Swertisin dihydrate

The title compound, 6‐C‐gluco­pyran­osyl‐7‐O‐methyl­apigenin dihydrate, C₂₂H₂₂O₁₀·2H₂O, is a natural C‐glu­cosyl­flavone. The flavone skeleton is almost planar, the dihedral angle between the pyran moiety and the 4‐hydroxy­phenyl ring being 9.8 (3)°. The basal plane of the pyran­osyl ring of the glucose moiety is almost perpendicular to the benzo­pyran ring system. The flavone skeletons are stacked along the a axis, forming layers parallel to (001). Between these hydro­phobic layers, the glucose groups and water mol­ecules of crystallization are connected via O—H⋯O hydrogen bonds, forming hydro­philic layers.     

Dynamic light‐scattering measurement of sieving polymer solutions for protein separation on SDS CE

We evaluated the mesh size and homogeneity of polymer network by dynamic light scattering and discussed the relationship between the physical properties of polymer network and the protein separation behavior by capillary polymer electrophoresis. We compared three kinds of sieving polymers in solutions with a wide range of molecular weights and concentrations: polyacrylamide and polyethylene oxide as flexible polymers, and hydroxyethyl cellulose as a semiflexible polymer. We found that the mobility of protein was dominated primarily by the mesh size ξ, irrespective of the type of sieving polymers, and the peak spacing between protein peaks increased drastically in the range of ξ<10 nm, where the mobility also decreased. And the peak widths were dependent on the molecular species of sieving polymers and their homogeneity of polymer network. We proposed that a polymer network with a homogenous mesh size of less than 10 nm is the best sieving medium for separation of the proteins in the molecular weight range 14 300–97 200 Da from the view point of the resolution in protein separation.     

Roles of K151 and D180 in L‐2‐haloacid dehalogenase from Pseudomonas sp. YL: Analysis by molecular dynamics and ab initio fragment molecular orbital calculations

L ‐2‐haloacid dehalogenase (L ‐DEX) catalyzes the hydrolytic dehalogenation of L ‐2‐haloalkanoic acids to produce the corresponding D ‐2‐hydroxyalkanoic acids. This enzyme is expected to be applicable to the bioremediation of environments contaminated with halogenated organic compounds. We analyzed the reaction mechanism of L ‐DEX from Pseudomonas sp. YL (L ‐DEX YL) by using molecular modeling. The complexes of wild‐type L ‐DEX YL and its K151A and D180A mutants with its typical substrate, L ‐2‐chloropropionate, were constructed by docking simulation. Subsequently, molecular dynamics (MD) and ab initio fragment molecular orbital (FMO) calculations of the complexes were performed. The ab initio FMO method was applied at the MP2/6‐31G level to estimate interfragment interaction energies. K151 and D180, which are experimentally shown to be important for enzyme activity, interact particularly strongly with L ‐2‐chloropropionate, catalytic water, nucleophile (D10), and with each other. Our calculations suggest that K151 stabilizes substrate orientation and balances the charge around the active site, while D180 stabilizes the rotation of the nucleophile D10, fixes catalytic water around D10, and prevents K151 from approaching D10. Further, D180 may activate catalytic water on its own or with K151, S175, and N177. These roles are consistent with the previous results. Thus, MD and ab initio FMO calculations are powerful tools for the elucidation of the mechanism of enzymatic reaction at the molecular level and can be applied to other catalytically important residues. The results obtained here will play an important role in elucidating the reaction mechanism and rational design of L ‐DEX YL with improved enzymatic activity or substrate specificity. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009     

Amelioration of Airway Stenosis in Rabbit Models by Photodynamic Therapy with Talaporfin Sodium (NPe6)

It is difficult to treat patients with acquired airway stenosis, and the quality of life of such patients is therefore lowered. We have suggested the application of photodynamic therapy (PDT) as a new treatment for airway stenosis and have determined the efficacy of PDT in animal disease models using a second-generation photosensitizer with reduced photosensitivity. An airway stenosis rabbit model induced by scraping of the tracheal mucosa was administered NPe6 (5 mg kg⁻¹), and the stenotic lesion was irradiated with 670 nm light emitted from a cylindrical diffuser tip at 60 J cm⁻² under bronchoscopic monitoring. PDT using NPe6 improved airway stenosis ( P  = 0.043) and respiratory stridor. A significant prolongation of survival time was seen in the PDT-treated animals compared to that in the untreated animals ( P  = 0.025) and 44% of the treated animals achieved long-term survival (>60 days). In conclusion, PDT using NPe6 is effective for improvement in airway stenosis.     

Exemplary mathematics instruction and its development in selected education systems in East Asia

What may teachers do in developing and carrying out exemplary or high-quality mathematics classroom instruction? What can we learn from teachers’ instructional practices that are often culturally valued in different education systems? In this article, we aim to highlight relevant issues that have long been interests of mathematics educators worldwide in identifying and examining teachers’ practices in high-quality mathematics classroom instruction, and outline what articles published herein can help further our understanding of such issues with cases of exemplary mathematics instruction valued in the Chinese Mainland, Hong Kong, Japan, Singapore, South Korea, and Taiwan.     

Metal to insulator transition in films of molecularly linked gold nanoparticles

We report a metal to insulator transition (MIT) in disordered films of molecularly linked gold nanoparticles (NPs). As the number of carbons (n) of alkanedithiol linker molecules (C(n)S2) is varied, resistance (R) at low temperature (T = 2 K) and at 200 K, as well as trends in R vs T data at intermediate temperatures, all point to an MIT occurring at n = 5. We describe these results in a context of a Mott-Hubbard MIT. We find that all insulating samples (n > or = 5) exhibit a universal scaling behavior R approximately exp[(T0/T)nu] with nu = 0.65, and all metallic samples (n < or = 5) exhibit weaker R-T dependencies than bulk gold. We discuss these observations in terms of competitive thermally activated processes and strong, T-independent elastic scattering, respectively.     

Signal quality improvement of holographic data storage using adaptive two-dimensional filter

Holographic data storage is being widely studied for the purpose of developing next-generation large optical memories. A prospective use of this type of memory is in building image archives in large-scale data centers. In particular, demand for energy conservation at data centers, and therefore for holographic data storage, is growing. In holographic data storage, interference between bits occurs owing to wave aberration in the optical system, shrinkage of the medium, and crosstalk noise from neighboring holograms during multiplex recording; as a result of the interference, the reproduced image deteriorates and the bit error rate (BER) increases. In this study, to reduce the BER in both off-axis-type recording and coaxial-type recording, a two-dimensional finite impulse response (FIR) filter is applied to a reproduced image that has been recorded by angle multiplex recording and shift multiplex recording. First, for the optimization of the FIR filter coefficients, the linear minimum mean square error (LMMSE) method is applied; this method optimizes the coefficients by reducing the BER. Furthermore, for evaluating the optimization performance of the LMMSE method, the optimization performance is compared with that of the real-coded genetic algorithm (RCGA), which has the capability to search a wide range of coefficients. The optimization by the LMMSE method has been found to be excellent for off-axis-type recording but not for coaxial-type recording. It is speculated that this is because of the brightness irregularity in the reproduced image, resulting from crosstalk. On the other hand, a marked reduction in the BER is observed using the RCGA, despite the brightness irregularity. In this study, the effectiveness of the LMMSE method for signals recorded by coaxial-type recording, in which large brightness irregularity is expected, is examined using automatic gain control (AGC). It is found that the application of AGC reduces the BER even in the case of coaxial-type recording.     

DNA碱基激光拉曼光谱检测方法的研究

以激光拉曼光谱仪采集腺嘌呤(A)、鸟嘌呤(G)、胞嘧啶(C)、胸腺嘧啶(T)的拉曼光谱图,分析了各碱基谱峰归属,并依据归属结果检测混合碱基组成。结果显示:4种碱基的特征峰集中在175～1 800cm~(-1)。相同积分时间和激光功率条件下,该波段内嘌呤碱基的激光拉曼光谱峰高于嘧啶碱基的谱峰。腺嘌呤、鸟嘌呤、胞嘧啶、胸腺嘧啶分别在723、648、791、1 368 cm~(-1)处的谱峰最强,利用这些特征峰能在2min内鉴别出混合碱基中的各碱基。     

New sights into the electrochemical interface provided by in situ X-ray absorption fine structure and surface X-ray scattering

Various important processes, such as electron transfer reactions, adsorption/desorption, solvation/desolvation, and formation/cleavage of chemical bonds, take place at electrolyte/electrode interfaces during electrocatalytic reactions. Those processes have been understood on the basis of changes in the surface composition, atomic arrangement, and molecular and electronic structures of the interfaces by using various in situ analysis techniques. To date, in situ analysis and observation of those interfacial processes at an ideal single-crystal surface are indispensable not only for fundamental understanding of the reaction mechanism but also for rational design of the highly efficient and durable electrocatalytic materials. Here, historical and recent progress of in situ studies on electrocatalytic reactions is briefly reviewed with a focus on two major techniques, X-ray absorption fine structure and surface X-ray scattering.     

Demonstration of highly efficient broadband amplification in a optical parametric chirped-pulse amplifier system

We have demonstrated highly efficient broadband amplification by an optical parametric chirped pulse amplifier (OPCPA) system that uses high energy seed pulses. The OPCPA consists of three type I B-barium borate (BBO) crystals pumped by a Q-switched Nd:YAG laser. We successfully amplified the microjoule level seed pulses to 78 mJ with a pump-to-signal optical conversion efficiency of 26% at a 10 Hz repetition rate. To our knowledge these results represent the most optically efficient OPCPA to date pumped by a typical Q-switched laser.