No abstract

This report concerns physiological function of mycosporine-like amino acids (MAA) as an active defense against the photooxidative effects of sunlight in marine organisms. Mycosporine glycine (MG) is a representative member of MAA family and was found to effectively suppress various detrimental effects of the Type-II photosensitization in biological systems, such as inactivation of mitochondrial electron transport, lipid peroxidation of microsomes, hemolysis of erythrocytes and growth inhibition of Escherichia coli. The presence of MG in solutions of eosin Y or methylene blue resulted in a marked decrease in the level of singlet oxygen (1O2) produced by the sensitizers under illumination. The rate constant of 1O2 quenching by MG was determined to be 5.6 x 10(7) M(-1) s(-1) by the time-resolved 1O2 luminescence decay method, which is higher than, or at least comparable to, the values for 1O2 reaction of well-known quenchers such as 1,4-diazabicyclo[2,2,2]octane and furfuryl alcohol. The results suggest that MG probably together with some other active MAA may play an important role in protecting marine organisms against sunlight damage by eliminating 1O2 generated from certain endogenous photosensitizers.

Abstract— The photogeneration of singlet oxygen (1O2) from thylakoids and the chromophores involved as endogenous sensitizers were investigated using chloroplasts and thylakoids isolated from spinach. The blue light‐induced inhibition kinetics of photosynthetic electron transport and that of CTvCF, ATPase were also studied. The spectral dependence of the generation of 1O2 from thylakoid membranes, measured by the imidazole plus RNO method, clearly demonstrated that the Fe‐S centers play an important role in 1O2 generation, acting as sensitizers in thylakoids. The photoinhibition of the electron transport in isolated chloroplasts was strikingly depressed by a lipid‐soluble '02 quencher and enhanced by deuterium oxide substitution, indicating that the inhibition processes are mainly mediated by 1O2 which is produced via photodynamic activation. The involvement of chloroplast cytochromes in the production of 1O2 was deduced from the action spectrum for the photodynamic inhibition of the electron carrier chain. The results obtained from the kinetic studies appear consistent with the involvement of some components such as the Fe‐S centers and cytochrome chromophores of the carrier chain in the generation of 1O2.

No abstract

No abstract

A quantum confined transport based on a zinc oxide composite nanolayer that has conducting states with mobility edge quantization is proposed and was applied to develop multi-value logic transistors with stable intermediate states. A composite nanolayer with zinc oxide quantum dots embedded in amorphous zinc oxide domains generated quantized conducting states at the mobility edge, which we refer to as “mobility edge quantization”. The unique quantized conducting state effectively restricted the occupied number of carriers due to its low density of states, which enable current saturation. Multi-value logic transistors were realized by applying a hybrid superlattice consisting of zinc oxide composite nanolayers and organic barriers as channels in the transistor. The superlattice channels produced multiple states due to current saturation of the quantized conducting state in the composite nanolayers. Our multi-value transistors exhibited excellent performance characteristics, stable and reliable operation with no current fluctuation, and adjustable multi-level states.

No abstract

We have investigated the effects of insertion of a thin NiAl layer (≤0.63 nm) into a Co2FeGa0.5Ge0.5 (CFGG)/Ag interface on the magnetoresistive properties in CFGG/Ag/CFGG current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) pseudo spin valves (PSVs). First-principles calculations of ballistic transmittance clarified that the interfacial band matching at the (001)-oriented NiAl/CFGG interface is better than that at the (001)-Ag/CFGG interface. The insertion of 0.21-nm-thick NiAl layers at the Co2FeGa0.5Ge0.5/Ag interfaces effectively improved the magnetoresistance (MR) output; the observed average and the highest MR ratio (ΔRA) are 62% (25 mΩ μm2) and 77% (31 mΩ μm2) at room temperature, respectively, which are much higher than those without NiAl insertion. Microstructural analysis using scanning transmission electron microscopy confirmed the existence of thin NiAl layers at the Ag interfaces with only modest interdiffusion even after annealing at 550 °C. The improvement of the interfacial spin-dependent scattering by very thin NiAl insertion can be a predominant reason for the enhancement of the MR output.