No abstract

DJ‐1 family proteins have recently been characterized as novel glyoxalases, although their cofactor‐free catalytic mechanisms are not fully understood. Here, we obtained crystals of Arabidopsis thaliana DJ‐1d (atDJ‐1d) and Homo sapiens DJ‐1 (hDJ‐1) covalently bound to glyoxylate, an analog of methylglyoxal, forming a hemithioacetal that presumably mimics an intermediate structure in catalysis of methylglyoxal to lactate. The deuteration level of lactate supported the proton transfer mechanism in the enzyme reaction. Differences in the enantiomeric specificity of d/l‐lactacte formation observed for the DJ‐1 superfamily proteins are explained by the presence of a His residue in the active site with essential Cys and Glu residues. The model for the stereospecificity was further evaluated by a molecular modeling simulation with methylglyoxal hemithioacetal superimposed on the glyoxylate hemithioacetal. The mechanism of DJ‐1 glyoxalase provides a basis for understanding the His residue‐based stereospecificity. Database Structural data have been submitted to the Protein Data Bank under accession numbers http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OFW (structure of atDJ‐1d), http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OGF (structure of hDJ‐1 with glyoxylate) and http://www.rcsb.org/pdb/search/structidSearch.do?structureId=4OGG (structure of atDJ‐1d with glyoxylate).

A specific design for solution‐processed doping of active semiconducting materials would be a powerful strategy in order to improve device performance in flexible and/or printed electronics. Tetrabutylammonium fluoride and tetrabutylammonium hydroxide contain Lewis base anions, F− and OH−, respectively, which are considered as organic dopants for efficient and cost‐effective n‐doping processes both in n‐type organic and nanocarbon‐based semiconductors, such as poly[[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)] (P(NDI2OD‐T2)) and selectively dispersed semiconducting single‐walled carbon nanotubes by π‐conjugated polymers. The dramatic enhancement of electron transport properties in field‐effect transistors is confirmed by the effective electron transfer from the dopants to the semiconductors as well as controllable onset and threshold voltages, convertible charge‐transport polarity, and simultaneously showing excellent device stabilities under ambient air and bias stress conditions. This simple solution‐processed chemical doping approach could facilitate the understanding of both intrinsic and extrinsic charge transport characteristics in organic semiconductors and nanocarbon‐based materials, and is thus widely applicable for developing high‐performance organic and printed electronics and optoelectronics devices.

Electret and organic floating-gate memories are next-generation flash storage mediums for printed organic complementary circuits. While each flash memory can be easily fabricated using solution processes on flexible plastic substrates, promising their potential for on-chip memory organization is limited by unreliable bit operation and high write loads. We here report that new architecture could improve the overall performance of organic memory, and especially meet high storage for multi-level operation. Our concept depends on synergistic effect of electrical characterization in combination with a polymer electret (poly(2-vinyl naphthalene) (PVN)) and metal nanoparticles (Copper). It is distinguished from mostly organic nano-floating-gate memories by using the electret dielectric instead of general tunneling dielectric for additional charge storage. The uniform stacking of organic layers including various dielectrics and poly(3-hexylthiophene) (P3HT) as an organic semiconductor, followed by thin-film coating using orthogonal solvents, greatly improve device precision despite easy and fast manufacture. Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] as high-k blocking dielectric also allows reduction of programming voltage. The reported synergistic organic memory devices represent low power consumption, high cycle endurance, high thermal stability and suitable retention time, compared to electret and organic nano-floating-gate memory devices.

Dynamic Voltage Scaling (DVS), which adjusts the clock speed and supply voltage dynamically, is an effective technique in reducing the energy consumption of embedded real-time systems. Unlike dynamic-priority real-time scheduling for which highly effective DVS algorithms are available, existing fixed-priority DVS algorithms are less effective in energy efficiency because they are based on inefficient slack estimation methods. This paper describes an efficient on-line slack estimation heuristic for the rate-monotonic (RM) scheduling. The proposed heuristic estimates the slack times using the short term work-demand analysis. The DVS algorithm based on the proposed heuristic is also presented. Experimental results show that the proposed DVS algorithm reduces the energy consumption by 25∼42% over the existing rate-monotonic DVS algorithms.