反相微乳液酶催化合成木质素-对甲酚共聚物

采用一种全新的反相微乳液体系 :十六烷基三甲基溴化铵 正丁醇 异辛烷 水 ,用辣根过氧化物酶催化合成木质素对甲酚共聚物 ,证实了反应的可行性。红外光谱的结果表明木质素与对甲酚发生了聚合反应 ,差示扫描量热分析的结果表明引入对甲酚改善了木质素的热性能。讨论了该聚合过程中酶浓度 ,活性剂浓度 ,W0 :c(H2 O) c(CTAB) ,酚浓度 ,木质素浓度 ,醇烃比对分子量的影响 .回归实验数据得出控制分子量大小的关联式 ,平均偏差为 8.7%。     

间苯二酚和3,5-二羟基苯甲酸共聚物的酶促合成与表征

在辣根过氧化物酶(HRP)/H2O2的催化体系下,间苯二酚(RSC)和3,5-二羟基苯甲酸(DBA)进行自由基聚合反应,制备了合成鞣剂。研究了单体配比以及反应各因素对共聚物性能的影响。结果表明,在间苯二酚和3,5-二羟基苯甲酸的摩尔配比为2∶1、反应温度为35℃、pH值为7.0、H2O2的滴加时间为90 min时,合成反应具有较高的产率。用红外光谱(FTIR)、核磁共振光谱(NMR)和凝胶渗透色谱(GPC)对聚合产物的结构和性能进行了表征。提出了RSC和DBA的自由基聚合反应机理。应用结果表明,聚合产物具有较好复鞣和助染性能。     

酶催化水溶性导电聚苯胺的模板导向合成与表征

对辣根过氧化物酶(HRP)催化水溶性导电聚苯胺的合成进行了研究.以聚乙烯磺酸钠(PVS)作为反应的聚阴离子模板.详细地研究了反应体系的pH值、H2O2浓度及苯胺与PVS的摩尔比对苯胺聚合的影响.用UV-vis-near-IR、FTIR及四探针电导率测试仪对产物进行了表征,并与其他模板聚合产物进行了比较.研究结果表明,PVS可作为HRP催化苯胺聚合的模板,合成的PVS/PANI的电导率为4.78×10-1S·cm-1,反应体系的pH值应控制在4.0～5.0,H2O2浓度以20 mmol·L-1为宜,PVS与苯胺的摩尔比应控制在1～1.5.     

氢供体组与辣根过氧化酶活性光谱研究

对邻苯二酚-苯胺和苯酚-氨基安替吡啉构成的两组测定HRP酶活性的体系进行了研究和比较。紫外可见光光谱和高效液相色谱分析表明,在HRP催化过程中,邻苯二酚-苯胺氢供体对会生成为一种粉红色产物,该产物最大吸收波长在510咖,可用于HRP的活性测量。且与常规使用的苯酚-氨基安替吡啉氢供体对的情况相比,具有更高的灵敏度、更低的检测限值和很好的重复性,在对HRP分别进行20次酶活测量,所得相对标准偏差仅为2．9％。使用邻苯二酚-苯胺氢供体对的方法可计算得到酶动力学参数Km（12．5mM）和Vmax（12．2mMmin^-1mg^-1）。     

辣根过氧化物酶在三种孔材料上的在线固定化研究

利用已建立的顺序注射紫外可见分析系统,以硅基介孔材料MCM-41、SBA-15和炭材料XC-72作为载体,研究和比较了辣根过氧化物酶(HRP)在3种无机孔材料上的在线吸附行为。结果表明,HRP在XC-72上的负载量和结合稳定性高于MCM-41和SBA-15,且以XC-72为载体制备的固定化HRP具有较高的活性和良好的操作稳定性。     

抗坏血酸诱导的玉米幼苗耐热性及其与抗坏血酸过氧化物酶的关系

外源抗坏血酸（AsA）预处理可显著增强玉米幼苗的耐热性。外源抗坏血酸预处理后,提高了玉米幼苗内源AsA含量和抗坏血酸过氧化物酶（APX）的活性,且外源AsA预处理过的幼苗在高温处理期间能保持相对较高的AsA含量和APX活力。     

Chloroplast Thylakoidal Ascorbate Peroxidase,PtotAPX, Has Enhanced Resistance to Oxidative Stress in Populus tomentosa

Chloroplasts are the most major producers of reactive oxygen species (ROS) during photosynthesis. However, the function of thylakoid ascorbate peroxidase (tAPX) in response to oxidative stress in wood trees is largely unknown. Our results showed that PtotAPX of Populus tomentosa could effectively utilize ascorbic acid (AsA) to hydrolyze hydrogen peroxide (H₂O₂) in vitro. The overexpression or antisense of PtotAPX (OX-PtotAPX or anti-PtotAPX, respectively) in Populus tomentosa plants did not significantly affect plant morphology during plant growth. When treated with methyl viologen (MV), the OX-PtotAPX plants exhibited less morphological damage under stress conditions compared to WT plants. OX-PtotAPX plants maintained lower H₂O₂ levels and malondialdehyde (MDA) contents, but more reduced AsA levels, a higher photosynthetic rate (Pn), and the maximal photochemical efficiency of PSII (Fv/Fm), whereas anti-PtotAPX plants showed the opposite phenotype. Furthermore, the activity of APX was slightly higher in OX-PtotAPX under normal growth conditions, and this activity significantly decreased after stress treatment, which was the lowest in anti-P. Based on these results, we propose that PtotAPX is important for protecting the photosynthetic machinery under severe oxidative stress conditions in P. tomentosa, and is a potential genetic resource for regulating the stress tolerance of woody plants.     

Effect of dietary selenium on the progression of heart failure in the ageing spontaneously hypertensive rat

Oxidative stress has been directly implicated in hypertension and myocardial remodelling, two pathologies fundamental to the development of chronic heart failure. Selenium (Se) can act directly and indirectly as an antioxidant and a lowered Se status leads to a higher risk of cardiovascular disease. This study examined the role of Se on the development of hypertension and subsequent progression to chronic heart failure in spontaneously hypertensive rats (SHR). Three dietary groups were studied: (i) Se‐free; (ii) normal Se (50 μg Se/kg food); and (iii) high Se (1000 μg Se/kg food). Systolic blood pressure and echocardiography were used to detect cardiac changes in vivo. At study end, cardiac tissues were assayed for glutathione peroxidase activity, thioredoxin reductase activity, and protein carbonyls. The major finding of this study was the high heart failure‐related mortality rate in SHRs fed an Se‐free diet (70%). Normal and high levels of dietary Se resulted in higher survival rates of 78 and 100%, respectively. Furthermore, high dietary Se was clearly associated with lower levels of cardiac oxidative damage and increased antioxidant expression, as well as a reduction in disease severity and mortality in the SHR.     

Stabilization of oil-in-water emulsions by enzyme catalyzed oxidative gelation of sugar beet pectin

Enzyme catalyzed oxidative cross-linking of feruloyl groups can promote gelation of sugar beet pectin (SBP). It is uncertain how the enzyme kinetics of this cross-linking reaction are affected in emulsion systems and whether the gelation affects emulsion stability. In this study, SBP (2.5% w/v) was mixed into an oil-in-water emulsion system (4.4% w/w oil, 0.22% w/w whey protein, pH 4.5). Two separate, identically composed, emulsion systems were prepared by different methods of preparation. The emulsions prepared separately and subsequently mixed with SBP (referred as Mix A) produced significantly larger average particle sizes than the emulsions in which the SBP was homogenized into the emulsion system during emulsion preparation (referred as Mix B). Mix B type emulsions were stable. Enzyme catalyzed oxidative gelation of SBP helped stabilize the emulsions in Mix A. The kinetics of the enzyme catalyzed oxidative gelation of SBP was evaluated by small angle oscillatory measurements for horseradish peroxidase (HRP) (EC 1.11.1.7) and laccase (EC 1.10.3.2) catalysis, respectively. HRP catalyzed gelation rates, determined from the slopes of the increase of elastic modulus (G′) with time, were higher (P < 0.05) than the corresponding laccase catalyzed rates, but the final G′ values were higher for laccase catalyzed gels, regardless of the presence of emulsions or type of emulsion preparation (Mix A or Mix B). For both enzymes, rates of gelation in Mix A were higher (P < 0.05) than in Mix B, and higher stress was needed to break the gels in Mix A than in Mix B at similar enzyme dosage levels. These differences may be related to a lower availability of the feruloyl groups for cross-linking when the SBP was homogenized into the emulsion system during preparation.