Microcalorimetric Evaluation of the Effect of Kanamycin： An Analysis Based on the Median-Effect Principle

A study of the effect of drug, kanamycin, on the growth metabolism of recombinant Escherichia coli B 1 was carded out by microcalorimeter monitoring of the metabolic activity of treated cells. Power-time curves of growing recombinant Escherichia coli cell suspensions, treated with different kanamycin doses, were recorded. The extent of the effect was evaluated by changes in the slopes of the microcalorimetric curves and the kinetics of the drug action was interpreted from the time at which these changes reached their maximum values and maintained their maximum values. Experimental dose-effect relationships conform to the median-effect principle of the mass-action law： fa/（1-fa）=（D/D50）^m. A plot of y=lg[（fa）^1-1]^-1 versus x=lg D gives the slope m, D50 and R∞. The experimental results revealed that high concentration of kanamycin had an inhibitory effect on the growth of recombinant Escherichia coli B 1 in the lg phase, and had a promoting effect in the stationary period. Moreover, it was demonstrated that microcalorimetry was a reliable method for the detection of modulatory effects in biology.     

PKU-5: an aluminoborate with novel octahedral framework topology

A new anhydrous aluminoborate Al4B6O15 (PKU-5) has been synthesized in a boric acid flux in a closed system at 350 degrees C. PKU-5, which crystallizes in the space group R3 with the lattice constants a=11.43398(9) and c=6.48307(5) A, consists of Al octahedra and triangularly coordinated boron. The Al octahedron adopts the (10,3)-a network, in which each octahedron shares three edges with the neighboring octahedra forming ten-membered-ring channels. The octahedral backbone in PKU-5 can be considered as a primary octahedral framework topology and, setting out from the structures of the aluminoborates (PKU-1 and PKU-5), we propose construction rules for the octahedral frameworks. There are two types of connections for edge-sharing octahedra in porous frameworks, trans and cis type, by which various microporous octahedral frameworks of different topologies can be constructed. The borate groups share oxygens with the Al octahedral frameworks forming two kinds of three-membered-ring units consisting of two octahedra and one triangle (2Al+B) and one octahedron and two triangles (Al+2B), respectively.     

alpha,5-didehydro-3-picoline diradicals from skipped azaenediynes: computational and trapping studies of an aza-Myers-Saito cyclization

[reaction: see text] On the basis of density functional calculations, the isomerization of skipped azaenediynes (C-alkynyl-N-propargylimines) to azaenyne allenes and subsequent rapid aza-Myers-Saito cyclization to alpha,5-didehydro-3-picoline were predicted. We prepared the N-propargylimine of 1-phenyl-3-tri(isopropyl)silylprop-2-yn-1-one, which undergoes proto-desilylation and isomerization to an azaenyne allene when treated with tetrabutylammonium fluoride. In the presence of 1,4-cyclohexadiene, this azaenyne allene affords 6-phenyl-3-picoline and other products corresponding to the trapping of an alpha,5-didehydro-3-picoline diradical.     

Li2O-TiO2-SiO2-P2O5和Li2O-TiO2-Al2O3-P2O5体系锂离子固体电解质的制备及性能研究

一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…     

A Novel Functionalized Single‐Wall Carbon Nanotube Modified Electrode and Its Application in Determination of Dopamine and Uric Acid in the Presence of High Concentrations of Ascorbic Acid

Multilayer films of negatively charged single‐wall carbon nanotubes (SWCNTs) and positively charged cetylpyridinium bromide (CPB) have been deposited on a glassy carbon electrode (GCE) using layer‐by‐layer (LBL) technique. The assembled multilayer films have been investigated by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance (QCM) measurements. The voltammetric signal of dopamine (DA), uric acid (UA), and ascorbic acid (AA) could be observed well‐separated with the assembled SWCNTs/CPB multilayer films in pH 7.0 PBS. The oxidation peak potentials of DA, UA, and AA are centered at about 169 mV, 292 mV and ?10 mV on differential pulse voltammograms (DPVs), respectively. The peak‐to‐peak potential separation was 123 mV, 179 mV, and 302 mV for DA‐UA, DA‐AA, and UA‐AA in DPVs, respectively. This permits the simultaneous detection of DA and UA in the presence of AA.     

Ion-transport and diffusion coefficients of non-plasticised methacrylic-acrylic ion-selective membranes

The ion-transport behaviour of methacrylic-acrylic-based polymers for ion-selective electrode (ISE) membranes was investigated by a spectrophotometric method to determine the apparent diffusion coefficient. By observing the degree of deprotonation of the chromoionophore or chromogenic ionophore, the extent of penetration of cations into the polymer films was determined. The transport of the cations into the optode films depended on the stoichiometry of complexation by the ionophores. The apparent diffusion coefficients, estimated from the deprotonation data were of the order of 10⁻¹² to 10⁻¹¹ cm² s⁻¹. These values indicate that the apparent ion mobility in the methacrylic-acrylic ISE membranes is approximately a thousand times lower than that in plasticised PVC ISE membranes. For some ionophores, the value of the apparent diffusion coefficient could be modulated according to the ionophore content in the membrane and the data obtained for a calixarene containing membrane were tested against a model for facilitated diffusion with chained carriers. The data did not fit a model where intramolecular diffusion was limiting, but were consistent with a first-order rate-limiting mechanism involving an intermediate 1:2 complex between ion and ionophore. In this instance, the lowest values for D_app were thus not necessarily obtained for lowest ionophore loading and in the range examined, a trend of decreasing D_app with increasing ionophore was noted.     

A new 5α,8α-epidioxysterol with immunosuppressive activity from the South China Sea soft coral Sinularia sp.

Abstract

A new 5α,8α-epidioxysterol, namely yalongsterol A (1), along with two known related steroids 5α,8α-epidioxy-24-methyl-cholesta-6,24(28)-dien-3β-ol (2) and (22E,24S)-5α,8α-epidioxy-24-methyl-cholesta-6,22-dien-3β-ol (3), were isolated from the South China Sea soft coral Sinularia sp. Their structures were established by extensive spectroscopic analyses and comparisons of the spectral data with those reported in the literature. In bioassay, compounds 1–3 showed moderate immunosuppressive activities against T and/or B lymphocyte cells with IC₅₀ values ranging from 19.30 to 59.49 μM, and low cytotoxicity on murine splenocytes with CC₅₀ values ranging from 40.88 to 62.29 μM.

     

Over one century after discovery: pyrylium salt chemistry emerging as a powerful approach for the construction of complex macrocycles and metallo-supramolecules

Over one century after its discovery, pyrylium salt chemistry has been extensively applied in preparing light emitters, photocatalysts, and sensitizers. In most of these studies, pyrylium salts acted as versatile precursors for the preparation of small molecules (such as furan, pyridines, phosphines, pyridinium salts, thiopyryliums and betaine dyes) and poly(pyridinium salt)s. In recent decades, pyrylium salt chemistry has emerged as a powerful approach for constructing complex macrocycles and metallo-supramolecules. In this perspective, we attempt to summarize the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry. We believe that this perspective not only highlights the recent achievements in pyrylium salt chemistry, but also inspires us to revisit this chemistry to design and construct macrocycles and metallo-supramolecules with increasing complexity and desired function.

This perspective summarizes the representative efforts of synthesizing and self-assembling large, complex architectures using pyrylium salt chemistry.     

MCuB7O12.nH2O (M = Na, K ): a new copper borate with 14-ring channels

The title compounds, which were synthesized in boric acid flux under mild conditions (493 K), contain a 14-member ring borate framework consisting of octahedral (CuO6), tetrahedral (BO4) and triangular (BO3) units.