The aerobic methylation of arsenic by microorganisms in the presence of l-methionine-methyl-d3

The microorganisms Scopulariopsis brevicaulis, Candida humicola, and Gliocladium roseum growing aerobically, methylate a range of arsenic compounds to produce R′R″As(CH₃) (R′  R″  CH₃; R′  n-C₄H₉, R″  CH₃). When l-methionine-methyl-d₃ is added to the cultures the CD₃ label is incorporated, intact, in the evolved arsine to a considerable extent, indicating that S-adenosylmethionine or some related sulphonium compound is involved in the biological process.     

尿素刀豆生物传感器的研制

本文报告了尿素刀豆生物传感器的制备和性能。斜率46.0—49.7mv.dec~(-1)、线性范围2×10~(-4)—5×10~(-3)mol.L~(-1),检测下限2.5×10~(-5)mol.L~(-1)。该传感器用于血液中尿氮含量的测定,此测定结果与分光光度法测定结果无明显差异。     

对甲苯磺酸催化合成乳酸异戊酯

报道了对甲苯磺酸在异戊醇和乳酸酯化反应中的应用 ,讨论了合成条件。实验表明其催化活性良好。     

A qualitative test for detection of ferroelectricity in crystalline powder

By use of the pyroelectric temperature analysis (PTA) of the unsintered pressed powder samples in the temperature region of the phase transition it is possible to determine the value of the electric charge released during the transition. The comparison of results of the transition charges obtained from unpoled as well as from poled samples can differentiate a ferroelectric from nonferroelectric material. The proposed method is successfully validated with KH₂PO₄, (NH₄)₂SO₄ and NH₄H₂PO₄ pressed powder.     

Exact energy principle in magnetic reconnection for current-sheet models

On the basis of an exact nonlinear energy principle, it is shown that the change in magnetic topology (i.e., reconnection) in a finite-domain system leads to the conversion of magnetic field energy to particle energy. However, it is also shown that the conversion efficiency gradually disappears as the system size increases. This principle is demonstrated with model current-sheet equilibria including Harris and Fadeev solutions, as well as a current-sheet equilibrium which contains a singular current layer. The finding that energy conversion in reconnection is highly dependent on the system size may have an important implication for numerical simulations performed under finite geometry.     

Spectral domain embedding for elliptic PDEs in complex domains

Spectral methods are a class of methods for solving partial differential equations (PDEs). When the solution of the PDE is analytic, it is known that the spectral solutions converge exponentially as a function of the number of modes used. The basic spectral method works only for regular domains such as rectangles or disks. Domain decomposition methods/spectral element methods extend the applicability of spectral methods to more complex geometries. An alternative is to embed the irregular domain into a regular one. This paper uses the spectral method with domain embedding to solve PDEs on complex geometry. The running time of the new algorithm has the same order as that for the usual spectral collocation method for PDEs on regular geometry. The algorithm is extremely simple and can handle Dirichlet, Neumann boundary conditions as well as nonlinear equations.     

Development of PLGA-PEG-COOH and Gelatin-Based Microparticles Dual Delivery System and E-Beam Sterilization Effects for Controlled Release of BMP-2 and IGF-1

A poly(lactic-co-glycolic acid)-poly(ethylene glycol)-carboxyl (PLGA-PEG-COOH) and gelatin-based microparticles (MPs) dual delivery system for release of bone morphogenetic protein-2 (BMP-2) and insulin-like growth factor-1 (IGF-1) is developed. The delivery system is characterized based on its morphology, loading capacity, encapsulation efficiency, and release kinetics. The effects of electron beam (EB) sterilization on BMP-2 and IGF-1-loaded MPs and their biological effects are examined. The synergistic effect of a controlled dual release of BMP-2 and IGF-1 on osteogenesis of human mesenchymal stem cells (MSCs) is evaluated. Encapsulation efficiency of growth factors into gelatin and PLGA-PEG-COOH MPs is in the range of 64.78% to 76.11%. E-beam sterilized growth factor delivery systems are effective in significantly promoting osteogenesis of MSCs, although E-beam sterilization decreases the bioactivity of growth factors in MPs by ≈22%. BMP-2 release behavior from gelatin MPs/PEG hydrogel shows a faster release (52.7%) than that of IGF-1 from the PLGA-PEG-COOH MPs/PEG hydrogel (27.3%). The results demonstrate that the gelatin and PLGA-PEG-COOH MPs-based delivery system can realize temporal release of therapeutic biomolecules by incorporating different growth factors into distinct microparticles. EB sterilization is an accessible method for sterilizing growth factors-loaded carriers, which can pave the way for implementing growth factor delivery in clinical applications.     

Optimized Phase-Alternating Composite Pulse NMR

This paper describes phase-alternating composite pulse NMR by using computer optimizing method. The 180° n composite pulses, which are intensive in a wide range of resonance off-set (Δω/ω₁) variation, have been disigned. The theoretical results agreed with experimental data. This method may also be used to phase-unalternating pulses.     

A Phthalocyanine–Peptide Conjugate with High In Vitro Photodynamic Activity and Enhanced In Vivo Tumor‐Retention Property

A novel zinc(II) phthalocyanine conjugated with a short peptide with a nuclear localization sequence, Gly‐Gly‐Pro‐Lys‐Lys‐Lys‐Arg‐Lys‐Val, was synthesized by click chemistry and a standard Fmoc solid‐phase peptide synthesis protocol. The conjugate was purified by HPLC and characterized with UV/Vis and high‐resolution mass spectroscopic methods. Both this compound and its non‐peptide‐conjugated analogue are essentially non‐aggregated in N,N‐dimethylformamide and can generate singlet oxygen effectively with quantum yields (Φ_Δ) of 0.84 and 0.81, respectively, relative to unsubstituted zinc(II) phthalocyanine (Φ_Δ=0.56). Conjugation of the peptide sequence, however, can enhance the cellular uptake, efficiency in generating intracellular reactive oxygen species, and photocytotoxicity of the phthalocyanine‐based photosensitizer against HT29 human colorectal carcinoma cells. The IC₅₀ value of the conjugate is as low as 0.21 μM . In addition, the conjugate shows an enhanced tumor‐retention property in tumor‐bearing nude mice. After 72 h post‐injection, the dye concentration in the tumor was significantly higher than that in other organs. The results suggest that this phthalocyanine–peptide conjugate is a highly promising photosensitizer for photodynamic therapy.