Protein nanotubes with an enzyme interior surface

This report describes the synthesis and enzyme activities of multilayered protein nanotubes with an α-glucosidase (αGluD) interior surface. The nanotubes were prepared by using an alternating layer-by-layer (LbL) assembly of human serum albumin (HSA) and oppositely charged poly-L-arginine (PLA) into a track-etched polycarbonate (PC) membrane (pore size=400 nm) followed by addition of αGluD as the last layer of the wall. Subsequent dissolution of the PC template yielded (PLA/HSA)(2)PLA/αGluD nanotubes. SEM measurements revealed the formation of uniform hollow cylinders with (413±17) nm outer diameter and (52±3) nm wall thickness. In aqueous media, the nanotubes captured a fluorogenic glucopyranoside, 4-methyl-umbelliferyl-α-D-glucopyranoside (MUGlc), into their one-dimensional pore space and hydrolyzed the substrate efficiently to form α-D-glucose. We determined the enzyme parameters (Michaelis constant, K(M), and catalytic constant, k(cat), values) of the protein nanotubes. The several-micrometers-long cylinders were of sufficient length to be spun down by centrifugation at 4000 g, so the product could therefore be easily separated. Similar biocatalysts were prepared by complexation of biotinylated-αGluD into HSA-based nanotubes bearing a single avidin layer as an internal surface. The obtained hybrid nanotubes also exhibited the same enzyme activity for the MUGlc hydrolysis.     

掺杂As2S8非晶态薄膜波导的光阻断效应

实验研究了未掺杂和低浓度掺锡和掺磷的As₂S₈薄膜波导的光阻断效应,提供了三种样品的光阻断响应曲线、室温退激实验数据和光谱测试数据. 结果表明,掺锡样品可以明显提升毫秒级响应的快过程恢复作用,同时还具有减少残留传输损耗的效果,掺磷的效果则相反. 结合实验结果给出了分析讨论. 关键词： 光波导技术 硫属化合物玻璃 光阻断效应 掺杂     

On Electron Spin Polarization Created in the Excited Triplet State of Accessory Chlorophyll via Photoinduced Charge-Recombination of the Photosystem II Reaction Center

We present a theoretical approach to investigate the electron spin polarization (ESP) of the excited triplet state that has been detected using the time-resolved electron paramagnetic resonance (TREPR) method in the photosystem II center of the plants. We show, using the stochastic Liouville equation, that the ESP pattern created in the accessory chlorophyll (Chl_accD1) which reside near the P_D1 chlorophyll of the active branch is explained by one-step, concerted double electron transfer model, initiating from the singlet–triplet conversion of the light-induced charge-separated state composed of P_D1 radical cation and pheophytin radical anion. We also considered the sequential ESP transfer model via the triplet charge-recombination (CR) and the triplet–triplet energy transfer processes. It has been clearly shown that the ESP created in the ³Chl_accD1* is dependent on the rate constant (k _TT) of the triplet–triplet energy transfer from the intermediate triplet state created by the CR. Also we show that the relative orientation of the principal axes of the spin dipolar interaction in the intermediate triplet state (³P_D1*, as an example) may play a role in the ESP pattern, when the k _TT is smaller than the angular frequency of the Zeeman energy. We have theoretically shown that the TREPR measurement of the ESP is very powerful to investigate the primary chemical process and to characterize the intermediate as a signature of the stepwise ESP transfer.     

Microcrystalline silicon–germanium thin films prepared by the chemical transport process using hydrogen radicals

We propose microcrystalline silicon–germanium (μc-SiGe) as a bottom cell material of triple-junction solar cells in order to improve the conversion efficiency of thin film solar cells. The μc-SiGe thin films were prepared by the chemical transport process using Si and Ge targets exposed to hydrogen radicals. We successfully produced highly photosensitive μc-SiGe films with relatively low Ge composition by increasing the gas pressure, and observed the photovoltaic effect in pin solar cell structures. However, it was difficult to produce μc-SiGe films with higher Ge composition. We found that a small amount of argon introduction into the chemical transport process enables us to increase Ge composition at the high pressure. Moreover, the argon introduction seems effective to maintain the electrical properties in relatively high Ge composition. The results suggest that the μc-SiGe thin films prepared by the chemical transport process are one of the candidates for new photovoltaic materials.     

Oxygen-binding to simple cobaltporphyrins combined with polyvinylmidazole

Reversible oxygen-binding was observed at low temperature for the poly(vinylimidazole-co-octyl methacrylate) complexes of the simple or planar cobaltporphyrins (CoP) such as cobalt-tetraphenylporphyrin and cobalt-octaethylporphyrin. The oxygen-binding affinity and rate constants were compared with those for the cobalt-picketfence porphyrin, a typical oxygen-carrier. The low oxygen-binding affinity for the CoP complexes was attributed to the enormously large oxygen-releasing rate constant.