Synthesis and screening of a molecularly imprinted polymer library targeted for penicillin G

A library of molecularly imprinted polymers (MIPs) was synthesized by radical bulk polymerization using the beta-lactam antibiotic penicillin G as the template. Diversity of the library was obtained by combining various functionalized monomers and cross-linkers and by varying the stoichiometry and the concentration of the components in the prepolymerization mixtures. The library was screened for selectivity to penicillin G by a radioligand binding assay and was compared to a corresponding control library. The best MIP candidate, showing the highest selectivity for penicillin G, was prepared from methacrylic acid and trimethylolpropane trimethacrylate as the functionalized monomer and cross-linker, respectively. Cross-reactivity studies with other beta-lactam antibiotics showed a low cross-reactivity of penicillin V (15%), ampicillin (16%), and amoxicillin (19%). Nafcillin and oxacillin showed less cross-reactivity (<1%). Cross-reaction with a cephalosporin antibiotic (cephapirin) and structurally nonrelated antibiotics (chloramphenicol, tetracycline, dapsone, and erythromycin) was less than 0.01%.     

Preconcentration and separation of copper(II), cadmium(II) and chromium(III) in a syringe filled with 3-aminopropyltriethoxysilane supported on silica gel

In this study, a syringe was filled with silica gel loaded with 3-aminopropyltriethoxysilane, for the separation and preconcentration of copper, cadmium and chromium prior to their determination by graphite furnace atomic absorption spectrometry (GFAAS) in seawater. For this purpose, a syringe was filled with 0.5 g of modified silica gel and the sample solution was drawn into the syringe and ejected back again. The analyte elements were quantitatively retained at pH 5. Then, the elements sorbed by the silica gel were eluted with 2.0 M of HCl and determined by GFAAS. At optimum conditions, the recovery of Cu, Cd and Cr were 96-98%. Detection limits (3delta) were 6.6, 7.5 and 6.0 micro g L(-1) for Cu, Cd and Cr, respectively. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only once. Cu, Cd and Cr added to a seawater sample were quantitatively recovered (>95%) in the range of the 95% confidence level. The method proposed in this paper was compared with a column technique. Optimum experimental conditions, reproducibility, precision and recoveries of both techniques are the same, but the syringe technique is much faster, easier and more practical than the column technique. It is a portable system and allows one to make the sorption process in the source of sample. In addition, the risk of contamination is less than in the column technique.     

Borate adsorption at Pt(111) in acidic medium

The adsorption/desorption process of borate was studied at Pt(111) in acidic solution by cyclic voltammetry. A so-called butterfly wave in the cyclic voltammogram of Pt(111) in HClO₄ shifted to negative direction upon the addition of boric acid with the disappearance of its sharp spikes. The shift in potential was found to be −57 mV with a tenfold increase of boric acid concentration. This illustrates that this anomalous wave is due to borate adsorption/desorption by a one-electron transfer process. The borate adsorption/desorption wave was observed to shift by −63 mV/pH. At pH>3, the anomalous wave splits forming two separate waves, depending on the pH and the scan rate. The appearance of two waves is assigned to the change in the adsorption mode of borate or the participation of OH in the adsorption process.     

Coordination of solvent molecules to VO(acac)<Subscript>2</Subscript> complexes in solution studied by hyperfine sublevel correlation spectroscopy and pulsed electron nuclear double resonance

Interactions and binding sites of the solvent molecules chloroform and ethanol to bis(acetylacetonate)oxovanadium(IV) (VO(acac)₂) complexes in (frozen) solutions have been investigated by pulsed electron nuclear double resonance, sum peak electron spin echo envelope modulation and hyperfine sublevel correlation spectroscopy. The experimental proton hyperfine coupling data of coordinating solvent molecules have been interpreted using quantum chemical calculations (density functional theory). Experimental and computed hyperfine couplings indicate that ethanol coordinates to vanadium in the equatorial plane of VO(acac)₂ and chloroform interacts via hydrogen bonding to oxygens of the acac ligands.     

Thermal stability of lysozyme and myoglobin in the presence of anionic surfactants

The interactions of lysozyme and myoglobin with anionic surfactants (hydrogenated and fluorinated), at surfactant concentrations below the critical micelle concentration, in aqueous solution were studied using spectroscopic techniques. The temperature conformational transition of globular proteins by anionic surfactants was analysed as a function of denaturant concentration through absorbance measurements at 280 nm. Changes in absorbance of protein-surfactant system with temperature were used to determine the unfolding thermodynamics parameters, melting temperature, T _m, enthalpy, ΔH _m, entropy, ΔS _m and the heat capacity change, ΔC _p, between the native and denatured states.     

排序集抽样下Inverse Rayleigh分布的Fisher信息量及其在参数估计中的应用

文章分别在简单随机抽样和排序集抽样下研究了Inverse Rayleigh分布中对应样本所含刻度参数θ的Fisher信息量.数值结果表示,同等样本容量的排序集样本比简单随机样本提供更多关于θ的信息.接着分别基于简单随机样本和排序集样本构造了θ的一些优良估计,并对估计结果进行了数值比较.     

CARRIER PHOTOGENERATION IN POLY（N-VINYL-CARBAZOLE）-BASED PHOTOCONDUCTIVE THIN-FILM DEVICES

In this paper, photoexcitation processes in the bilayer devices based on inorganic materials and poly（N-vinylcarbazole） （PVK） were investigated. In order to clarify the roles of inorganic materials in photoconductive properties of bilayer devices, TiO2 and ZnS were chosen to combine with PVK. A model for generation of photocurrent （Iph） in single layer device of PVK was obtained. It is deduced that the recombination rate constant （Pcomb） and the ionization rate constant （y） ofexcitons should be considered as the most important factors for Iph. For inorganic materials （TiO2 or ZnS）/PVK bilayer devices, in reverse bias of-4 V, the photocurrent of 115 mA/cm^2 in the TiO2/PVK device was observed, but the photocurrent in the ZnS/PVK device was only 10 mA/cma under the illumination light of 340 nm and the light intensity of 14.2 mW/cm^2. The weaker photocurrent is attributed to the absorption of ZnS within UV region and the energy offset at the interface between PVK and ZnS, which impedes the transport of charge carriers.     

Orientation control of perovskite thin films on glass substrates by the application of a seed layer prepared from oxide nanosheets

Orientation control of perovskite compounds was investigated by the application of a seed layer prepared from oxide nanosheets. An aqueous suspension of oxide nanosheets was prepared by the exfoliation of a layered compound of KCa₂Nb₃O₁₀ oxide grains. A seed layer composed of (TBA)Ca₂Nb₃O₁₀ nanosheets (TBA = tetrabutylammonium) was formed on a glass substrate by simply dip coating it in the suspension. Two kinds of perovskite compounds, LaNiO₃ (LNO) and Pb(Zr,Ti)O₃ (PZT) with a preferred orientation of (00l) were successfully grown on this seeded glass substrate. In this study, the relation between lattice mismatch and electrical properties is investigated. A large, oriented PZT film with a size of 5 ×4 cm shows an improved P-E hysteresis behavior by use of this orientation control.     

On the Sixth Power Mean of the Two-term Exponential Sums

Acta Mathematica Sinica, English Series - The main purpose of this article is to study the calculating problem of the sixth power mean of the two-term exponential sums, and give an interesting...     

Regularity of Viscosity Solutions of the Biased Infinity Laplacian Equation

In this paper, we are interested in the regularity estimates of the nonnegative viscosity super solution of the $β$−biased infinity Laplacian equation $$∆^β_∞u = 0,$$ where $β ∈ \mathbb{R}$ is a fixed constant and $∆^β_∞u := ∆^N_∞u + β|Du|,$ which arises from the random game named biased tug-of-war. By studying directly the $β$−biased infinity Laplacian equation, we construct the appropriate exponential cones as barrier functions to establish a key estimate. Based on this estimate, we obtain the Harnack inequality, Hopf boundary point lemma, Lipschitz estimate and the Liouville property etc.