PTERIN- AND FLAVIN-LIKE FLUORESCENCE ASSOCIATED WITH ISOLATED FLAGELLA OF Euglena gracilis

Fluorescence excitation- and emission spectra indicate the presence of pterin(s) and flavin(s) in isolated flagella of the phytoflagellate Euglena gracilis. These compounds appear to bind at least in part non-covalently to the molecular framework of the paraflagellar body, which is the presumed photoreceptor organelle and which is attached to the isolated flagella. A compound with pterin-like fluorescence excitation and emission spectrum could he extracted with methanol from isolated flagella and could he recovered on thin-layer silica gels. Besides the previously assumed photoreceptor function of flavins, our results suggest also a role for pterins in the photosensory transduction chain of Euglena gracilis.     

Error Bounds for Hermite Interpolation by Quadratic Splines on an {alpha}-Triangulation

For l, an -triangulation F of a planar domain is such that,for every T F, there holds 1 R_T/2r_T , where R_T (resp. r_T)denotes the radius of the circumscribed (resp. inscribed) circleof the triangle T. When T is varying in F the centre of itsinscribed circle is varying in a compact interior to T and itsorthogonal projections on the sides are varying in compact intervalsinterior to these sides. Precise results are given about thesizes of these compacts and are used for the computation oferror constants in the problem of Hermite interpolation by Powell-Sabinquadratic finite elements, bringing to the fore their dependenceon the parameter .     

RUTHENIUM RED INHIBITION OF OXYGEN EVOLUTION AND SPECIFIC RELEASE OF THE EXTRINSIC 16 kDa POLYPEPTIDE IN A PHOTOSYSTEM II PREPARATION

The inhibitory effect of the dye ruthenium red was studied in photosystem II-enriched submembrane fractions. A number of distinct types of interaction were found, which differed in their concentration range and required incubation time. Ruthenium red instantaneously quenches the initial chlorophyll a fluorescence level (F₀) and the maximum fluorescence level (F_m) by enhancing radiationless deactivation in the chlorophyll light harvesting complex. Associated with this quenching of fluorescence is an instantaneous decrease in the quantum yield of oxygen evolution. Ruthenium red also inhibited the light saturated rate of oxygen evolution and the variable fluorescence, monitored 80 µs after a saturating excitation-flash. These inhibitions increased with incubation time and became greater than 50% within 5 min. Although ruthenium red was known to affect Ca²⁺ or Cl^? sites specifically, the inhibitory action was more pronounced than simple Ca²⁺ or Cl^? depletion. Incubation with ruthenium red for 5 min blocks the Z P680⁺ → Z⁺ P680 charge transfer reaction. Upon mixing with the photosystem II preparation, ruthenium red induced specific release of the extrinsic 16 kDa polypeptide associated with water-splitting without release of Mn. It is proposed that the inhibitor produces an ionic imbalance which alters the configuration of the donor side of photosystem II.     

Adsorption of Hydrazoic Acid on Pristine Graphyne Sheet: A Computational StudySCI北大核心CSCD

Herein we have investigated the interaction between hydrazoic acid(HN3) and a pristine graphyne system based on density functional theory(DFT) method using generalized gradient approximation. The van der Waals dispersion correction is also considered for predicting the possibility of using the graphyne system for detection of hydrazoic acid. Pristine graphyne has a band gap of 0.453 eV, which decreases to 0.424 eV when HN3 is adsorbed on graphyne. The electrical conductivity of HN3-adsorbed graphyne is greater than that of its pristine counterpart. Charge transfer analysis reveals that the HN3-adsorbed graphyne system behaves as an n-type semiconductor; however, its pristine analogue acts as an intrinsic semiconductor. Pristine graphyne has zero dipole moment; however, its interaction with HN3 increases its dipole moment. The electronic properties of graphyne is significantly influenced by the presence of HN3, leading to the possibility of designing graphyne-based sensors for HN3 detection.