Activity Gel Analysis of Endopeptidases in Rose Petals

Poor resolution for the identification of endopeptidase(EP) activity in activity gel assays is a critical issue in the analysis of the postharvest physiology of rose petals. In this paper, major factors influencing EP activity gel assays were evaluated. The results showed that a phosphate(NaH_2PO_4/Na_2HPO_4) buffer favors the detection of clear EP bands, as compared to Tris–HCl buffer. Removal of salts and pigments with Sephadex G-25 columns was vital to the measurement of EP activity in rose petal extracts. For optimal resolution of bands, we show that before electrophoresis,samples should be treated for 10 min at 40 °C. Additionally, electrophoresis should be done in 12% SDS–PAGE co-polymerized with 0.15%(w/v) gelatin. After electrophoresis, the optimal incubation temperature and pH are 42 °C and 7.0, respectively. Using our optimized assay, Rh-EP1,Rh-EP2, Rh-EP3, three proteases with molecular masses of 200, 123.5, and 97.4 kD, respectively, were detected in rose petals. Experiments using EP class-specific inhibitors revealed that Rh-EP2 and Rh-EP3 were both serine proteases, while Rh-EP1 was a metalloprotease. In this study, we also measured changes in EP activity during flower opening, senescence, and water deficit stress(WDS) using our optimized activity gel assay,and found that Rh-EP3 may be more relevant to senescence in roses compared with Rh-EP1 or Rh-EP2. Changes occurring to EPs after WDS were similar to those during the period from flower opening to senescence, and Rh-EP3 activities were greatly increased by WDS treatment. Collectively, our results suggest that significant increases in Rh-EPs activities, especially increases in Rh-EP3 activity, may contribute to the flower senescence induced under WDS treatment.

Determination of Trace Non Rare Earth Elements in High Purity Rare Earth Oxides by ICP－AES with Microcolumn Preconcentration in a Flow Injection System

A new method for the determination of trace non-rare earth elements in high purity rare earth oxides by ICP-AES with preconcentration on an active carbon-silica gel microcolumn in a flow injection system is described in this paper. Experimental parameters such as pH, flow rate,reagent concentration,length of reaction coil,eluent acidity,etc. were optimized. In the buffer solution of NH3. H2O/NH4Cl at pH 4. 6,Al,Cr,Cu,Fe, Pb, V and Zn can be preconcentrated and then eluted with 4. 5 mol/L nitric acid utilizing stop-flow technique. The enrichment factors were in range of 8. 1￣12. 6 with detection limits of μg/m level ,and the RSD with metals at μg/g level were 2. 3￣5. 0% (n= 7). The method proposed can reduce the matrix interference effectively , and has been applied to the determination of non-rare earth metals atμg/g level in high purity Eu2O3 with satisfactory results.

Adsorption of phenylalanine from aqueous solution onto active carbon and silica gel

The adsorption isotherms of phenylalanine from aqueous solution on active carbon and silica gel at varying pH,and the influence of inorganic salt upon the ad rption have been studied (at 25℃).The adsorption amount of phcnylalanine on the silica gel is very low due to the strong ad- sorption of water by silica gel.The results on the active carbon show:(1)The adsorption is found to be pH-dependent,within pH 4.1—5.1 it increases with pH,within pH 5.1—11.8 it decreases with pH,at pH 5.1 the adsorption reaches its maximum;(2)The phenylalanine is adsorbed mainly in the form of zwitterion;(3)A certain amount of cations and anions of phenylalanine are also adsorbed with van der Waals interaction;(4)After adding NaCl,the adsorption of phenylalanine increases markedly.

Vanadium-Doped Magnesium Oxide Nanoparticles Formation in Presence of Ionic Liquids and Their Use in Photocatalytic Degradation of Methylene Blue

Magnesium oxide（MgO） is one of the metal oxides having unique properties with numerous potential industrial applications.In this study,MgO and vanadium-doped MgO nanoparticles were synthesized by sol–gel method in 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF_4] and 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF_4] ionic liquids.Vanadium-doped MgO nanoparticles exhibited nanosphere and nanorod morphologies with 40–80 nm in particle size,primarily due to the influence of ionic liquids as demonstrated by high-resolution scanning electron microscopy and transmission electron microscopy.Characteristics of nanoparticles were also studied by thermal gravimetric analysis,X-ray diffraction and energy-dispersive X-ray spectroscopy.Photodegradation ability of synthesized nanoparticles was evaluated for methylene blue（MB） in specially designed UV reactor.Photodegradation is found to be dependent on doping,and particle characteristics change due to the influence of ionic liquid.The ionic liquid-assisted vanadium-doped MgO nanoparticles showed good reusability under UV irradiation and MB degradation ability under visible light.