Analysis for Flavonoids in Bee Pollens by Capillary Electrophoresis

A capillary electrophoresis (CE) method has been developed for the determination of six bioactive flavonoids that are commonly found in health foods: hesperidin, hyperin, isorhamnetin, kaempferol, quercetin and rutin. The effects of several parameters, such as pH, buffer concentration, separation voltage and UV detector wavelength, were investigated to find the optimal conditions. Using a HbBCh-NaiB-iO? buffer (pH 9.2), the analytes can be separated within 8 min. The relative standard deviations of migration times in eight injections were between 0.77% and 0.93%, and those of the peak areas ranged from 3.8% to 8.6%. A high reproducibility and excellent linearity was observed over two orders of magnitude, with detection limits (S/N = 3) ranging from 0.34ug ml to 2.9ug ml for all the six analytes. Recoveries ranged from 80.4 % to 113.9 %. The new method is simple, reproducible and sensitive. No solid phase extraction for sample pretreatment is necessary. Analysis results are accurate in application to bee pollens.

不同海拔珠芽蓼抗氧化系统的研究

对生长在青藏高原不同海拔地区的多年生高山植物珠芽蓼(Polygonum viviparum L．)的抗氧化系统进行了测试，以探讨高山植物对于高寒环境的适应机理．结果表明：随着海拔的升高，叶绿素a(chla)、叶绿素b(chlb)含量明显下降，chla／chlb增大，珠芽蓼叶和根细胞的膜脂过氧化均加剧，丙二醛(MDA)含量明显增加．3种抗氧化酶的活性受到明显影响，其中叶片中过氧化物酶(POD)和超氧化物歧化酶(SOD)活性，随海拔升高而活性降低，而均与根中的变化趋势相反．过氧化氢酶(CAT)活性随海拔升高呈增强的趋势，且叶片中活性较根中变化明显．抗坏血酸(ASA)随海拔的升高，含量呈明显增加．膜脂过氧化与抗氧化物酶的变化具有不一致性，这可能表明两种抗氧化系统之间存在一定的协同作用，特别是高含量的抗坏血酸，可能在高山植物适应高寒环境的胁迫方面具有更加重要的作用．图5表1参22

青藏高原不同海拔矮蒿草抗氧化系统的比较

对生长在青藏高原不同海拔自然生境下的多年生典型抗寒植物－矮蒿草（Kobresia humilis）的抗氧化系统进行了比较研究。结果表明，矮蒿草的叶组织中，非酶抗氧化系统物质脯氨酸（Pro）和抗坏血酸（AsA），随着海拔升高具有明显的增加趋势。在抗氧化酶系统中，过氧化物酶（POD）和过氧化氢酶（CAT）活性均随海拔的升高，而明显增强。但叶中的超氧化物歧化酶（SOD），随着海拔的升高，其活性有下降趋势，三者变化趋势并不一致。高海拔矮蒿草的植株与低海拔的植株相比，叶细胞内的膜脂过氧化加剧，丙二醛（MDA）含量明显增。细胞可溶性蛋白也随海拔升高显著增加。根中的抗氧化系统变化与叶中的有所不同。根中AsA含量随海拔而显著升高，且较叶中的增加明显，但Pro含量则有所减少。根中的CAT和POD活性变化与叶中的变化趋势基本一致，且随海拔高度的增加，根中的CAT活性较叶中的变化更为明显。而根中的SOD活性变化不如叶中明显，MDA含量随海拔增高，其变化趋势比叶中的小。可见，青藏高原典型抗寒植物矮蒿草体内的两类抗氧化系统，在不同海拔条件下可能存在互补协同的调节作用，这可能是矮蒿草适应或抵抗高原极端高寒低温和强UV－B辐射等环境胁迫的重要生理机制之一。

Characterization of polyethylene glycol-modified proteins by semi-aqueous capillary electrophoresis

A new program to characterize polyethylene glycol-modified (PEGylated) proteins is outlined using capillary zone electrophoresis (CZE). PEGylated ribonuclease A and lysozyme were selected as examples. Five separation procedures were compared to select out the mixed buffer of acetonitrile-water (1:1, v/v) at pH 2.5 as the best to characterize the PEGylated proteins without sample pretreatment. Polyethylene oxide (PEO) with a high molecular mass of 8X10(6) was applied to rinse the capillary to form a dynamic coating which would decrease the undesirable proteins adsorbed to the inner wall of the silica. The electroosmotic flow (EOF) mobility of the five procedures was determined, respectively. It is found that acetonitrile is mainly responsible for the good resolution of PEGylated proteins with the help of PEO coating in the semi-aqueous system. The low EOF mobility and current in the semi-aqueous system might also have some responsibility for the high resolution. The semi-aqueous procedure described in this paper also demonstrates higher resolution of natural proteins than aqueous ones. (C) 2001 Elsevier Science B.V. All rights reserved.

NMR study on the acidity of TS-1 zeolite

The acidic properties of TS-1 and Silicalite-I zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the P-31 MAS NMR and H-1 MAS NMR techniques with trimethylphosphine, not only Bronsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more acidic compared with Silicalite-1. The H-1, Si-29 MAS NMR spectra and the resonance related to Bronsted acid species in the P-31 MAS NMR spectra demonstrate clearly that the presence of titanium in the framework results in the formation of a new hydroxy group, titanols, which is more acidic than silanols of Silicalite-1. The P-31 MAS NMR measurements also illustrate convincingly the existence of at least two different Lewis acid species on the TS-1 zeolites. The conversion of propylene oxide into methoxypropanol catalyzed by TS-1 or Silicalite-I zeolite in methanol solution as a test reaction has also been described. With the increase of titanium in zeolite, TS-1 appears to have a higher activity during the reaction of propylene oxide to methoxypropanol.

Comparative study by infrared spectroscopy and microcalorimetry of the CO adsorption over supported palladium catalysts

The adsorption of CO on Al(2)O(3), ZrO(2), ZrO(2)-SiO(2), and ZrO(2)-La(2)O(3) supported Pd catalysts was studied by adsorption microcalorimetry and infrared (TR) spectroscopy. Some interesting and new correlations between the results of microcalorimetry and IR spectroscopy have been found. The CO is adsorbed on palladium catalysts in three different modes: multibonded (3-fold), bridged (2-fold), both on Pd(lll) and (100) planes, and linear (1-fold) adsorbed species. The corresponding differential adsorption heats lie in the field of high (210-170 kJ/mol), medium (140-120 kJ/mol), and low (95-60 kJ/mol) values, respectively. The nature of the support, the reduction temperature, and the pretreatment conditions affect the surface structure of the Pd catalysts, resulting in variations in the site energy distribution, i.e., changes in the fraction of sites adsorbing CO with specific heats of adsorption. Moreover, the CeO(2); promoter addition weakens the adsorption strength of CO on palladium. Based on the exposed results, a correctness factor, which considers the percentages of various CO adsorption states, must be introduced when one calculates the Pd dispersion using CO adsorption data.

A high-resolution solid-state NMR study on nano-structured HZSM-5 zeolite

Variations in the structure and acidity properties of HZSM-5 zeolites with reduction in crystal sizes down to nanoscale (less than 100 nm) have been investigated by XRD, TEM and solid-state NMR with a system capable of in situ sample pretreatment. As evidenced by a combination of Al-27 MAS NMR, Si-29 MAS, CP/MAS NMR and H-1 MAS NMR techniques, the downsize of the zeolite crystal leads to an obvious line broadening of the Al-27, Si-29 MAS NMR spectrum, an increasing of the silanol concentration on the external surface, and a pronounced alteration of the acidity distribution between the external and internal surfaces of the zeolite. In a HZSM-5 zeolite with an average size at about 70 nm, the nonacidic hydroxyl groups (silanols) are about 14% with respect to the total amount of Si, while only 4% of such hydroxyl groups exist in the same kind of zeolite at 1000 nm crystal size. The result of H-1 MAS NMR obtained using Fluorinert(R) FC-43 (perfluorotributyl amine) as a probe molecule demonstrates that most of the silanols are located on the external surface of the zeolite. Moreover, the concentration of Bronsted acid sites on the external surface of the nano-structured zeolite appears to be distinctly higher than that of the microsized zeolite.

Epoxidation of cyclohexene on Ti/SiO2 catalysts prepared by chemical grafting TiCl4 on deboronated silica xerogel

Ti/SiO2 (or Ti/de[B]SiO2) catalysts were prepared by grafting deboronated silica xerogel with gaseous TiCl4. Using TBHP as oxidant, the Ti/de[B]SiO2 catalyst shows both catalytic activity and selectivity in epoxidation of cyclohexene better than 80%, and the activity can be comparable with that of Ti-beta. The catalytic activity of Ti/de[B]SiO2 strongly depends on the content of B of support precursor, and the pretreatment temperature of the support. IR studies show that the sites in the deboronated silica xerogel to react with TiCl4 are not only the silanol nests, but also the defect sites produced during the deboronation. (C) 2001 Elsevier Science B.V. All rights reserved.

Determination of total iron binding capacity of serum by capillary electrophoresis

A capillary electrophoresis (CE) technique for determining total iron binding capacity (TIBC) of serum has been developed. The optimum serum pretreatment involves the following major steps: at first, saturate serum transferrin with Fe+3; then, dissociate them completely after removing excess unbound Fe. Finally, complex the released iron with phenanthroline, a chromophore, to make suitable for the CE analysis. Ammonium acetate (pH = 5.0) was used as CE background electrolyte solution. In this system, a good linear correlation coefficient was maintained over the range 0.5 similar to 10 mu M (r = 0.9979, n =12). Seven adult serum samples were studied and the TIBC parameters measured. In the present system, 10 similar to 30 mu L serum is sufficient for determination. The study shows that the CE technique described is a powerful method for rapid, efficient, sensitive and reliable analysis and hence particularly suitable for clinical application.

Bilirubin-human serum albumin interaction monitored by capillary zone electrophoresis

Capillary zone electrophoresis was used to monitor the interaction between bilirubin and human serum albumin. Cord blood serum samples were injected directly into an uncoated fused-silica capillary (30 cm x 50 mu m i.d.) and separation was accomplished within 4 min without extensive sample pretreatment. The most suitable running buffer to separate free bilirubin from albumin bound bilirubin was found to contain 1.0 mmol/L EDTA, 5% acetonitrile and 15 mmol/L phosphate with pH adjusted to 8.4. Approximately two bilirubin dianions could be bound per human serum albumin molecule in the cord blood serum. The binding constant was estimated to be 1.1 x 10(5) (L/mol) at 25 degrees C and pH 8.4. The peak area ratio of free bilirubin to total bilirubin can be used to determine the bilirubin binding capacity of cord blood serum for the concentration range of total bilirubin from 204 to 340 mu mol/L using 1:5 diluted cord blood seras. Copyright (C) 1999 John Wiley & Sons, Ltd.

Simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene over dimolybdenum nitride catalysts

A series of unsupported dimolybdenum nitride (gamma-Mo(2)N) catalysts differing in surface area were prepared by temperature programmed reduction of MoO(3) with a mixture of NH(3):N(2) (90:10). Characterization of catalysts by BET, XRD, TPR and XPS techniques was carried out. The samples were used as catalysts in hydrotreating reactions (simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene). Low surface area gamma-Mo(2)N materials show much higher specific conversions than those with higher surface area. These results indicate that HDS and HYD reactions over gamma-Mo(2)N seem to be structure-sensitive. The relative exposure extent of crystalline planes (111) and (200) over the different catalysts can be associated with their hydrogen adsorption capacities and with their catalytic performances. The catalytic activities are significantly affected by the catalyst pretreatment conditions. (C) 1999 Elsevier Science B.V. All rights reserved.

吗啡奖赏效应及其敏化与空间学习能力的关系

Rewarding experience after drug use is one of the mechanisms of substance abuse. Previous evidence indicated that rewarding experience was closely related to learning processes. Neuroscience studies have already established multiple-mode learning model. Reference memory system and habit memory are associated with hippocampus and dorsa striatum respectively, which are also involved in the rewarding effect of morphine. However, the relationship between spatial/habit learning and morphine reward property is still unclear. After drug use, with sensitization to rewarding effect, spatial learning is also changed. To study the mechanism of increment of spatial learning would provide new perspective about reward learning. Based on the individual difference between spatial learning and reward learning, the experiments studied relationship between the two leaning abilities and tested the function of dorsal hippocampus and dorsal striatum in morphine-induced CPP. The results were summarized below： 1 In a single－rule learning water maze task, subjects better in spatial learning also excelled in rewarding learning. In a multi-rule learning task, morphine administration was more rewarding to subjects of use place strategy. 2 Treatment potentiating the rewarding effect of morphine also increased place-rule learning, with no significant improvement in habit learning. 3 Intracranial injections into CA1 of hippocampus or dorsal striatum of M1 antagonist, Pirenzepine, could block the establishment of morphine CPP after three days morphine treatment. In contrast, the antagonist of D1 receptor SCH23390 had no blocking effect. Both Pirenzepine and SCH23390 blocked the locomotor-stimulating effect of morphine. In summary, spatial learning stimulated the behavioral expression of morphine’s rewarding effect, in which CA1 of hippocampus was critically involved. On the other side, a pretreatment schedule of morphine, while increased the rewarding effect, improved place-rule learning, indicating that spatial learning might be one chain of sensitization to drug rewards effects

XRD and XPS studies on the ultra-uniform Raney-Ni catalyst prepared from the melt-quenching alloy

We present a novel method for preparing an ultra-uniform Raney-Ni catalyst, which includes melt-quenching, hydrogen treatment and leaching in an alkali solution. The resultant catalyst shows superior activity in the reaction of cyclohexanone hydrogenation. X-ray diffraction (XRD) and XPS have been employed to characterize the catalysts. As demonstrated, the pretreatment with hydrogen caused a distinct phase transfer of the Ni-Al alloys, forming more of the Ni2Al3 component. In the subsequent leaching process, the Ni2Al3 component shows high activity and the resultant catalyst exhibits high surface areas and small pores. Moreover, metallic Al in the hydrogen-pretreated alloy appeared to be leached more easily and thus the aluminium species remaining on the catalyst surface is aluminium oxide predominantly, which serves as a matrix to stabilize active Ni species on the surface. Copyright (C) 2001 John Wiley & Sons, Ltd.

Low-temperature oxidation of CO over Pd/CeO2-TiO2 catalysts with different pretreatments

A comprehensive study of the low-temperature oxidation of CO was conducted over Pd/TiO2, Pd/CeO2, and Pd/CeO2-TiO2 pretreated by a series of calcination and reduction processes. The catalysts were characterized by N-2 adsorption, XRD, H-2 chemisorption, and diffuse-reflectance infrared Fourier transform spectroscopy. The results indicated that Pd/CeO2-TiO2 has the highest activity among these catalysts, whether in the calcined state or in the reduced state. The activity of all of the catalysts can be improved significantly by the pre-reduction, and it seems that the reduction at low temperature (LTR. 150 degrees C) is more effective than that at high temperature (HTR, 500 degrees C), especially for Pd/CeO2 and Pd/TiO2. The catalysts with various supports and pretreatments are also different in the reaction mechanisms for CO oxidation at low temperature. Over Pd/TiO2, the reaction may proceed through a surface reaction between the weakly adsorbed CO and oxygen (Langmuir-Hinshelwood). For Ce-containing catalysts, however, an alteration of reaction mechanism with temperature and the involvement of the oxygen activation at different sites were observed, and the light-off profiles of the calcined Pd/CeO2 and Pd/CeOi-TiO2 show a distortion before CO conversion achieves 100%. At low temperature, CO oxidation proceeds mainly via the reaction between the adsorbed CO on Pd-0 sites and the lattice oxygen of surface CeO2 at the Pd-Ce interface, whereas at high temperature it proceeds via the reaction between the adsorbed CO and oxygen. The high activity of Pd/CeO2-TiO2 for the low-temperature CO oxidation was probably due to the enhancements of both CO activation, caused by the facilitated reduction of Pd2+ to Pd-0, and oxygen activation, through the improvement of the surface oxygen supply and the oxygen vacancies formation. The reduction pretreatment enhances metal-support interactions and oxygen vacancy formation and hence improves the activity of CO oxidation. (c) 2005 Elsevier Inc. All rights reserved.

The formation of Co2C species in activated carbon supported cobalt-based catalysts and its impact on Fischer-Tropsch reaction

The cobalt carbide (Co2C) species was formed in some activated carbon supported cobalt-based (Co/AC) catalysts during the activation of catalysts. It was found that the activity of Fischer-Tropsch reaction over Co-based catalysts decreased due to the formation of cobalt carbide species. Some promoters and pretreatment of activated carbon with steam could restrain the formation of cobalt carbide.