Influence of containing moisture on hydrothermal stability of modified collagen thermal characteristics analysis by DSC

The thermal stability of sheepskin collagen cross-linked with chrome sulfate and mimosa (MI)–oxazolidine (OZ), respectively, had been researched in this experiment. All samples’ shrinkage temperatures (T _s) are determined by a special T _s-testing-apparatus and denaturation temperatures (T _d) are determined by the differential scanning calorimetry. The relations between the modified collagens containing moisture and their hydrothermal stability, T _s or T _d, were studied. The results show that the cross linking agents can enhance the thermal stability of modified collagen whose T _s are 109.8 and 110.6 °C for collagen treated with chrome and MI–OZ, respectively. When the samples contain 25–71.9% moisture for chrome leather and 20–71.1% for leather treated with MI–OZ, the hydrothermal stability will decrease with the increase of moisture. It was found that the difference between T _s and T _d of collagen modified by chrome is more obvious than that of collagen modified with MI–OZ. And when the moisture of chrome leather exceeds 55%, T _d cannot express thermal stability of modified collagen as a substitute for T _s, and the moisture is 40% for leather tanned with MI–OZ.     

Amperometric sensing of dopamine using a single-walled carbon nanotube covalently attached to a conical glass micropore electrode

A single-walled carbon nanotube (SWNT) is covalently attached to the interior surface of a conical glass micropore electrode (GME) to create a novel amperometric dopamine sensor (SWNT/NH-GME). The SWNT/NH-GME combines the advantages of excellent transport properties of the cone-shaped micropore with the characteristics of a SWNT, exhibiting a dramatic electrocatalytic effect on the oxidation of dopamine (DA). Cyclic voltammetry and amperometric methods were employed to study the electrochemical behavior of the SWNT/NH-GME. The results showed that the SWNT/NH-GME sensor exhibited an excellent immunity from ascorbic acid interference and was able to measure DA concentrations with a detection limit of 4.2 × 10^?7 mol/L (S/N = 3).     

The immobilization of Cytochrome c on MWNT–PAMAM–Chit nanocomposite incorporated with DNA biocomposite film modified glassy carbon electrode for the determination of nitrite

A novel and sensitive biosensor was developed for the determination of nitrite. Firstly, multi-walled carbon nanotubes–poly(amidoamine)–chitosan (MWNT–PAMAM–Chit) nanocomposite along with the incorporation of DNA was used to modify the glassy carbon electrode. Then the immobilization of Cyt c was accomplished using electrochemical deposition method by consecutive cyclic voltammetry (CV) scanning in a neutral Cyt c solution. CV behaviors of the modified electrodes showed that the MWNT–PAMAM–Chit nanocomposite is a good platform for the immobilization of DNA and Cyt c in order, at the same time, an excellent promoter for the electron transfer between Cyt c and the electrode. At high potential, the immobilized Cyt c could be further oxidized into highly reactive Cyt c π-cation by two-step electrochemical oxidation, which could oxidize NO₂ ⁻ into NO₃ ⁻ in the solution. Therefore, a nitrite biosensor based on the biocatalytic oxidation of the immobilized Cyt c was fabricated, which showed a fast response to nitrite (less than 5 s). The linear range of 0.2–80 μM and a detection limit of 0.03 μM was obtained. Finally, the application in food analysis using sausage as testing samples was also investigated.     

Preparative separation of major xanthones from mangosteen pericarp using high‐performance centrifugal partition chromatography

Mangosteen fruit pericarp (MFP) is a rich source of xanthones, which has shown remarkable pharmacological activities. To isolate xanthones, previous methods included labor intensive and time‐consuming solid‐phase extractions (Sephadex LH20, silica gel) and sequential solvent extraction. In this study, major xanthones (α‐ and γ‐mangostins) in MFP were isolated at high purity in one step utilizing high‐performance centrifugal partition chromatography with solvent system composed of petroleum ether, ethyl acetate, methanol and water (10:5:5:1). In one run, 200 mg crude extract of MFP was injected and 55.4 mg α‐mangostin and 12.4 mg γ‐mangostin were obtained with the purity of 93.6 and 98.4%, respectively. The yields of them were 86.3 and 76.3%, respectively. As α‐ and γ‐mangostins are reported to show potent antioxidant, anti‐inflammatory and anticancer activities, this method can be used for the large‐scale production of them for future in vitro and in vivo biological studies.     

Chromatographic fingerprint study on Evodia rutaecarpa (Juss.) Benth by HPLC/DAD/ESI‐MSn technique

The LC–ESI‐MSⁿ method was developed for the analysis and characterization of alkaloids in the extract of E. rutaecarpa (called Wuzhuyu in Chinese). Thirty‐six batches of Wuzhuyu from different locations of China were investigated and the common fingerprinting profile was established with a professional analytical software recommended by the State Food and Drug Administration. Fifteen chemical components of the common peaks were identified by multi‐stage MS. The effects on the chromatographic profile resulting from different collecting locations, harvesting times or storage times were studied. Hierarchical clustering analysis and principal components analysis were also performed to classify and differentiate the 36 batches of the samples. As a result, those which had same chemical properties were sorted into one cluster, which was very useful in evaluating and controlling the quality of Wuzhuyu.     

LiCl-Promoted Pd(II)-catalyzed ortho carbonylation of N,N-dimethylbenzylamines

Palladium-catalyzed highly regioselective carbonylation of substituted N,N-dimethylbenzylamines with the assistance of LiCl was developed. The ortho-functionalized N,N-dimethylbenzylamine was further transformed into ortho-methyl benzoate under mild conditions. These two transformations could be combined into one pot to produce the desired product in moderate yield. Applications of this methodology to synthesize the fragments of variolaric acid were also studied.     

Determination of uric acid in human urine by capillary zone electrophoresis with indirect laser-induced fluorescence detection

A CZE with indirect LIF detection method was used for the determination of uric acid (UA) in human urine. UA and its coexisting analytes (i.e. hypoxanthine, xanthine and ascorbic acid) could be well separated within 4.5?min at a voltage of 25?kV with 25°C cartridge temperature in a running buffer composed of 5?mM sodium borate, 10% methanol (v/v) and 0.3?μM fluorescein sodium (apparent pH of the final mixed hydro-organic solution of sodium borate, methanol and fluorescein is 9.5). Under the optimum condition, the method has good linearity relationships (correlation coefficients: 0.9973-0.9987) with ranges of 25-500, 25-350, 25-250 and 25-300?μg/mL for hypoxanthine, ascorbic acid, xanthine and UA, respectively. The detection limits for the analytes were in the range of 0.29-0.90?μg/mL. The intra-day RSD values for migration times and peak areas were less than 0.43 and 3.27%, respectively. This method was applied to the quantitation of UA in human urine with recoveries in the range of 93.1-107.3%.     

Synthesis and crystal structures of two polymeric silver(I) complexes with polyamines and terephthalic acid

Two polymeric silver(I) complexes, [Ag₄(TAA)₂(TA)₂] · 2[Ag(TA)₂] (I) and [Ag₂(TA)(BA)] _n (II), where TAA is tris(2-aminoethyl)amine, TA is terephthalic acid, BA is butane-1,4-diamine, were synthesized and structurally characterized by elemental analyses and X-ray diffraction. Complex I consists of mononuclear [Ag(TA)₂] units and TA-bridged tetranuclear [Ag₄(TAA)₂(TA)₂] units, which are further linked via Ag…Ag interactions to form chains. In complex II, the silver atoms are linked by the TA and BA groups to form chains, which are further linked via Ag…Ag interactions to form layers. In both complexes, molecules are finally linked through intermolecular hydrogen bonds to form three-dimensional networks.