柠檬酸铝/聚丙烯酰胺胶态分散凝胶反应动力学和机理的研究

采用粘度法研究了柠檬酸铝（AlCit)与部分水解取丙烯酰胺（HPAM）胶态分散凝胶体系的反应动力学。结果表明，胶态分散凝胶体系的交联反应是一级反应。并推导出胶态分散凝胶体系的反应动力学方程。     

On-surface isostructural transformation from a hydrogen-bonded network to a coordination network for tuning the pore size and guest recognition

Rational manipulation of supramolecular structures on surfaces is of great importance and challenging. We show that imidazole-based hydrogen-bonded networks on a metal surface can transform into an isostructural coordination network for facile tuning of the pore size and guest recognition behaviours. Deposition of triangular-shaped benzotrisimidazole (H₃btim) molecules on Au(111)/Ag(111) surfaces gives honeycomb networks linked by double N–H⋯N hydrogen bonds. While the H₃btim hydrogen-bonded networks on Au(111) evaporate above 453 K, those on Ag(111) transform into isostructural [Ag₃(btim)] coordination networks based on double N–Ag–N bonds at 423 K, by virtue of the unconventional metal–acid replacement reaction (Ag reduces H⁺). The transformation expands the pore diameter of the honeycomb networks from 3.8 Å to 6.9 Å, giving remarkably different host–guest recognition behaviours for fullerene and ferrocene molecules based on the size compatibility mechanism.

A hydrogen-bonded network on a Ag(111) surface can transform into an isostructural Ag(i) coordination network, giving drastically different host–guest recognition behaviours.     

Palladium‐Catalyzed Three‐Component Coupling Reaction of Allyl Carboxylates,Norbornenes and Diboronates Involving Sequential Olefins Insertion and Borylation Reaction

An efficient Pd‐catalyzed three‐component coupling reaction of allyl carboxylates, norbornenes and diboronates is described, which allows efficient assembly of C(sp³)—C(sp³) and C(sp³)—B bonds in a single process. Moreover, this approach shows advantages of good chemo‐ and regioselectivity, as well as good substrates suitability.     

Intriguing self-assembly of large granules of F-actin facilitated by gelsolin and alpha-actinin

We report microscopic observations and a structural determination of actin granules self-assembled in concentrated solutions of actin filaments (F-actin). Optical microscopy shows reproducible formation of numerous and stable granules of densely packed F-actin of variable sizes on the order of 10 microm. These granules coexist with a uniform network of F-actin of a lower concentration. The microscopic segregation of F-actin into two distinct states is assisted by an actin cross-linking protein, alpha-actinin. The rapid on and off rates and temperature sensitivity of the alpha-actinin/F-actin interaction facilitate the formation of multi-micrometer-sized granules of well-defined shapes. Additional physical factors such as the excluded volume effect and the minimization of surface energy act in concert with the specific molecular interactions to define the intriguing granular formation. Both the biochemical specificity of alpha-actinin and the thermodynamics of phase transitions are required for understanding such large scale self-assembly.     

Novel 99mTc labeled σ receptor ligand as a potential tumor imaging agent

A novel ^99mTc labeled complex, [N-[2-((2-oxo-2-(4-(3-phenylpropyl)piperazin-1-yl)ethyl) (2-mercaptoethyl)amino)acetyl]-2-aminoethanethiolato]Technetium(V) oxide (PPPE-MAMA’-^99mTcO) ([ ^99m Tc]-2) has been designed and prepared based on the integrated approach. The corresponding rhenium complex (PPPE-MAMA’-ReO)(Re-2) has been prepared and characterized. In vitro competition binding assays show moderate affinity of Re-2 towards σ₁ and σ₂ receptors with K _i values of 8.67 ± 0.07 and 5.71 ± 1.88 μmol, respectively. Planar images obtained at 0.5 h, 4 h, 20 h after i.v. injection indicate the accumulation of [ ^99m Tc]-2 in MCF-7 human breast tumor bearing mice at 20 h. Furthermore, the accumulation of [ ^99m Tc]-2 has been inhibited at 20 h after co-injection of [ ^99m Tc]-2 plus haloperidol (1 mg/kg). Biodistribution studies of [ ^99m Tc]-2 display an in vivo tumor uptake of 0.14% ± 0.01% ID/g at 24 h post i.v. injection with a tumor/muscle ratio of 6.02 ± 0.87. The above results suggest that [ ^99m Tc]-2, derived from a previously published lead compound, retains certain tumor uptake and affinity for σ receptors. [ ^99m Tc]-2 may be used as a basis for further structural modifications to develop tumor imaging agents with high affinity for σ receptors.     

226Ra and possible water contamination due to phosphate fertilizer production

The raw material used in the production of fetilizers is phosphate ore containing various amounts of naturally radioactive elements. During phosphate ore processing, owing to chemical properties of radium, practically all²²⁶Ra gets incorporated into phosphogypsum and becomes the main source of radioactivity. This study was carried out in a fertilizer factory in central Croatia, which may represent a site of significant environmental contamination due to fertilizer production and phosphogypsum deposition in the area. The purpose of this paper was to determine whether ingestion of drinking water in this area poses a health risk for the inhabitants. The results of our study confirmed the occurrence of²²⁶Ra in elevated concentrations in the samples of trickling waters. However, concurrent analyses of drinking water indicated that the risk of adverse health effects for the population living in the vicinity of a phosphate fertilizer plant is negligible.     

Indirect complexometric titration of potassium,rubidium, cesium,thallium and ammonium

A titrimetric method using EDTA for the determination of potassium, rubidium, cesium, thallium and ammonium has been developed. These cations are precipitated as M₂Ag[Co(NO₂)₆] and the blue cobalt thiocyanate complex in acetone-water mixed system is titrated with EDTA. Milligram quantities have been determined in the present work     

A highly sensitive assay for protein with dibromochloro-arsenazo-Al(3+) using resonance light scattering technique and its application

A simple, sensitive and selective method has been developed for the determination of protein using resonance light scattering (RLS) technique. The method is based on the interaction of protein and arsenazo-DBC-Al(3+) in the pH range of 5.0-7.0, which causes a substantial enhancement of the resonance scattering signal of arsenazo-DBC-Al(3+) in the wavelength range of 300-550 nm with the maximum RLS platform at 405-420 nm. With this method, 2.50-50.00 mug ml(-1) of bovine serum albumin (BSA) and 2.50-60.00 mug ml(-1) of human serum albumin (HSA) can be determined, and the detection limits, calculated three times the standard deviation (S.D.) of six blank measurements, for BSA and HSA were 123.4 and 89.6 ng ml(-1), respectively. Moreover, the method is free from interference from many amino acids and metal ions. The method, with high sensitivity, selectivity and reproducibility, was satisfactorily applied to the determination of total protein in human serum samples. Mechanism studies indicated that arsenazo-DBC-Al(3+) could bind to BSA depending mainly on electrostatic forces, which results in enhanced RLS in the arsenazo-DBC-Al(3+)-protein system.     

Highly efficient rhodium/monodentate phosphoramidite catalyst and its application in the enantioselective hydrogenation of enamides and alpha-dehydroamino acid derivatives

An easily prepared and highly efficient monodentate phosphoramidite ligand derived from BINOL, (S)-2,2'-O,O-(1,1'-binaphthyl)-dioxo-N,N-diethylphospholidine, was examined in the hydrogenation of both enamides and alpha-dehydroamino acid derivatives. The catalyst provided remarkably high enantioselectivities (up to 99.6% ee for enamides and >99.9% ee for alpha-dehydroamino acid derivatives).     

树枝状十二酯的合成

以乙二胺和丙烯酸十二酯为原料，甲醇为溶剂，采用迈克尔加成反应合成了低代的树枝状十二酯。探讨了反应条件对树枝状十二酯收率的影响。乙二胺2mL(30mmol)，n(乙二胺)：n(丙烯酸十二酯)=1：6，甲醇占反应液总体积的50％，反应温度40℃，反应时间48h，产率54．9％。