Binding energetics of ferredoxin-NADP+ reductase with ferredoxin and its relation to function

To obtain insight into the motional features of proteins for enzymatic function, we studied binding reactions between ferredoxin-NADP(+) reductase (FNR) and ferredoxin (Fd) using isothermal titration calorimetry and NMR-based magnetic relaxation and hydrogen/deuterium exchange (HD(ex)). Fd-FNR binding was accompanied by endothermic reactions and driven by the entropy gain. Component-wise analysis of the net entropy change revealed that increases in the conformational entropy of the Fd-FNR complex contributed largely to stabilizing the complex. Intriguingly, analyses of magnetic relaxation and HD(ex) rates with X-ray B factor implied that Fd binding led to both structural stiffening and softening of FNR. Enhanced FNR backbone fluctuations suggest favorable contributions to the net conformational entropy. Fd-bound FNR further showed that relatively large-scale motions of the C terminus, a gatekeeper for interactions of NADP(+) (H), were quenched in the closed form, thereby facilitating exit of NADP(+) (H). This can provide a first dynamic structure-based explanation for the negative cooperativity between Fd and NADP(+) (H) via FNR.     

Low temperature hydrogen production by catalytic steam reforming of methane in an electric field

Catalytic steam reforming of methane in an electric field (electroreforming) at low temperatures such as 423 K was investigated. Pt catalysts supported on CeO₂, Ce_xZr_1−xO₂ solid solution and a physical mixture of CeO₂ and other insulators (ZrO₂, Al₂O₃ or SiO₂) were used for electroreforming. Among these catalysts, Pt catalyst supported on Ce_xZr_1−xO₂ solid solution showed the highest activity for electroreforming (CH₄ conv. = 40.6% at 535.1 K). Results show that the interaction among the electrons, metal loading, and catalyst support was important for high catalytic activity on the electroreforming. Catalytic activity of the electroreforming increased in direct relation to the input current. Characterizations using X-ray diffraction (XRD), temperature programmed reduction with H₂ (H₂-TPR), and alternate current (AC) impedance measurement show that the catalyst structure is an important factor for activity of electroreforming.     

Thermal Decomposition of Pentaerythritol Tetranitrate under Static High Pressure

The decomposition reaction of pentaerythritol tetranitrate (PETN), C(CH₂ONO₂)₄, under static high pressure was examined by conducting observations and infrared measurements up to 5 GPa at around 500 K. The thermal decomposition of PETN proceeded rapidly at around 500 K and formed a fluid consisting of N₂O, CO₂, and H₂O. The rate of the decomposition reaction at 423 K increased as the pressure increased, indicating a negative activation volume. The initial step of the decomposition reaction of PETN under static pressure was presumed to be the elimination of HNO₃.     

Laser spectroscopy of metastable antiprotonic helium atomcules

A new spectroscopic method for metastable antiprotonic helium atomcules by using a pulsed laser beam is proposed and discussed. It is shown that a metastable state can be resonantly destroyed to produce a detectable spike in a delayed annihilation time spectrum.     

Effect of algal extract on H2 production by a photosynthetic bacterium Rhodobium marinum A-501: analysis of stimulating effect using a kinetic model

We have established a system for hydrogen (H2) production from algal starch via lactic acid using a mixed culture of a lactic acid bacterium, Lactobacillus amylovorus, and a photosynthetic bacterium, Rhodobium marinum A-501. We found that the H2 production from lactate was stimulated in the presence of algal extract, which was obtained from algal biomass homogenate used as a substrate in the system by removing settleable solids including starch. To analyze the stimulating effect of algal extract on H2 production, we developed a kinetic model for H2 production by R. marinum A-501. The model revealed that approximately 20% of lactate was consumed for cell mass production, and the remaining portion was a source of reducing power to drive hydrogen production or other cellular processes. In the presence of algal extract, the model indicated that the conversion efficiency from lactate to the reducing power increased from 0.56 to 0.80 and nitrogenase activity increased up to twofold, resulting in the increase in yield of hydrogen from lactate from 29% to 48%. These results suggest that algal extract can attenuate the limitation process in lactate catabolism by which the supplementation of reducing power to drive H2 production was suppressed.     

Fabrication of Bi2Sr2CaCu2O x /Ag superconducting tape using a screen-printing method

High- T _c superconducting Bi₂Sr₂CaCu₂O _x /Ag tape was successfully fabricated using a screen-printing method and a partial-melting process. A highly oriented layer structure was achieved and confirmed by X-ray diffraction (XRD), pole-figure measurement and scanning electron microscopy (SEM). The critical current density, J _c, of the tape at 77 K, 0 T, was about 20000 A cm^–2. High-temperature XRD was used to clarify the mechanism of the grain alignment. An aligned structure of the 2212 phase was originated from Bi-free compounds, such as (Sr,Ca)CuO₂ and (Sr,Ca)₂CuO₃ developed during a holding stage at 875°C.     

Controlling chaos in a switched arrival system

We consider a switched arrival system with three buffers. We assume that the input rate of work and the processing time per unit are constant. Chase et al. show that the system is chaotic. In this article, we propose a method for stabilization of an unstable periodic orbit embedded in a chaotic attractor by changing the limited continuous processing time.     

Studies on thermal degradation of synthetic polymers. XV. Estimation of the product yield on the basis of intensity function for thermal gasification of isotactic and atactic polypropylenes

The kinetic equation for the pyrolysis gasification reaction of isotactic and atactic polypropylenes has been established. The difference in tacticity of the samples does not much affect the kinetic parameters. The exponent a of the intensity function I_F = Tδ^a (K·sec^a), concerning the severity of decomposition conditions, has been approximated as 0.039 (isotactic) and 0.040 (atactic), respectively from the kinetic parameters in this experiment. The calculated values of the product yield from Arrhenius equations, k = 2.0 × 10¹⁰ exp(?40.9 × 10³/RI_F) (isotactic) and k = 1.2 × 10¹⁰ exp(–41.4 × 10³/RI_F) (atactic), for the I_F standard agree with the experimental values.     

Efficiency of hydrogen transferring liquefaction of a subbituminous coal using hydrogenated fluoranthene for short contact time at high temperature and low pressure

An Australian subbituminous coal (Wandoan) was effectively liquefied at 490 and 510 °C under nitrogen pressure of 2.5 MPa for 1.0–7.5 min using 1, 2, 3, 3a-tetrahydrofluoranthene (4HFL) as a hydrogen-donating solvent. The yields of oil and asphalthene could be as high as 58 and 24 wt%, respectively. The content of 4HFL was very influential on the oil yield although under appropriate liquefaction conditions, a considerable amount remained after reaction. The kinetics of the reaction and analytical study of the products and the solvent suggest consecutive as well as instantaneous depolymerization in the process. The coking or recondensation reaction was very rapid after 4HFL was consumed, confirming the efficacy of the short contact time liquefaction.