Viability of Bacteria in Hybrid Aqueous Silica Gels

Whole E. coli bacteria have been trapped within silica gels obtained via the acidification of sodium silicate and silica nanoparticles solutions. Their 7l147755/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-galactosidase enzymatic activity increases with time, suggesting that their membrane is partially lysed during the encapsulation process. Such a lysis can be greatly reduced when encapsulation is performed in the presence of gelatin. The biocatalytic activity of trapped bacteria remains almost constant for more than a week. Moreover bacteria trapped in such gels remain able to incorporate glucose, showing that their viability has been preserved.     

荧光法测定铍的研究

研究了新荧光试剂 7 [(2 ,4 二羟基 5 羧基苯 )偶氮 ] 8 羟基喹啉 5 磺酸 (DHCPAQS)与铍络合的反应条件及测定方法。在pH 8.0硼砂体系的缓冲介质中形成R∶Be =2∶1型的强荧光配合物 ,其λex/λem=362nm/ 497nm。铍含量在 0～ 0 .2 0mg·L- 1范围内呈线性关系 ,检出限为 2 .2×10 - 6 mol·L- 1。该方法应用于合金样中痕量铍的测定 ,结果满意。     

Stereoselective synthesis of Nuphar quinolizidine alkaloid, (−)-deoxynupharidine

A stereoselective synthetic route to Nuphar quinolizidine alkaloid, (−)-deoxynupharidine, was established by employing reductive carbon-nitrogen bond cleavage, followed by simultaneous recyclization of a proline derivative with samarium diiodide, and an intramolecular ring-closing metathesis, as the key steps.     

Efficient highly diastereoselective synthesis of 1,8a-dihydro-7H-imidazo[2,1-b][1,3]oxazines

1-Alkyl imidazoles react smoothly with dialkyl acetylenedicarboxylates in the presence of pyridine carboxaldehydes to diastereoselectively produce 1,8a-dihydro-7H-imidazo[2,1-b][1,3]oxazine derivatives in excellent yields.     

Structure–activity relationships of cannabinoids: A joint CoMFA and pseudoreceptor modelling study

A cannabinoid pseudoreceptor model for the CB1-receptor has been constructed for 31 cannabinoids using the molecular modelling software YAK. Additionally, two CoMFA studies were performed on these ligands, the first of which was conducted prior to the building of the pseudoreceptor. Its pharmacophore is identical with the initial superposition of ligands used for pseudoreceptor construction. In contrast, the ligand alignment for the second CoMFA study was taken directly from the final cannabinoid pseudoreceptor model. This altered alignment gives markedly improved cross-validated r² values as compared to those obtained from the original alignment with 782m7h872153047/10822_2004_Article_153516_TeX2GIFIE1.gif" alt=" $${\text{r}}_{{\text{cross}}}^2 $$ " align="middle" border="0"> values of 0.79 and 0.63, respectively, for five components. However, the pharmacophore alignment has the better predictive ability. Both the CoMFA and pseudoreceptor methods predict the free energy of binding of test ligands well.     

Materialersparnis,zeitgewinn und erhöhte genauigkeit in der massanalyse durch “umkehrtitrationen”

If, in volumetric analysis, the solution, as well as the reagent, is measured by means of a burette (replacing the usual pipette), we are able, after reaching the first end-point, to add a small quantity of either solution, substance or reagent, to titrate for a second end-point and to repeat these operations as many times as are necessary to obtain an average value with the desired accuracy, which 7;can be very high. The economy, both in tbc amount of solution required and time, is considerable. The procedure is very useful in theoretical .studies on controversial volumetric reactions and in calibrating burettes.     

Characterization of sixty alkenes in a cat-cracked gasoline naphtha by gas chromatography

Summary The alkene-rich petrol fraction from refinery fluid catalytic cracking (FCC) has been characterized by GC and GC-MS. Quantitative proportions and retention data of 52 acyclic and 11 cyclic C₅–C₇ alkenes are given. Relative retentions are reported for methylsilicone and aluminium oxide stationary phases as methylene units (MU). Applications of mass spectra, single-ion GC-MS monitoring and retention data for identifications are demonstrated.     

Die Kristallstrukturen von Me3SiI · β-Picolin und Me3SiI · γ-Picolin Vergleich der Lewis-Basen Pyridin, β-Picolin und γ-Picolin

The Crystal Structure of Me₃SiI · β-Picoline and Me₃SiI · γ-Picoline A Comparison between the Lewis-Bases Pyridine, β-Picoline, and γ-Picoline The reaction of Iodinetrimethylsilane with β- und γ-Picoline (Pic) leads to solid 1 : 1 compounds Me₃SiI · β-Picoline 1 , Me₃SiI · γ-Picoline 2. The reaction was performed at room temperature. Yellow single crystals were obtained by sublimation. Single crystal X-ray investigations confirm that both compounds are ionic [Me₃SiPic]⁺I^?. The comparison of β-Picoline with γ-Picoline and Pyridine (Py) demonstrates that the presence of a methyl group and also its position has no significant influence on the Si? N bond length in compound 1, 2 and on the adduct Me₃SiI · Py.     

邻硝基苯基荧光酮化学发光性能和机理研究

研究了在碱性介质中金属离子催化邻硝基苯基荧光酮（ｏ－ＮＰＦ）－Ｈ２Ｏ２体系的化学发光行为。结果表明，在研究的２０多种金属离子中，只有Ｃｏ２＋离子对ｏ－ＮＰＦ－Ｈ２Ｏ２体系有较强的催化发光作用，Ｃｏ２＋的浓度与发光强度在２．５×１０－９～３．０×１０－６ｇ／ｍＬ范围内呈良好的线性关系。通过对化学发光光谱、荧光光谱的研究以及用Ｈｕｃｋｅｌ分子轨道法（ＨＭＯ）计算了ｏ－ＮＰＦ的π电子分布和键级，提出了ｏ－ＮＰＦ可能的化学发光机理．     

Surface and fluorescence properties of a novel fluorescent surfactant

A novel kind of fluorescent surfactant having 7-hydroxylcoumarin group in the long alkyl chain was synthesized. The critical micelle concentration (CMC), surface tension (γ_cmc) at CMC and absorption, fluorescence properties of this product were determined. From the variations of fluorescence spectra in different solvents, it is observed that the polarity and dielectric constant of the solvents play important roles in the maximum fluorescence intensity and wavelength. Moreover, the surprised exhibition of two fluorescence bands in neutral and alkaline solutions has been attributed to the superexciplex formation of the product molecules. Also, the lower product concentration measuring the fluorescence properties as well as the supposed configuration of hydrogen bond of the product indicate that the larger aggregations cannot exist in alkaline solutions. The superexciplex is a possibility with two or more polar excited molecules together to form an excited state association.