Heterodimerization of Group I Ribozymes Enabling Exon Recombination through Pairs of Cooperative trans‐Splicing Reactions

Group I (GI) self‐splicing ribozymes are attractive tools for biotechnology and synthetic biology. Several trans‐splicing and related reactions based on GI ribozymes have been developed for the purpose of recombining their target mRNA sequences. By combining trans‐splicing systems with rational modular engineering of GI ribozymes it was possible to achieve more complex editing of target RNA sequences. In this study we have developed a cooperative trans‐splicing system through rational modular engineering with use of dimeric GI ribozymes derived from the Tetrahymena group I intron ribozyme. The resulting pairs of ribozymes exhibited catalytic activity depending on their selective dimerization. Rational modular redesign as performed in this study would facilitate the development of sophisticated regulation of double or multiple trans‐splicing reactions in a cooperative manner.     

Use of real-time PCR to examine the relationship between ammonia oxidizing bacterial populations and nitrogen removal efficiency in a small decentralized treatment system 'Johkasou'.

The aim of this study was to examine the relationship between ammonia oxidizing bacterial populations and biological nitrogen removal in a small on-site domestic wastewater treatment system "Johkasou". The population dynamics of ammonia oxidizing bacteria (AOB) in six full-scale advanced Johkasous was surveyed using real-time PCR assay over a period of one year. These Johkasous were selected to compare the AOB populations in different treatment performance. When the effluent NH4-N concentration was higher than 2 mg L(-1), it was difficult to meet the effluent standard of advanced Johkasous (T-N 10 mg L(-1)). In contrast, the nitrogen removal efficiency was hardly affected by nitrite oxidation and denitrification in these systems. In other words, ammonia oxidation was a rate-limiting step. Furthermore, we focused on the relationship between NH4-N loading per AOB cell and nitrogen removal. Real time PCR monitoring results demonstrated that it is important to regulate NH4-N loading per AOB cell below 210 pg cell(-1) day(-1) to meet the effluent standard of advanced Johkasou. It is considered that NH4-N loading per AOB cell is a useful parameter for determining suitable nitrogen loading and small decentralized system design.     

Developments in asymmetric hydrogenation from an industrial perspective

Examples of developments in asymmetric hydrogenation from various perspectives, in an effort to improve efficiency, are reported. Discussed in this Account are (1) the improved synthesis of BINAP ligands, (2) the design of SEGPHOS ligands for higher enantioselectivity, (3) a new protocol with fewer reaction steps to synthesize beta-aminoesters, and (4) a novel asymmetric hydrogenation mediated by a copper catalyst.     

Low-dose SIMOX wafers for LSIs fabricated with internal-thermal-oxidation (ITOX) process: electrical characterization

Electrical performance of separation by implanted oxygen (SIMOX) wafers manufactured by internal-thermal-oxidation (ITOX) process was evaluated. Breakdown behaviour of the buried oxide (BOX) layer was confirmed quantitatively to be dominated by Si islands therein, which were found to be reduced in size or eliminated by the ITOX process. By optimizing the oxygen dose and ITOX amount, a BOX breakdown field of about 8 MV/cm, comparable to those of thermally-grown oxide, was attained. The gate oxide integrity on an ITOX-SIMOX wafer was found to be superior to that of bulk Si wafers, indicating the wafer surface was improved by the high temperature annealing.     

Short‐circuit phenomenon through hot gas ejected from molded case circuit breakers during high current interruption process and prevention of its occurrence

An experimental investigation on short‐circuit phenomenon through ejected hot gas between source‐side terminals in molded case circuit breakers (MCCBs) was performed. The rate of occurrence of the short‐circuit phenomenon was found to increase with the peak value of the breaking current and with the order of the breaking test. The conductance of the ejected hot gas was also found to rise with the peak value of the breaking current and with the order of the breaking test. These results indicate that the hot gas of high conductance is the cause of the short‐circuit phenomenon. Some effective means were taken in the MCCB to reduce the conductance of the hot gas. Decreasing the conductance of the hot gas successfully prevented the occurrence of short‐circuit phenomenon. © 2000 Scripta Technica, Electr Eng Jpn, 132(1): 22–29, 2000     

Dual Activity BLEG-1 from Bacillus lehensis G1 Revealed Structural Resemblance to B3 Metallo-β-Lactamase and Glyoxalase II: An Insight into Its Enzyme Promiscuity and Evolutionary Divergence

Metallo-β-lactamases (MBLs) are class B β-lactamases from the metallo-hydrolase-like MBL-fold superfamily which act on a broad range of β-lactam antibiotics. A previous study on BLEG-1 (formerly called Bleg1_2437), a hypothetical protein from Bacillus lehensis G1, revealed sequence similarity and activity to B3 subclass MBLs, despite its evolutionary divergence from these enzymes. Its relatedness to glyoxalase II (GLXII) raises the possibility of its enzymatic promiscuity and unique structural features compared to other MBLs and GLXIIs. This present study highlights that BLEG-1 possessed both MBL and GLXII activities with similar catalytic efficiencies. Its crystal structure revealed highly similar active site configuration to YcbL and GloB GLXIIs from Salmonella enterica, and L1 B3 MBL from Stenotrophomonas maltophilia. However, different from GLXIIs, BLEG-1 has an insertion of an active-site loop, forming a binding cavity similar to B3 MBL at the N-terminal region. We propose that BLEG-1 could possibly have evolved from GLXII and adopted MBL activity through this insertion.     

Application of femtosecond laser ablation for detaching grown protein crystals from glass capillary tube

We developed a novel technique for detaching protein crystals from glass capillary tube using the counter diffusion crystallization technique by femtosecond laser irradiation. X-ray diffraction analysis demonstrated that femtosecond laser irradiation has little effect on crystallinity. This technique will contribute to progress in structural genomics as a powerful tool.     

Development of a TES Microcalorimeter with a Mushroom Shaped Absorber Deposited on an Insulating Layer in an Overhang Region

A 3×3+1 superconducting transition-edge sensor (TES) microcalorimeter-array has been developed for the energy dispersive spectrometer performed on a transmission electron microscope. For increasing sensitive area, each TES microcalorimeter consisted of a Ti/Au bilayer and a mushroom shaped absorber. The mushroom shaped absorber is made from a Au layer of 0.5?μm thick. Geometrical dimensions of the surface area of the TES and the absorber are 350?μm×350?μm and 330?μm×330?μm, respectively. The absorber stem of 150?μm×150?μm in the cross sectional area is deposited on the center of the TES surface. A Ta₂O₅ insulating layer of 0.1?μm thick is inserted between the overhang layer of the absorber and the TES surface. One pixel of the TES microcalorimeter was operated for detecting X-ray photons emitted from an ⁵⁵Fe source.     

Status and research programs of the multinuclide accelerator mass spectrometry system at the University of Tsukuba

We present the current status and research programs of a multinuclide accelerator mass spectrometry (AMS) system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system), Japan. A maximum terminal voltage of 12 MV is available for the AMS system. The Tsukuba AMS system can measure environmental levels of long-lived radioisotopes of ¹⁴C, ²⁶Al, ³⁶Cl and ¹²⁹I by employing a molecular pilot beam. Recently, enhancements in AMS techniques and equipment, including sample preparation, the ion source and the data acquisition system, have improved the performance of ³⁶Cl-AMS. The standard deviation of fluctuations is typically ±2%, and the machine background level for the ³⁶Cl/Cl ratio is lower than 1 × 10^?15 with a halite sample. We have measured over 500 samples in 1 year, including samples for earth and environmental sciences and nuclear safety research.