Absorption and emission spectroscopic characterisation of combined wildtype LOV1-LOV2 domain of phot from Chlamydomonas reinhardtii

An absorption and emission spectroscopic characterisation of the combined wild-type LOV1-LOV2 domain string (abbreviated LOV1/2) of phot from the green alga Chlamydomonas reinhardtii is carried out at pH 8. A LOV1/2-MBP fusion protein (MBP=maltose binding protein) and LOV1/2 with a His-tag at the C-terminus (LOV1/2-His) expressed in an Escherichia coli strain are investigated. Blue-light photo-excitation generates a non-fluorescent intermediate photoproduct (flavin-C(4a)-cysteinyl adduct with absorption peak at 390 nm). The photo-cycle dynamics is studied by dark-state absorption and fluorescence measurement, by following the temporal absorption and emission changes under blue and violet light exposure, and by measuring the temporal absorption and fluorescence recovery after light exposure. The fluorescence quantum yield, phi(F), of the dark adapted samples is phi(F)(LOV1/2-His) approximately 0.15 and phi(F)(LOV1/2-MBP) approximately 0.17. A bi-exponential absorption recovery after light exposure with a fast (in the several 10-s range) and a slow component (in the near 10-min range) are resolved. The quantum yield of photo-adduct formation, phi(Ad), is extracted from excitation intensity dependent absorption measurements. It decreases somewhat with rising excitation intensity. The behaviour of the combined wildtype LOV1-LOV2 double domains is compared with the behaviour of the separate LOV1 and LOV2 domains.     

Recoverable solution reaction of HiPco carbon nanotubes with hydrogen peroxide

There is increasing interest in developing single-walled carbon nanotubes (SWNTs)-based optical biosensors for remote or in vitro and in vivo sensing because the near-IR optical properties of SWNTs are very sensitive to surrounding environmental changes. Many enzyme-catalyzed reactions yield hydrogen peroxide (H(2)O(2)) as a product. To our knowledge, there is no report on the interaction of H(2)O(2) with SWNTs from the optical sensing point of view. Here, we study the reaction of H(2)O(2) with an aqueous suspension of water-soluble (ws) HiPco SWNTs encased in the surfactant sodium dodecyl sulfate (SDS). The SWNTs are optically sensitive to hydrogen peroxide in pH 6.0 buffer solutions through suppression of the near-IR absorption band intensity. Interestingly, the suppressed spectral intensity of the nanotubes recovers by increasing the pH, by decomposing the H(2)O(2) into H(2)O and O(2) with the enzyme catalase, and by dialytically removing H(2)O(2). Preliminary studies on the mechanisms suggest that H(2)O(2) withdraws electrons from the SWNT valence band by charge transfer, which suppresses the nanotube spectral intensity. The findings suggest possible enzyme-assisted molecular recognition applications by selective optical detection of biological species whose enzyme-catalyzed products include hydrogen peroxide.     

实验室废液的回收及效果评价——以“铬废液回收及评价”为例

This paper introduces an experiment about waste liquid recovery and effect evaluation in laboratory. Through this experiment, the basic operations of crystal preparation, chemical analysis and instrumental analysis are further consolidated. At the same time, it allows students to experience a series of possible problems of condition selection and control in the process of waste liquid treatment. We hope to improve the students' ability to analyze and solve problems, enhance their interest in learning, and strengthen their humanistic education.     

In vivo near-infrared Raman spectroscopy: demonstration of feasibility during clinical gastrointestinal endoscopy

Raman spectroscopy (RS) has potential for disease classification within the gastrointestinal tract (GI). A near-infrared (NIR) fiber-optic RS system has been developed previously. This study reports the first in vivo Raman spectra of human gastrointestinal tissues measured during routine clinical endoscopy. This was achieved by using this system with a fiber-optic probe that was passed through the endoscope instrument channel and placed in contact with the tissue surface. Spectra could be obtained with good signal-to-noise ratio in 5 s. The effects on the spectra of varying the pressure of the probe tip on the tissue and of the probe-tissue angle were determined and shown to be insignificant. The limited set of spectra from normal and diseased tissues revealed only subtle differences. Therefore, powerful spectral-sorting algorithms, successfully implemented in prior ex vivo studies, are required to realize the full diagnostic potential of RS for tissue classification in the GI.     

新型光学活性α-氨基磷酸及其酯合成进展

α-氨基膦酸酯是一类很重要的天然氨基酸类似物，具有新颖的化学结构和多 种生理活性。综述了近年来光学活性α-氨基膦酸及酯的合成进展。     

New Host Molecules with Imidazoliums as Functional Arms:Syntheses and Anion Recognition

The bridged tri-imidazoliums 3.3X^--5.3X^-(X^-=PF6^-,Br^-,I^-)and bis-imidazoliums 6.2PF6^- were synthesized by N-quaternization of imidazole derivative 1 in acetonitrile under reflux.UV spectroscopic titration experiments showed that the halide salts and hexafluorophosphate salts of these imidazoliums exhibited good recognition toward anions in water and in acetonitrile,respectively.     

环氧丙烯酸酯的紫外光固化

制备了适于配制紫外光固化涂料的环氧丙烯酸酯，研究了反应温度、阻聚剂、催化剂等因素对环氧树脂与丙烯酸反应的影响；讨论了反应机理和动力学；并利用红外光谱观察了产物的紫外光固化行为。季铵盐能有效地催化环氧树脂和丙烯酸的反应，当其用量为０．６％～１．２％时，在９０～１１０℃反应４．５～８小时后，环氧基转化率大于９７％。由此配制的光固化涂料经紫外光辐照能快速固化。     

A theoretical study of electronic excited states of photosynthetic reaction center in Rhodopseudomonas viridis

The electronic singlet vertical excited states of photosynthetic reaction center (PSRC) in Rhodopseudomonas (Rps.) viridis were investigated by ZINDO and INDO/S methods. The effects of the interactions of pigment-pigment and pigment-protein on the electronic excitations were examined. The calculation results showed that the interactions of pigment-pigment and pigment-protein play an important role in reasonably assigning the experimental absorption and circular dichroism (CD) spectra of PSRC in Rps. virids. By comparing the theoretically computed excited states with the experimental absorption and CD spectra, satisfactory assignments of the experimental spectroscopic peaks were achieved.     

Angular hydroxymethyl directed intramolecular Diels-Alder approach for the stereo- and regioselective synthesis of pimaraditerpenes

The stereo- and regioselective synthetic route to pimaraditerpenes, employing an angular hydroxymethyl directed intramolecular Diels-Alder reaction of the decaline intermediate, has been developed. This synthetic approach allows prompt access to both natural pimaraditerpenes and the unnatural regioisomers, which would be potentially new anti-inflammatory pimaraditerpenes.     

Comparison of one-, two-, and three-dimensional iron phosphates containing ethylenediamine

A new two-dimensional (2d) iron phosphate, (C₂N₂H₁₀)Fe₂O(PO₄)₂, has been synthesized under hydrothermal conditions in the system of FeCl₃-H₃PO₄-C₂N₂H₈-H₂O. The crystal data is: space group P2₁/c, a=10.670(1) Å, b=10.897(1) Å, c=9.918(1) Å, β=105.632(1)°, Z=4. The layered structure consists of double sheet layers, of composition Fe₂O(PO₄)₂, built from FeO₅ trigonal bipyramids and PO₄ tetrahedra. The amine holds the layers together via H-bonding. The study of the magnetic properties reveals two magnetic transitions at 160 and 30 K with spin-glass-like behavior below 160 K. By varying the hydrothermal conditions, three other iron phosphates were synthesized: the one-dimensional (1d) (C₂N₂H₁₀)Fe(HPO₄)₂(OH)·H₂O, the 2d (C₂N₂H₁₀)Fe₂(PO₄)₂(OH)₂, and the three-dimensional (3d) (C₂N₂H₁₀)₂Fe₄O(PO₄)₄·H₂O. The 1d compound can be used as the starting reagent in the synthesis of both the 2d compound and the 3d lipscombite Fe₃(PO₄)₂(OH)₂ due to the similar building blocks in their structures. In the 3d phosphate (C₂N₂H₁₀)₂Fe₄O(PO₄)₄·H₂O, manganese can substitute for half of the iron atoms. Magnetic study shows ordering transitions at about 30 K, however, manganese substitution depresses the magnetic ordering temperature.