黄嘌呤氧化酶法优化大鼠血清SOD 测定条件的探讨

目的:优化黄嘌呤氧化酶法测定大鼠血清SOD实验条件.方法采用黄嘌呤氧化酶法,探讨其加样量、方法重复性、显色稳定性、试剂稳定性及样品稳定性等最佳因素.结果黄嘌呤氧化酶法测定大鼠血清SOD最佳加样量为5μl,其测定变异系数CV＜1%,显色前后20 min吸光度比较(P＞0.05);新配试剂与配制3个月试剂做测定,吸光度比较...     

汤汁辅料对腐乳发酵过程中单胺氧化酶活性及生物胺积累的影响

传统发酵腐乳中的生物胺是威胁消费者健康的潜在风险因素,为开发符合大众健康要求的低盐腐乳并降低腐乳中的生物胺含量,探讨了汤汁辅料对腐乳发酵过程中单胺氧化酶活力及生物胺积累的影响。配制不同食盐浓度、酒精浓度、pH值的腐乳汤汁,分析腐乳发酵过程中单胺氧化酶活力、生物胺含量变化。实验结果显示:当汤汁中的食盐质量分数为3%~7%,酒精体积分数为15%~25%,且pH值为4.5~5.5时,发酵前30d腐乳中的单胺氧化酶活性下降,发酵中后期(40~80d)活性回升。生物胺总量及组胺、色胺积累量呈现先升高,45d后逐渐降低趋势;发酵20~45d时生物胺积累总量呈现峰值,基本维持在6.5mg/g以下,以后逐渐降低;发酵80d结束时,各实验组生物胺积累量均为2.0~4.8mg/g,组胺和色胺积累量为0.6~1.8mg/g,3%食盐组生物胺积累量较高。研究结果表明,腐乳发酵过程中单胺氧化酶活性与生物胺积累呈现显著负相关,食盐、酒精及pH值影响腐乳产品的生物胺总量及其种类组成,其中组胺、色胺为腐乳的主要生物胺组分,酪胺含量很低。因此开发低盐化腐乳在降盐的同时,需要配合高酒精、低pH值等综合措施,以提高其食品安全性及风味品质。     

基于抗体的小麦赤霉病抗性研究进展

 由镰刀菌引起的小麦赤霉病,不仅降低产量和品质,所形成的真菌毒素还会影响食品安全。植物缺乏高抗小麦赤霉病的资源,因此从动物中筛选、分离抗病抗体及其基因,可为培育植物抗病品种提供新种质,也拓展了开发研究新抗源的渠道。抗病抗体能特异靶向真菌蛋白、抑制抗原的功能;抗体与抗菌肽和顺式表达调控元件结合,使病菌能诱导抗体融合蛋白在镰刀菌侵染小麦的颖壳高效表达,从而有效抑制病菌侵入、扩展及毒素积累。本文综述抗病抗体的抗原类型、抗病抗体及其融合蛋白在体外和植物中的表达以功能、抗原基因结构与功能、抗体抗病机理的研究进展。     

酶的研究与生命科学(二):氧化酶和ATP酶的研究

生物氧化是机体能量生成的基础,是生命得以维持的基本保证。细胞色素氧化酶的发现开启了现代生物氧化研究的序幕:一方面鉴定了大量氧化酶,从而充实了氧的利用特征;另一方面脱氢酶及辅助因子的鉴定进一步理解了生物氧化的本质为氢与氧结合生成水,同时释放能量促使ATP生成的过程。ATP合酶和Na+,K+-ATP酶的发现推动了对ATP生成和利用机制的研究。许多酶的催化都需要ATP的辅助,如泛素连接酶等,相关研究拓展了对细胞内物质代谢的认识。笔者通过生物氧化(亦称生物能学)发展过程的介绍而展现氧化酶和ATP酶的重要性。     

吡喃糖氧化酶电极对葡萄糖和木糖的响应特征

采用戊二醛交联方法,将葡萄糖氧化酶(GOD)和吡喃糖氧化酶分别固定在醋酸纤维素载体膜上,制备电流型电化学酶电极。在SBA双电极分析仪器上安装葡萄糖氧化酶电极和吡喃氧化糖氧化酶电极,分别对不同浓度的葡萄糖、木糖及葡萄糖木糖混合样品进行测试,以葡萄糖氧化酶电极为对照,研究吡喃糖氧化酶电极对葡萄糖、木糖的响应特征。结果表明,吡喃糖酶电极对葡萄糖和木糖都具有良好的响应特征。葡萄糖测定的精密度（RSD）为1.10%（n=10）,在10~1 000 mg/L范围内有良好的线性相关性（R=0.999 0）;木糖测定的RSD为0.80%（n=10）,在10~1 600 mg/L范围内有较好的线性相关性（R=0.999 8）;在葡萄糖木糖混合液测定时,吡喃糖氧化酶电极呈现明显的双底物催化特征,在一定的浓度范围内,对葡萄糖和木糖的响应具有线性相关性。     

The presence of free D-amino acids in mouse tissues

Summary The presence of free D-amino acids in mouse kidney, liver, brain, heart, lung, thymus and serum has been shown with an enzymic microdetermination method. The D-amino acid levels were higher in the extracts of kidney and liver than in those from other organs.     

L-gulonolactone oxidase is present in the invertebrate,Limulus polyphemus

Summary L-Gulonolactone oxidase (EC 1.1.3.8) which catalyzes oxidation of L-gulonolactone to L-ascorbic acid was detected in tissues ofLimulus polyphemus.     

Biochemical effects and growth inhibition in MCF-7 cells caused by novel sulphonamido oxa-polyamine derivatives

The novel polyamine derivatives sulphonamido oxa-spermine (oxa-Spm) and sulphonamido oxa-spermidine (oxa-Spd) exhibited rapid cytotoxic action towards MCF-7 human breast cancer cells with IC₅₀ values of 4.35 and 6.47 μM, respectively, after 24-h drug exposure. Neither compound is a substrate of serum amine oxidase. Both oxa-Spm and oxa-Spd caused cell shrinkage, as determined by phase-contrast microscopy. After incubation with 10 μM of either compound for 8 h, the cells underwent chromatin condensation and nuclear fragmentation. However, no clear DNA ladder was obtained by electrophoresis. The sulphonamido oxa-polyamine derivatives and especially oxa-Spd enhanced the activity of polyamine oxidase (PAO), an enzyme capable of oxidising N¹-acetylated spermine and spermidine to spermidine and putrescine, respectively, generating cytotoxic H₂O₂ and 3-acetamidopropanal as by-products. The intracellular polyamine content was only marginally reduced in response to drug treatment. In conclusion, our data show that these novel sulphonamido oxa-polyamine derivatives possess high cytotoxic activity against MCF-7 cells and indicate that induction of PAO may mediate their cytotoxicity via apoptosis. Received 17 January 2002; received after revision 22 February 2002; accepted 22 February 2002     

Morphofunctional changes in the mitochondrial subpopulations of conceptus tissues during the placentation process

To establish the role of mitochondrial subpopulations in the mitochondrial maturation process, we studied morphological and functional changes in the mitochondria of different mammalian conceptus tissues during the organogenic and the placentation processes. Mitochondrial subpopulations of three different conceptus tissues, embryo and visceral yolk sac placenta on gestational days 11, 12 and 13 and placenta on days 12 and 13, were examined morphologically by transmission electron microscopy. Cytochrome oxidase activity and protein levels were also measured in each mitochondrial subpopulation. The results indicate two different mitochondrial subpopulation profiles: a homogeneous one, which corresponds to immature mitochondria, and a heterogeneous one, which represents the mature mitochondria. The three tissues studied show different morphologic and metabolic patterns of mitochondrial maturation during the placentation process, rendering them suitable as experimental models to establish the p ossible relationship between mitochondrial maturation and the mitochondrial subpopulations. Received 5 August 2002; received after revision 23 September 2002; accepted 8 October 2002 RID="*" ID="*"Corresponding author.     

肌酐测定工具酶产生菌-烟草节杆菌02181的筛选及其产酶条件

肌酐酶、肌酸酶和肌氨酸氧化酶是肌酐测定酶学方法的主要工具酶，我们从兰州市郊土壤中筛选到一株能同时高产这3种酶的菌株02181，经中国科学院微生物研究所鉴定为烟草节杆菌，正式定名为烟草节杆菌02181(Arthrobacter nicotianae 02181)．该菌适宜的培养温度为28℃；增加氧溶量有利于细菌细胞生长和产酶；肌酐的存在对产酶至关重要，推测为酶基因开放的诱导剂；蛋白胨是该菌生长和产酶的良好氮、碳源；在有肌酐和蛋白胨存在时，添加葡萄糖能促进细菌细胞生长，但产酶量降低；镁盐、钾盐和磷酸盐为细菌生长和产酶所必需．优化产酶条件后，肌酐酶、肌酸酶和肌氨酸氧化酶的最高产酶量分别达145．00U／g湿菌、75．77U／g湿菌和21．30U／g湿菌．该菌不仅具有用于发酵生产的潜力，也为我们进行肌酐测定3种主要工具酶的基因克隆奠定了基础。