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991.
Jeffries Thomas W. Yang Vina W. Davis Mark W. 《Applied biochemistry and biotechnology》1998,(1):257-265
Xylanases are commonly assayed by the dinitrosalicylic acid (DNS) or the arsenomolybdate (ARS) method. However, specific activities
are many times higher with DNS than with ARS. This is because the DNS assay is more reactive and the ARS assay is less reactive
with xylooligosaccharides than with xylose. Xylose is often used as a standard, even though oligosaccharides are prevalent,
so the DNS method overestimates and the ARS method underestimates specific activity. Ion chromatography, with pulsed amperometric
detection, separates and measures all products and intermediates, but quantitation on a molar basis is difficult, because
few xylooligosaccharide response factors are known. This report directly compares these three assay methods for the assay
of xylanase activities. 相似文献
992.
蚕沙叶绿素的降解及二氢卟吩e6醚衍生物的合成 总被引:7,自引:1,他引:7
研究了蚕沙叶绿素降解为二氢卟吩e6的化学过程, 并以二氢卟吩e6单甲酯为原料合成了九种二氢卟吩e6醚衍生物, 用UV/Vis、IR、^1H NMR及FAB-MS谱分别确定了它们的结构。 相似文献
993.
Araujo E Rodríguez-Malave AJ González AM Rojas OJ Peñaloza N Bullón J Lara MA Dmitrieva N 《Applied biochemistry and biotechnology》2002,97(2):91-103
In this work, the effect of Fento’s reagent on the degradation of residual Kraft black liquor was investigated. The effect
of Fenton’s reagent on the black liquor degradation was dependent on the concentration of H2O2. At low concentrations (5 and 15 mM) of H2O2, Fenton’s reagent caused the degradation of phenolic groups (6.8 and 44.8%, respectively), the reduction of reaction medium
pH (18.2%), and the polymerization of black liquor lignin. At a high concentration (60 mM) of H2O2, Fenton’s reagent induced an extensive degradation of lignin (95–100%) and discoloration of the black liquor. In the presence
of traces of iron, the addition of H2O2 alone induced mainly lignin fragmentation. In conclusion, Fenton’s reagent and H2O2 alone can degrade residual Kraft black liquor under acidic conditions at room temperature. 相似文献
994.
设计了一种新的Monte Carlo算法,在计算机上模拟了高分子链的超声裂解过程。首先根据Ovenall模型用遍历法对高分子链进行模拟断裂,随后进行倒接,进而反演了整个裂解过程。在获得大量模拟结果的基础上,分别研究了极限断裂次数的频率分布,最可几极限断裂次数与聚合度之间的关系,极限断片长度的平均分布,以及分子量多分散系数与裂解程度之间的关系。 相似文献
995.
Rui Ping QIAO Yong Min MA Xin Hua QI Nan LI Xiang Can JIN Qi Shan WANG Yuan Yi ZHUANG 《中国化学快报》2005,16(9):1271-1274
The experiments were performed to investigate the degradation of microcystins in order to assess the effectiveness and feasibility of UV/H2O2 system for the disinfection of water polluted by microcystins. The influence factors such as H2O2, pH and UV light intensities were investigated respectively. Degradation of microcystin-RR (MC-RR) could be fitted by either the pseudo-first-order or second-order rate equations. This homogenous system could significantly enhance the degradation rate due to the synergetic effect between UV and H2O2. The degradation mainly followed the mechanism of direct photolysis and .OH oxidation reactions. Experimental results showed that 94.83% of MC-RR was removed under optimal experimental conditions and the UV/H2O2 system provided an alternative to promote the removal of microcystins in drinking water supplies. 相似文献
996.
Yi-caiZhu Xiao-hongZhang Jin-liangQiao Gen-shuanWei 《高分子科学》2004,(2):147-154
Polydimethylsiloxane (PDMS) rubber latex with two sorts of sensitizers, trimethylol propane tri-methacrylate (TMPTMA) and diethylene glycol di-acrylate (DEGDA), was irradiated with y-rays and electron beams in various conditions. The radiation crosslinking reaction of PDMS occurs in the inner phase of the latex and is relatively isolated from the water phase. Therefore the oxygen and the radicals produced by the radiolysis reaction of water almost have no effect on the crosslinking reaction of polymer. The experimental data correspond with the Charlesby-Pinner relationship in the main. The gelation doses, degree of crosslinking and degradation as well as G values of crosslinking were calculated. From them, the sensitization coefficients were derived to offer a quantitative measurement of the enhancing effect of sensitizer on the radiation crosslinking. 相似文献
997.
Poly(?-caprolactone-co-β-butyrolactone) (PCLBL)-based polyurethane (PCLBL-PU) was synthesized and its tensile properties and hydrolytic degradability were investigated in an attempt to improve the degradability of poly(?-caprolactone)-based polyurethane (PCL-PU). PCLBL was synthesized by the ring-opening polymerization of ?-caprolactone (CL) and β-butyrolactone (BL) with stannous octoate as a catalyst. The introduction of a small amount of BL units significantly decreased the crystallinity of PCLBL. The crystallinity of the soft segment of PCLBL-PU also decreased with increasing BL content, and thus its hydrolytic degradation rate was dramatically increased. PCLBL-PU polymerized with PCLBL containing 5.7 mol% of BL units showed very similar tensile properties to PCL-PU, but its hydrolytic degradation rate increased by 100% at 45 °C. 相似文献
998.
硅橡胶热降解动力学的研究 总被引:5,自引:1,他引:5
用恒温热失重方法,研究了甲基硅橡胶(Si—O—1),用氢氧化钾催化聚合的甲基硅橡胶(Si—O—2),主链含环二硅氮烷的硅氮橡胶(Si—N—1)以及它与Si—O—1的共混物Si—O—3和与Si—O—2的共混物Si—O—4的热降解反应动力学.结果表明Si—N—1有最高的热稳定性,在氮气下,其降解反应活化能为344kJ/mol.并且发现它分别与Si—O—1和Si—O—2的共混物的热稳定性大幅度提高.Si—O—3在氮气下的降解活化能由未加入Si—N—1前的152kJ/mol提高到230kJ/mol;Si─O─4则由未混入Si─N─1前的61kJ/mol提高到144kJ/mol.我们认为这种作用机理是由于硅氮橡胶除去了微量吸附水和硅羟基并导致催化剂的离子对难于分离的结果. 相似文献
999.
生物可降解磷酸酯-碳酸酯共聚物的合成及性能研究 总被引:3,自引:0,他引:3
通过光气,二氯磷酸酯和双酚A反应,合成六种磷酸酯 碳酸酯共聚物,用IR、1H NMR及元素分析表征了共聚物,测量了Mn和热学性质.初步研究了在pH74磷酸盐缓冲溶液中,核糖核酸酶或碱性磷酸酶存在下的体外降解性能及其对抗肿瘤药物5 Fu的释放性能. 相似文献
1000.
J. J. Suñol J. Saurina F. Carrasco X. Colom F. Carrillo 《Journal of Thermal Analysis and Calorimetry》2007,87(1):41-44
Lyocell, modal and
viscose fibers were subjected to mercerization or to solar degradation. The
ulterior thermal degradation was analyzed by means of differential scanning
calorimetry (DSC). Thermal analysis shows wide exothermic processes that began
between 250 and 300°C corresponding to the main thermal degradation and
are associated to a depolymerization and decomposition of the regenerated
cellulose. Thermal degradation was analyzed as a function of concentration
and time. Lyocell fiber is the most stable under thermal degradation conditions.
Furthermore, mercerized samples are initially more degraded and present a
lower thermal stability. 相似文献