高碘酸钠氧化法测定肌醇含量

高碘酸钠氧化法测定肌醇含量张楚富，林清华，梁会（武汉大学生命科学学院武汉４３００７２）王泽胜（湖南兰龙科技实业公司长沙４１０００６）关键词植酸钙，肌醇，高碘酸钠氧化法分类号Ｑ５０８肌醇是一种环己六醇，它以植酸盐的形式主要存在于米糠和其他油料作物种子中...     

电光晶体补偿位相测量微小位移及其应用

介绍一种应用电光晶体补偿位相测量微小位移的方法,着重分析其测量精度,并应用这种方法校正压电陶瓷的线性,精度优于1%波长。     

Microwave-assisted synthesis utilizing supported reagents: a rapid and efficient acylation procedure

[reaction: see text] The application of microwave heating to a polymer-assisted solution-phase (PASP) synthesis technique has been utilized to develop a rapid and efficient protocol for the solution-phase synthesis of amides from either amine or carboxylic acid cores.     

The effect of bromine substitution on the charge-transfer emission of the complex of phenanthrene and tetracyanobenzene

The absorption spectra of the charge-transfer complexes of sym-tetracyanobenzene (TCNB) with phenanthrene, 9-bromophenanthrene, and 9,10-dibromophenanthrene are measured in chloroform solutions at room temperature. The total emission and phosphorescence spectra of the donors and the complexes are measured at 77 K in rigid glasses. The phosphorescence decay lifetimes are determined for phenanthrene, TCNB, and for the phenanthrene-TCNB complex, and a decrease in the phenanthrene-TCNB complex lifetime relative to the lifetimes of the two components is observed. The luminescence spectra of the complexes exhibit both a red shift and a lack of structure as compared with the donor spectra. The results are interpreted, in agreement with the results of Iwata et al. for the phenanthrene-TCNB complex (1), as an indication that there is a considerable degree of charge-transfer character in the lowest triplet state (T₁). Bromine substitution leads to a decrease in the energy of the phenanthrene triplet state. As a result, the energy gap between the donor molecule triplet state and the complex charge-transfer triplet state decreases from phenanthrene, to 9-bromophenanthrene, to 9,10-dibromophenanthrene. The results suggest that the proximity of these two triplet states in 9,10-dibromophenanthrene and its charge-transfer complex leads to some local donor triplet state character in the emitting complex triplet state.     

Carbon-13, proton spin–spin coupling constants in some 2-substituted propanes

Carbon-13, proton coupling constants have been measured in eighteen different 2-substituted propanes. ¹J(C-2,H) shows variations similar to those observed previously for monosubstituted methanes. ²J(C-2,H) is essentially independent of the substituent at C-2, while ²J(C-1,H) varies over a range of at least 5 Hz. The latter coupling constant becomes more positive as the electronegativity of the substituent increases while ³J(CH) decreases as the electronegativity of the substituent increases. The observed trends in ⁿJ(CH) are compared with those calculated using semi-empirical molecular orbital theory at the INDO level of approximation.     

Analysis of biomass sugars using a novel HPLC method

The precise quantitative analysis of biomass sugars is a very important step in the conversion of biomass feedstocks to fuels and chemicals. However, the most accurate method of biomass sugar analysis is based on the gas chromatography analysis of derivatized sugars either as alditol acetates or trimethylsilanes. The derivatization method is time consuming but the alternative high-performance liquid chromatography (HPLC) method cannot resolve most sugars found in biomass hydrolysates. We have demonstrated for the first time that by careful manipulation of the HPLC mobile phase, biomass monomeric sugars (arabinose, xylose, fructose, glucose, mannose, and galactose) can be analyzed quantitatively and there is excellent baseline resolution of all the sugars. This method was demonstrated for standard sugars, pretreated corn stover liquid and solid fractions. Our method can also be used to analyze dimeric sugars (cellobiose and sucrose).     

Calmodulin-mediated reversible immobilization of enzymes

This work demonstrates the use of the protein calmodulin, CaM, as an affinity tag for the reversible immobilization of enzymes on surfaces. Our strategy takes advantage of the of the reversible, calcium-mediated binding of CaM to its ligand phenothiazine and of the ability to produce fusion proteins between CaM and a variety of enzymes to reversibly immobilize enzymes in an oriented fashion to different surfaces. Specifically, we employed two different enzymes, organophosphorus hydrolase (OPH) and beta-lactamase and two different solid supports, a silica surface and cellulose membrane modified by covalently attaching a phenothiazine ligand, to demonstrate the versatility of our immobilization method. Fusion proteins between CaM-OPH and CaM-beta-lactamase were prepared by using genetic engineering strategies to introduce the calmodulin tail at the N-terminus of each of the two enzymes. In the presence of Ca(2+), CaM adopts a conformation that favors interaction between hydrophobic pockets in CaM and phenothiazine, while in the presence of a Ca(2+)-chelating agent such as EGTA, the interaction between CaM and phenothiazine is disrupted, thus allowing for removal of the CaM-fusion protein from the surface under mild conditions. CaM also acts as a spacer molecule, orienting the enzyme away from the surface and toward the solution, which minimizes enzyme interactions with the immobilization surface. Since the method is based on the highly selective binding of CaM to its phenothiazine ligand, and this is covalently immobilized on the surface, the method does not suffer from ligand leaching nor from interference from other proteins present in the cell extract. An additional advantage lies in that the support can be regenerated by passing through EGTA, and then reused for the immobilization of the same or, if desired, a different enzyme. Using a fusion protein approach for immobilization purposes avoids the use of harsh conditions in the immobilization and/or regeneration steps, which could cause inactivation of the immobilized enzyme. Moreover, we have demonstrated that the CaM affinity tag allows immobilization of enzymes on a variety of surfaces without compromising their enzymatic activity substantially; for example, the immobilized OPH retained more than 80% of the activity of the free enzyme. Our results with beta-lactamase showed the feasibility of using a phenothiazine surface in several consecutive loading and regeneration cycles. This can be advantageous when expensive and/or difficult to obtain immobilization surfaces have to be employed; the immobilization surface could be reused to immobilize the same or a different enzyme using the CaM affinity tail. We also determined that the phenothiazine-modified silica particles are stable for long periods of time, i.e., up to 2 years when stored at 4 degrees C. It is envisioned that this type of reversible immobilization may find applications in the development of reversible, reusable biosensors and bioreactors endowed with the additional advantage that the biological element at the surface of the sensor or bioreactor could be replaced under mild conditions when needed to sense or process a different target molecule.