely a linear dispersion.

Light induced structural changes of a full-length protein and its BLUF domain in YcgF(Blrp), a blue-light sensing protein that uses FAD (BLUF).

Blue-light sensing proteins that use FAD (BLUF) are members of a blue-light receptor family that is widely distributed among microorganisms. The Escherichia coli YcgF protein is a BLUF protein consisting of the N-terminal FAD-binding hold (BLUF domain) and the C-terminal EAL domain. The EAL domain of YcgF is predicted to have cyclic-di-GMP phosphodiesterase activity.

Action spectrum for expression of the high intensity light-inducible Lhc-like gene Lhl4 in the green alga Chlamydomonas reinhardtii.

Lhl4 encodes a distant relative of light-harvesting Chl-a/b proteins in the green alga Chlamydomonas reinhardtii. Lhl4 mRNA markedly accumulated within 30 min after illumination and in proportion to the light intensity up to a fluence rate much higher than that required for photosynthesis. The high intensity light (HL)-induced accumulation of Lhl4 mRNA required continuous illumination, and the mRNA level rapidly decreased when the cells were placed in the dark.

Inelastic photoemission due to scattering by surface adsorbate vibrations.

By measuring the very low energy photoemission spectra of the CO/Cu(001) surface with a high resolution, we have found the energy loss components due to inelastic scattering of electrons near the Fermi level by the CO vibrational modes. The main energy loss structure appears as a step at 254 meV below the Fermi edge for 12C16O. An isotope shift of the step to 240 meV was observed when 13C18O was adsorbed.

The mechanism of photochemical 1,3-silyl migration of allylsilane.

The photochemical reaction mechanisms of model compounds for 4-tert-butyl-1-(4-phenylphenyl)-1-(1,1-dimethylallyl)silacyclohexane are investigated using a complete active space comprised of six electrons in six orbitals with the standard 6-31G(d) basis set. It is concluded that the stereochemistry in the photochemical 1,3-silyl migrations of allylsilanes has a retention preference, in accord with the Woodward-Hoffmann rules. The calculated conical intersection (CI) structure suggests a dissociation path to radicals in addition to a 1,3-shift path.

Flexural rigidity of individual microtubules measured by a buckling force with optical traps.

We used direct buckling force measurements with optical traps to determine the flexural rigidity of individual microtubules bound to polystyrene beads. To optimize the accuracy of the measurement, we used two optical traps and antibody-coated beads to manipulate each microtubule. We then applied a new analytical model assuming nonaxial buckling.

FTIR detection of structural changes in a histidine ligand during S-state cycling of photosynthetic oxygen-evolving complex.

Changes in structural coupling between the Mn cluster and a putative histidine ligand during the S-state cycling of the oxygen-evolving complex (OEC) have been detected directly by Fourier transform infrared (FTIR) spectroscopy in photosystem (PS) II core particles from the cyanobacterium Synechocystis sp. PCC6803, in which histidine residues were selectively labeled with l-[(15)N(3)]histidine. The bands sensitive to the histidine-specific isotope labeling appeared at 1120-1090 cm(-)(1) in the spectra induced upon the first-, second-, and fourth-flash illumination, for the S(2)/S(1), S(3)/S(2), and S(1)/S(0) differences, at similar frequencies with different sign and/or intensity depending on the respective S-state transitions.

Changes in structural and functional properties of oxygen-evolving complex induced by replacement of D1-glutamate 189 with glutamine in photosystem II: ligation of glutamate 189 carboxylate to the manganese cluster.

A carboxylate group of D1-Glu-189 in photosystem II has been proposed to serve as a direct ligand for the manganese cluster. Here we constructed a mutant that eliminates the carboxylate by replacing D1-Glu-189 with Gln in the cyanobacterium Synechocystis sp. PCC 6803, and we examined the resulting effects on the structural and functional properties of the oxygen-evolving complex (OEC) in photosystem II.

Studies on photosynthetic oxygen-evolving complex by means of Fourier transform infrared spectroscopy: calcium and chloride cofactors.

Structural roles of functional Ca2+ and Cl- ions in photosynthetic oxygen-evolving complexes (OEC) were studied using low- (640-350 cm-1) and mid- (1800-1200 cm-1) frequency S2/S1 Fourier transform infrared (FTIR) difference spectroscopy. Studies using highly active Photosystem (PS) II core particles from spinach enabled the detection of subtle spectral changes. Ca2+-depleted and Ca2+-reconstituted particles produced very similar mid- and low-frequency spectra.

Adenylyl cyclase activity of Cya1 from the cyanobacterium Synechocystis sp. strain PCC 6803 is inhibited by bicarbonate.

Bicarbonate stimulates the activities of several class III adenylyl cyclases studied to date. However, we show here that bicarbonate decreased V(max) and substrate affinity in Cya1, a major adenylyl cyclase in the cyanobacterium Synechocystis sp. strain PCC 6803.

Density functional theory calculations on the dielectric constant dependence of the oxidation potential of chlorophyll: implication for the high potential of P680 in photosystem II.

The primary donor chlorophyll (Chl) of photosystem II (PSII), P680, has an extremely high oxidation redox potential (E(ox)) of approximately 1.2 V, which is essential for photosynthetic water oxidation. The mechanism for achieving a high potential such as that of P680 has been one of the central questions in photosynthesis research.

Water-sensitive low-frequency vibrations of reaction intermediates during S-state cycling in photosynthetic water oxidation.

In photosynthetic water oxidation, two water molecules are converted to an oxygen molecule through five reaction intermediates, designated S(n) (n = 0-4), at the catalytic Mn cluster of photosystem II. To understand the mechanism of water oxidation, changes in the chemical nature of the substrate water as well as the Mn cluster need to be defined during S-state cycling. Here, we report for the first time a complete set of Fourier transform infrared difference spectra during S-state cycling in the low-frequency (670-350 cm(-1)) region, in which interactions between the Mn cluster and its ligands can be detected directly, in PS II core particles from Thermosynechococcus elongatus.

High-transmission waveguide with a small radius of curvature at a bend fabricated by use of a circular photonic crystal.

A bent photonic crystal waveguide was fabricated by use of a lattice pattern of a circular photonic crystal that allowed high transmission for a broad band of wavelengths with a small radius of curvature at a bend. The waveguide was fabricated by use of alumina rods with a diameter of 3 mm. Windows of high transmission as a result of waveguiding were observed near 9 and 15 GHz.

Light-induced structural changes of apoprotein and chromophore in the sensor of blue light using FAD (BLUF) domain of AppA for a signaling state.

AppA is a new class blue-light receptor controlling photosynthesis gene expression in the purple bacterium Rhodobacter sphaeroides and retains a characteristic flavin adenine dinucleotide (FAD)-binding domain named the "sensor of blue light using FAD" (BLUF). AppA functions as an antirepressor controlling transcription of photosynthesis genes through the direct association with a transcriptional repressor PpsR in a blue-light-dependent manner [Masuda and Bauer (2002) Cell 110, 613-623]. Illumination of AppA induces a red shift in the UV-visible absorption of FAD, which results in a signaling state of AppA.

Spectroscopic analysis of the dark relaxation process of a photocycle in a sensor of blue light using FAD (BLUF) protein Slr1694 of the cyanobacterium Synechocystis sp. PCC6803.

Slr1694 is a BLUF (sensor of blue light using flavin adenine dinucleotide) protein and a putative photoreceptor in the cyanobacterium Synechocystis sp. PCC6803. Illumination of Slr1694 induced a signaling light state concurrent with a red shift in the UV-visible absorption of flavin, and formation of the bands from flavin and apo-protein in the light-minus-dark Fourier transform infrared (FTIR) difference spectrum.

Structural intermediate in the photocycle of a BLUF (sensor of blue light using FAD) protein Slr1694 in a Cyanobacterium Synechocystis sp. PCC6803.

Slr1694 in Synechocystis sp. PCC6803 is a family of blue-light photoreceptors based on flavin adenine dinucleotide (FAD) called BLUF (sensor of blue light using FAD) proteins, which include AppA from Rhodobacter sphaeroides and PAC from Euglena gracilis. Illumination of dark-state Slr1694 at 15 degrees C reversibly induced a signaling light state characterized by the red shift in the UV-visible spectrum and by the light-induced Fourier transform infrared (FTIR) difference spectrum for structural changes of a bound flavin and apo protein.

Changes in the functional and structural properties of the Mn cluster induced by replacing the side group of the C-terminus of the D1 protein of photosystem II.

A free alpha-COO(-) in the C-terminal alanine-344 (Ala344) in the D1 protein of photosystem II is thought to be responsible for ligating the Mn cluster. The effects of the side group of the C-terminus of the D1 protein on the functional and structural properties of the oxygen-evolving complex (OEC) were comprehensively studied by replacing Ala344 with glycine (Gly), valine (Val), aspartate (Asp), or asparagine (Asn). All the mutants grew photoautotrophically under low-light conditions with lower O(2) evolution activity depending on the mutants when compared with the activity of the control wild type.

Structural changes of D1 C-terminal alpha-carboxylate during S-state cycling in photosynthetic oxygen evolution.

Changes in the chemical structure of alpha-carboxylate of the D1 C-terminal Ala-344 during S-state cycling of photosynthetic oxygen-evolving complex were selectively measured using light-induced Fourier transform infrared (FTIR) difference spectroscopy in combination with specific [(13)C]alanine labeling and site-directed mutagenesis in photosystem II core particles from Synechocystis sp. PCC 6803. Several bands for carboxylate symmetric stretching modes in an S(2)/S(1) FTIR difference spectrum were affected by selective (13)C labeling of the alpha-carboxylate of Ala with l-[1-(13)C]alanine, whereas most of the isotopic effects failed to be induced in a site-directed mutant in which Ala-344 was replaced with Gly.

Internal axial light conduction in the stems and roots of herbaceous plants.

In order to reveal any roles played by stems and roots of herbaceous plants in responding to the surrounding light environment, the optical properties of the stem and root tissues of 18 herbaceous species were investigated. It was found that light was able to penetrate through to the interior of the stem and was then conducted towards the roots. Light conduction was carried out within the internodes and across the nodes of the stem, and then in the roots from the tap root to lateral roots.

Biochemical characterization of the major adenylyl cyclase, Cya1, in the cyanobacterium Synechocystis sp. PCC 6803.

We report herein the biochemical properties of an adenylyl cyclase, Cya1, from the cyanobacterium Synechocystis sp. PCC 6803. Heterologously expressed Cya1 catalyzed cyclic AMP formation with a Km for ATP of approximately 2.

High-intensity-light-dependent and transient expression of new genes encoding distant relatives of light-harvesting chlorophyll-a/b proteins in Chlamydomonas reinhardtii.

We identified four Lhc-like genes (Lhl) encoding proteins that are distant relatives of light-harvesting chlorophyll a/b-binding (LHC) proteins in the green alga Chlamydomonas reinhardtii. Their mRNA levels after transfer from low-intensity light to high-intensity light (HL) were examined and compared with those of Lhc genes encoding LHC proteins of PSII. The transfer caused a decrease in the mRNA level of Lhl3, a homolog of Arabidopsis thaliana Lil3, within 2 h, followed by gradual restoration depending on the intensity of HL.