苏云金芽胞杆菌含不同质粒和不同基因工程菌的生长代谢

用微量热法研究了世界上产量最大的微生物杀中心剂苏云芽胞杆菌(Bacillusthuringiensis)野生菌株YBT－1463,无晶体突变株BMB160和无质粒、无晶体突变株BMB171以及含量不同杀虫蛋白基因工程菌BMB－304－171－A和BMB－304－171－B的生长代谢动力学变化。结果是,含有14个质粒的野生菌株YBT－1463的生长代谢热比无晶体含6个质粒的变株BMB160和无晶体、无质粒突变株BMB171低;将杀虫晶体蛋白基因vryⅠAc和cryⅠC分别转入受体菌BMB171中后,两个工程菌BMB－303－171－A和BMB－304－171－B生长代谢热与受体菌BMB171相比也吸显降低;表明质粒形成一个耗能过程,当受体菌BMB171转入杀虫晶体蛋白基因后,工菌比受茶杯菌的放热大幅度减少,表明基因编码杀虫晶体蛋白也是一个耗能过程,但是含基因cryⅠAc和cryⅠC工程菌BMB－304－171－A和BMB－304－171－B之间的生长代谢没有明显差异。首次报道这些热动力学变化,对杀虫剂发酵生产过程的代谢控有重要指导意义。     

重组质粒对大肠杆菌HB101生长影响的微量热研究

用微量热方法研究了嗜麦芽假单胞菌AT18, 受体菌大肠杆菌HB101, mel基因工程菌——大肠杆菌HB101/pWSY8和携带克隆载体pUC18质粒的大肠杆菌HB101等的生长代谢过程. 实验结果从热化学和热动力学上阐明了细菌的生长速率常数与其所含质粒的大小呈负相关. 探讨了低温处理对含不同质粒大肠杆菌生长的影响, 发现低温处理对工程菌生长影响最大.     

极端嗜盐古生菌启动子序列缺失突变的微量热研究

用微量热方法和DNA缺失突变技术研究了来源于极端嗜盐古生菌R1上的一个推测的启动子片段(RM10)在大肠杆菌中的启动子功能. 启动子片段融合到质粒pKK232-8上无启动子的氯霉素乙酰转移酶(CAT)基因前来检测它驱动基因表达的能力, 缺失分析RM10启动子片段定位具有启动活性的重要功能区. 实验结果从热动力学角度揭示, 这个启动子片段上含有－35区和－10区特征的1382～1517 bp(碱基对)区段是它在大肠杆菌中具有启动子功能的关键部分; 在1～1382 bp区段或1571～1848 bp区段上还存在它的负调控区. 该研究为基因启动子功能研究提供了一种新的、更加灵敏便捷的、化学与生物学相结合的方法.     

Isolated peptidoglycan glycosyltransferases from different organisms produce different glycan chain lengths

Peptidoglycan is an essential component of bacterial cell wall. The glycan strands of peptidoglycan are synthesized by enzymes called peptidoglycan glycosyltransferases (PGTs). Using a high-resolution SDS-PAGE assay, we compared the glycan strand lengths of four different PGTs from three different organisms (Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus). We report that each enzyme makes a polymer having an intrinsic characteristic length that is independent of the enzyme:substrate ratio. The glycan strand lengths vary considerably, depending on the enzyme. These results indicate that each enzyme must have some mechanism, as yet unknown, for controlling product length. The observation that different PGTs produce different length glycan chains may have implications for their cellular roles and for the three-dimensional structure of bacterial peptidoglycan.     

A field theoretical description of states with different orbitals for different spins

A field theoretical formulation is given for the method of different orbitals for different spins (DODS ). For an infinite system DODS describes an antiferromagnetic state and to account for this spin ordering a Gorkov-type of factorization is introduced. A corresponding gap equation is derived, where a non-zero solution indicates the presence of long-range order in the system. Actually the formulation given is general enough as to render DODS as a special case. As shown, we may also obtain a ferrimagnetic as well as a density wave state solution depending on the special characteristics of the system at hand. A related type of antiferromagnetism is described by the Overhauser spin density wave (SDW ) state and also this theory is formulated in a field theoretical language. The similarities and differences between DODS and SDW are discussed. The energy expressions for the two states are given within the Hartree-Fock approximation. It is proposed that the SDW state could be used to partly account for the correlation problem in molecules, as well as the method of DODS which has previously been employed for that purpose.     

Grafting of montmorillonite with different functional silanes via two different reaction systems

Silane grafted montmorillonites were synthesized by using 3-aminopropyltriethoxysilane and trimethylchlorosilane via two different grafting reaction systems: (a) ethanol-water mixture and (b) vapor of silane. The resulting products were investigated using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA). XRD patterns demonstrate that silane was intercalated into the montmorillonite gallery, as indicated by the increase of the basal spacing. The product prepared by vapor deposition has a larger basal spacing than that obtained from solution, due to the different extent of silane hydrolysis in various grafting systems. TGA curves indicate that the methyl groups penetrate into the siloxane clay are the primary reason for the decrease of the dehydroxylation temperature of the grafted products. 3-Aminopropyltriethoxysilane in the grafted montmorillonite adopts a bilayer arrangement while trimethylchlorosilane adopts a monolayer arrangement within the clay gallery.     

Extinction coefficient of gold nanoparticles with different sizes and different capping ligands

Extinction coefficients of gold nanoparticles with core size ranging from approximately 4 to 40 nm were determined by high resolution transmission electron microscopy analysis and UV-vis absorption spectroscopic measurement. Three different types of gold nanoparticles were prepared and studied: citrate-stabilized nanoparticles in five different sizes; oleylamide-protected gold nanoparticles with a core diameter of 8 nm, and a decanethiol-protected nanoparticle with a diameter of around 4 nm. A linear relationship between the logarithms of extinction coefficients and core diameters of gold particles was found independent of the capping ligands on the particle surface and the solvents used to dissolve the nanoparticles. This linear relation may be used as a calibration curve to determine the concentration or average size of an unknown nanoparticle or nanoparticle-biomolecule conjugate sample.     

Analysis of alkaloids from different chemical groups by different liquid chromatography methods

Alkaloids are biologically active compounds widely used as pharmaceuticals and synthesised as secondary methabolites in plants. Many of these compounds are strongly toxic. Therefore, they are often subject of scientific interests and analysis. Since alkaloids — basic compounds appear in aqueous solutions as ionized and unionized forms, they are difficult for chromatographic separation for peak tailing, poor systems efficiency, poor separation and poor column-to-column reproducibility. For this reason it is necessity searching of more suitable chromatographic systems for analysis of the compounds.     

Three tetracyclic dibenzoazepine derivatives exhibiting different molecular conformations,different patterns of intermolecular hydrogen bonding and different modes of supramolecular aggregation

The biological potential of compounds of the tricyclic dibenzo[b ,e ]azepine system has resulted in considerable synthetic efforts to develop efficient methods for the synthesis of new derivatives of this kind. (9RS ,15RS )‐9‐Ethyl‐11‐methyl‐9,13b‐dihydrodibenzo[c ,f ]thiazolo[3,2‐a ]azepin‐3(2H )‐one, C₁₉H₁₉NOS, (I), crystallizes as a kryptoracemate with Z ′ = 2 in the space group P 2₁, with one molecule each of the (9R ,15R ) and (9S ,15S ) configurations in the asymmetric unit, while (9RS ,15RS )‐9‐ethyl‐7,12‐dimethyl‐9,13b‐dihydrodibenzo[c ,f ]thiazolo[3,2‐a ]azepin‐3(2H )‐one, C₂₀H₂₁NOS, (II), crystallizes with Z ′ = 1 in the space group C 2/c . Ethyl (13RS )‐2‐chloro‐13‐ethyl‐4‐oxo‐8,13‐dihydro‐4H‐benzo[5,6]azepino[3,2,1‐ij ]quinoline‐5‐carboxylate, C₂₂H₂₀ClNO₃, (III), exhibits enantiomeric disorder in the space group P such that the reference site is occupied by the 13R and 13S enantiomers, with occupancies of 0.900 (6) and 0.100 (6). In each of the two independent molecules in (I), the five‐membered ring adopts an envelope conformation, but the corresponding ring in (II) adopts a half‐chair conformation, while the six‐membered ring in the major form of (III) adopts a twist‐boat conformation. The conformation of the seven‐membered ring in each of (I), (II) and the major form of (III) approximates to the twist‐boat form. The molecules of compound (I) are linked by two C—H…O hydrogen bonds to form two independent antiparallel C (5) chains, with each type containing only one enantiomer. These chains are linked into sheets by two C—H…π(arene) hydrogen bonds, in which the two donors are both provided by the (9R ,15R ) enantiomer and the two acceptor arene rings form part of a molecule of (9S ,15S ) configuration, precluding any additional crystallographic symmetry. The molecules of compound (II) are linked by inversion‐related C—H…π(arene) hydrogen bonds to form isolated cyclic centrosymmetric dimers. The molecules of compound (III) are linked into cyclic centrosymmetric dimers by C—H…O hydrogen bonds and these dimers are linked into chains by a π–π stacking interaction. Comparisons are made with some related structures.     

Small can be different

Theoretical investigations of size evolutionary patterns for multiply charged anionic metal clusters and solvation of sodium in water clusters are discussed. For Na _N ^Z- clusters, energetic stability and electron decay channels are determined. Formation of a “surface Rydberg-like state” in Na(H₂O) _N , correlating with calculated and measured ionization potentials, is analyzed.     

Photoactive dimesogen having different pathways of light driven phase transitions at different temperatures

We hereby describe a novel example of light driven phase transitions in a photoresponsive dimesogen, which goes through different pathways at different temperatures. The isomer ratios required to obtain the phase transition in each case have also been determined.     

Synthesis and different molecular recognition of two dye-modified cyclodextrins with spacer of different length

Two β-cyclodextrin derivatives (1 and 2) bearing a hydroxyazobenzene unit, each having a butylene or a 4,7-dioxadecylene spacer between the cyclodextrin and the dye, were prepared, which showed guest-induced color changes with a marked difference in molecular recognition behavior in aqueous solution.