香蕉多酚氧化酶褐变性质的研究

以邻苯二酚为废物通过采用分光光度计测定氧化产物的方法,对香蕉果肉中多酚氧化酶(PPO)的催化特性、最适温度、最适pH值、热稳定性等性质进行了研究。结果表明,香蕉PPO的最适温度为 25℃,最适 pH为 5.0,75℃水浴处理 5 min酶基本完全失活,100℃水浴处理20s可钝化PPO的活性,且香蕉PPO存在同功酶。实验中同时考察了柠檬酸、抗坏血酸、NaHSO_3和半胱氨酸对PPO的褐变抑制效果。     

CRISPR/Cas9介导的果糖低消耗酿酒酵母工程菌的构建

利用酿酒酵母为宿主,以果糖为原料合成D-阿洛酮糖具有食品方面的先天优势。为了减少酿酒酵母宿主本身对果糖的消耗,对酿酒酵母的己糖激酶同工酶2(Hexokinaseisoenzyme2,hxk2)基因进行编辑。本研究采用CRISPR/Cas9技术,构建了Cas9和gRNA共表达质粒p YES2-CG-Δhxk2,以酿酒酵母BY4741为出发菌株,URA3为筛选标记,采用高效电击转化法和胞内同源重组技术,获得hxk2基因缺陷株BY4741-Δhxk2。在此基础上,进行果糖发酵实验以评估突变菌株的果糖消耗速率。实验结果显示,发酵培养14 h时,缺陷株BY4741-Δhxk2果糖消耗速率为3.35 mg/h;与野生型菌株相比其下降了6.42%。此外,发酵培养22 h,BY4741-Δhxk2的OD600nm值为8.65,相比于野生型提高了6.40%。研究表明,己糖激酶hxk2基因的缺陷编辑可以一定程度降低酿酒酵母对果糖的利用,同时缺陷株较野生型表现出一定的生长优势,这为后续以酿酒酵母为宿主生产D-阿洛酮糖奠定了初步基础。     

Disentangling the Molecular Mechanisms of the Antidepressant Activity of Omega-3 Polyunsaturated Fatty Acid: A Comprehensive Review of the Literature

Major depressive disorders (MDDs) are often associated with a deficiency in long-chain omega-3 polyunsaturated fatty acids (ω-3 PUFAs), as well as signs of low-grade inflammation. Epidemiological and dietary studies suggest that a high intake of fish, the major source of ω-3 PUFAs, is associated with lower rates of MDDs. Meta-analyses of randomized placebo-controlled ω-3 PUFAs intervention-trials suggest that primarily eicosapentaenoic acid (EPA), but not docosahexaenoic acid (DHA), is responsible for the proposed antidepressant effect. In this review, we dissect the current biological knowledge on EPA and DHA and their bioactive lipid metabolites to search for a pharmacological explanation of this, to date, unexplained clinical observation. Through enzymatic conversion by cyclooxygenase (COX), lipoxygenase (ALOX), and cytochrome P-450 monooxygenase (CYP), EPA and DHA are metabolized to major anti-inflammatory and pro-resolving lipid mediators. In addition, both ω-3 PUFAs are precursors for endocannabinoids, with known effects on immunomodulation, neuroinflammation, food intake and mood. Finally, both ω-3 PUFAs are crucial for the structure and organization of membranes and lipid rafts. While most biological effects are shared by these two ω-3 PUFAs, some distinct features could be identified: (1) The preferential CYP monooxygenase pathway for EPA and EPA derived eicosanoids; (2) The high CB2 receptor affinities of EPA-derived EPEA and its epoxy-metabolite 17,18-EEQ-EA, while the DHA-derived endocannabinoids lack such receptor affinities; (3) The competition of EPA but not DHA with arachidonic acid (AA) for particular glycerophospholipids. EPA and AA are preferentially incorporated into phosphatidylinositols, while DHA is mainly incorporated into phosphatidyl-ethanolamine, -serine and -choline. We propose that these distinct features may explain the superior antidepressant activity of EPA rich ω-3 PUFAs and that these are potential novel targets for future antidepressant drugs.     

淀粉酶在真假蜂蜜中的区别

针对蜂蜜掺假和造假的问题,文中对真、假蜂蜜中的蛋白质含量、淀粉酶活性及淀粉酶同工酶谱带差异进行测定分析。结果表明,天然蜂蜜在低温条件下可以在近1个月的时间内保持其蛋白质含量和酶值基本不变,但是在高温的条件下,随着贮存时间的延长,其蛋白质含量和酶值就会明显下降。而假蜂蜜其蛋白质含量和酶值均没有明显的变化。同工酶凝胶电泳结果也表明,真、假蜂蜜中淀粉酶同工酶谱带明显不同。因此,通过跟踪测定蜂蜜中蛋白质含量、淀粉酶值变化、淀粉同工酶谱带可以检测蜂蜜的真假及其质量变化。     

血红素氧合酶-1在大鼠急性烧伤后心肌中的变化

目的研究重度烧伤组和热预处理组大鼠心肌损害及心肌血红素氧合酶-1（HO-1）变化规律。方法将66只Wistar大鼠按随机数字表法分为3组：对照组、烧伤组和预处理组,每组22只。烧伤组造成30%体表面积Ⅲ度重度烧伤（ⅢTBSA）,预处理组大鼠先经肛温42℃热预处理30 min,室温24 h后再予烧伤,烧伤后1、3、6、12、24 h处死大鼠,检测心肌酶、心电图、心肌普通病理以及心肌组织内HO-1 mRNA和蛋白水平的变化等情况。结果对照组大鼠心电图正常,烧伤组烧伤后6、12 hⅡ导联心电图ST段抬高最明显;预处理组烧伤后12hⅡ导联心电图ST段抬高最明显。病理结果显示：烧伤组烧伤后6、12 h心肌细胞结构明显破坏;预处理组烧伤后12 h心肌细胞结构破坏。正常大鼠心肌组织HO-1 mRNA和蛋白水平均较低,与对照组比较,烧伤后HO-1水平明显升高,mR-NA在6、12 h达到高峰,6、12 h的mRNA水平分别是对照组（3.21±0.67）、（2.24±0.52）倍,差异有统计学意义（P〈0.05）,HO-1蛋白则在12 h左右达高峰,为对照组的（9.6±1.8）倍（P〈0.01）。预处理组HO-1 mRNA 6、12 h水平分别是对照组（5.68±0.76）、（3.54±0.55）倍,与对照组比较差异有统计学意义（P〈0.05）;HO-1蛋白水平12 h为对照组（13.3±2.5）倍,与对照组比较差异有统计学意义（P〈0.01）。结论重度烧伤可造成明显心肌损伤,热预处理可减轻心肌损伤,热预处理减轻重度烧伤后心肌损伤可能与HO-1有关。     

激光辐照DNA导入番茄应用研究

激光与DNA作用将产生非线性共振、混沌、随机共振和随机混沌等非线性现象，使DNA变异、断裂．因此激光辐照DNA导入番茄，有益于供体的一些显性基因性状在受体后代得到表达，品质得到改善．对过氧化物酶同工酶的分析表明，受体后代与受体对照的同工酶图谱差异较大而与供体对照的同工酶图谱差异较小，这与它们在叶形与生长型表达上的差异是吻合的．这些表明了激光辐照DNA已经导入受体，并得到整合表达。     

激光辐照DNA导入番茄细胞色素氧化酶的研究

激光与DNA非线性作用会使DNA变异、断裂。因此激光辐照DNA导入番茄 ,有利于供体的一些显性基因性状在受体后代得到表达 ,品质得到改善。对细胞色素氧化酶同工酶的研究表明 ,受体后代与受体对照的同工酶图谱差异较大而与供体对照的同工酶图谱差异较小 ,这与它们在叶形与生长型表达上的差异是吻合的。这些表明了激光辐照DNA已经导入受体 ,并得到整合表达     

Origin of variable extraction of myosin from myofibrils treated with salt and pyrophosphate

When isolated myofibrils are treated with solutions containing NaCl and pyrophosphate to imitate conditions in meat being cured, considerable dijfirences are observed between myofibrils in the concentration of NaCl required for extraction of the myosin-containing A-band. The diferences in extent of extraction at an intermediate concentration of NaCl are between bundles of myofibrils rather than within them, indicating that the variation derives from differences between muscle fibres. The extraction behaviour is determined by the myosin isoenzyme content of the muscle fibre. Thus, the proportion of myofibrils extracted at an intermediate concentration of NaCl in preparations from various bovine and rabbit muscles reflects the documented proportion of fast-contracting fibres in each muscle. Rabbit M plantaris myofibrils from fast white fibres are extracted in a low concentration of NaCl, whereas those myofibrils containing slow myosin are extracted only in a high Concentration of NaCl. Myofibrils probably from fast red fibres require an intermediate concentration of NaCl for extraction.