温度对赤霉素诱导α—淀粉酶的影响（简报）

赤霉素诱导禾谷类种子α—淀粉酶的合成和分泌。本文以小麦种子为材料,观察到赤霉素在25℃条件下能强烈地诱导α—淀粉酶。不同温度下诱导的α—淀粉酶的最适反应温度(45℃)和最适pH值(pH 5.0)均无明显差异,但它们的同工酶类型完全不同,且对热的稳定性也明显不同。     

羊红细胞超氧化物歧化酶的研究

自羊红细胞分离得到一种高等电点的铜.锌-超氧化物歧化酶(Cu.ZnSOD)。其沉降系数(S)为3.23,亚基分子量为16600,等电点为8.50,紫外最大吸收峰位于259nm,酶分子中含有铜和锌,氨基酸组成特点与其它动物来源的Cu.Zn-SOD相同。该酶的比活性为5500U/mg(黄嘌吟氧化酶—细胞色素还原法);对KCN的抑制作用敏感,最适pH值为6。     

海水养殖真鲷弧菌病病原菌外毒素的理化特性

对最小弧菌Vm Pm毒素的分子量、分子结构及氨基酸组分进行了测定 ,同时还研究了温度、酸碱度及胰酶等因子对该毒素生物学活性的影响。研究结果表明 ,该毒素为单一的多肽 ,不具备典型的细菌毒素A、B亚基结构 ,分子量为 30 4 5 6kD ;毒素蛋白含天冬氨酸、苏氨酸、丝氨酸及半胱氨酸等 15种氨基酸 ,其中天冬氨酸的含量最多 ,半胱氨酸的含量最少 ,酸性氨基酸含量为 2 6 6 % ,碱性氨基酸含量为 14 4 % ,疏水性氨基酸含量为 33 4 % ;毒素活性的最适pH为 6— 8,对胰酶有抗性 ;不耐热 ,10 0℃下作用 1min ,其毒性完全消失 ,而在 5 6℃下 ,毒素完全失去活性需要 4 0min。     

小黑麦抗真菌蛋白组分的分离纯化和性质研究

以木霉为指示菌,小黑麦中饲237种子中的蛋白提取物经过分离纯化后,得到了3种主要的抗真菌蛋白组分,经酶活检测鉴定,分别是分子量为30.5 kD的ClassⅡ型几丁质酶,两种分子量为51kD和23 kD的β-1,3-葡聚糖酶。其中几丁质酶的最适反应pH为6.0,最适反应温度为37℃,测定的N末端氨基酸序列与大麦几丁质酶的有很高的同源性。在一定条件下,这3种蛋白组分都有较强的抗木霉活性,并且有明显的协同作用,同时它们对离体易感小麦叶片上白粉菌有很好的生长抑制作用。     

铬酸钾溶液紫外吸收特征及在研究UV-B生物学效应中的应用

为了更好地利用铬酸钾溶液去除UV-B光源中的UV-A和UV-C,对不同浓度和pH值的铬酸钾溶液的紫外吸收特征及其稳定性进行了相关研究.并在相同剂量UV-B作用下,对地木耳(Nostoc commune UETX-584)光合生理活性和生化组分在UV-B光源直接照射和经过铬酸钾过滤后照射的变化进行了对比研究.结果表明,铬酸钾溶液在pH值为8、0.4 mmol/L时可以有效滤除UV-B光源中的UV-C和大于340 nm的UV-A.相对于经过铬酸钾溶液过滤的UV-B光源,未过滤的UV-B光源显著抑制了地木耳的生长、叶绿素合成、Fv/Fm、最大光合作用速率和集光效率,显著促进了MAAs(三苯基咪唑类氨基酸)等吸收紫外辐射色素的合成.相对于无紫外辐射的地木耳来说,经过铬酸钾溶液过滤的UV-B对地木耳的生长影响不明显,但是其促进了紫外吸收色素的合成,抑制了Fv/Fm、最大光合作用速率和集光效率.     

高粱和小麦叶片苹果酸酶某些特性比较

比较高粱和小麦叶片的苹果酸酶的某些特性。发现高粱苹果酸酶对NADP-是专一的,未观测到NAD-苹果酸酶的活力。高粱叶片的NADP-苹果酸酶的最适pH随底物浓度不同而异;在0.5 mM苹果酸浓度下酶的最适pH是7.0～7.5,在1 mM和10 mM浓度下最适pH各为7.5～8.0和8.0～8.5,其中以底物浓度10 mM的活性最高。小麦苹果酸酶也具有类似的效应;但与高粱相比较活性较低。两种不同来源的苹果酸酶在动力学特性上有明显的差异,小麦叶片NADP-苹果酸酶的Km(苹果酸)值1.3比高粱大3.4倍。pH、Mg~(++)、Mn~(++)和苹果酸对高粱叶片NADP-苹果酸酶活力具有不同程度的调节作用;在不同pH条件下Mg~(++)、Mn~(++)对高粱叶片NADP-苹果酸酶表现出不同程度的协同性。Mg~(++)、Mn~(++)的亲和力随pH的升高而增大。而对小麦叶片NADP-苹果酸酶活性几乎无多大影响。在我们所试验的浓度下乙酰辅酶A、甘氨酸、葡萄糖-6-磷酸、果糖1-6二磷酸、琥珀酸以及延胡索酸对高粱NADP-苹果酸酶活性无影响。     

鄂尔多斯高原钝顶节旋藻SOD特性研究

采用邻苯三酚自氧化法确定了鄂尔多斯高原钝顶节旋藻SOD特性。该SOD在紫外光区320 nm处有最大吸收值;在Tris-HCl缓冲溶液中最适pH值为8.2,最适温度为25℃;pH值稳定性范围为6~10;高于40℃的条件下保温20 min酶活性开始下降,高于35℃条件下保温60 min酶活性开始下降;室温下存放2 d后活性开始下降,7 d时活性基本丧失;室温下避光保存9 d时SOD活性完全丧失。     

蓝藻水华堆积处理池中微囊藻毒素降解细菌的分离及降解特性

微囊藻毒素(microcystins, MCs)近年来由于蓝藻水华在世界范围内频发而受到广泛关注。从太湖北部蓝藻水华堆积处理池中分离出一株微囊藻毒素降解细菌SW1, 经16S rDNA序列分析鉴定为鞘氨醇单胞菌(Sphingopyxis sp.)。SW1的生长最适pH为中性(pH 6-8), 但也能生长于pH 10条件下。SW1对MCs的两种异构体MC-LR和MC-RR具有高降解活性, 并表现出一级反应动力学特征, 其降解速率常数分别为0.35/h和0.28/h。温度和pH对SW1降解活性有很强影响: 在温度为22-37℃, pH中性或弱碱性条件下(MC-LR, pH 6-9; MC-RR, pH 7-8), SW1具有高降解活性; 而在低温和强碱性条件下其降解活性受到强烈抑制。聚合酶链式反应(PCR)表明SW1及蓝藻水华堆积处理池均含有mlrA的同源基因, 表明处理池中存在MCs的生物 降解。       

石楠拟盘多毛孢毒素产生条件初探

石楠拟盘多毛孢是引起草莓根腐病的优势病原菌之一, 本实验在明确该病菌毒素是主要致病物质的基础上, 利用叶圆片法对该菌的产毒条件进行了初步探讨, 结果表明, 除光照影响不明显外, pH值、温度、振荡及培养时间等对此菌产生毒素均有显著影响, 其最适产毒条件为：培养基初始pH值为自然pH值(约为6.2)、温度为25°C、黑暗、静置培养5 d~7 d。此外, 实验还发现该菌产生的粗毒素对玉米、黑麦和绿豆种子萌发、根或芽的延伸生长都有明显的抑制作用。     

剑麻蛋白酶的分离纯化及其部分特性的研究

采用乙醇分步沉淀和 DEAE-纤维素柱层析,可从剑麻 Agave sisalana 叶汁中分离到一个均一的蛋白酶组分,其结晶为平面六边形。该酶可为半胱氨酸和 EDTA 所激活,受 PCMB(p-chloromercuribenzoatc)、DTNB(5,5′-dithiobis(2-nitrobenzoic acid))及 Hg~(2 )、Ag~( )、Cu~(2 )的可逆抑制和碘乙酸(pH 7.5)的不可逆抑制。该酶以酪蛋白为底物时,酶反应的最适 pH 值约为7.5,最适温度为50℃,Km 值为0.0625%酪蛋白,该酶在45℃(含45℃)以下较为稳定。且在6.0—10.0的 pH 值范围内稳定。     

Significance of 12S Toxin of Clostridium botulinum Type E

The pathogenesis of type E botulism is discussed as an aspect of the physicochemical and biological properties of 12S toxins (prototoxin and trypsin-activated 12S toxin) and the Ealpha and Ebeta components of each 12S toxin. A molecular weight of 350,000 was determined for each 12S toxin and 150,000 for Ealpha and Ebeta. Owing to the structure comprising the subunits Ealpha and Ebeta, 12S toxins are much more stable than Ealpha at low pH values and high temperatures. Such was also the case with type A 19S toxin and its alpha component. The Ealpha component alone accounts for the total toxicity of type E toxin. The toxic substance detected in the blood of the animals administered 12S toxins orally or parenterally was identified as Ealpha from the molecular size and the chromatographic pattern. Prototoxin escaping from detoxification in the stomach owing to the subunit structure may undergo dissociation in the intestine to release the Ealpha component. After absorption, the activated Ealpha appeared in the circulating blood without any further signs of dissociation or enzymatic digestion.     

Isolation and some properties of a novel killer toxin-like protein produced by Streptomyces sp. F-287.

A killer toxin-like protein was found in the culture supernatant of a strain isolated from soil. The strain was classified and designated as Streptomyces sp. F-287. The molecular weight of the purified killer toxin-like protein was estimated to be 9,500 by SDS-PAGE. The purified protein was heat stable (100 degrees C, 5 min), pH stable (pH 6.0-9.0, 60 degrees C, for 30 min), and had a relatively wide action spectra. The SKLP showed a cytocidal effect on both budding yeast, Saccharomyces cerevisiae W303 (IC50 = 15.6 micrograms/ml) and on fission yeast, Schizosaccharomyces pombe SP870 (IC50 = 20.0 micrograms/ml). The SKLP also caused morphological changes on some sensitive yeasts and filamentous fungi. These characteristics are apparently different from known killer toxins. These results suggest that this is a novel killer toxin-like protein from Streptomyces sp. strain F-287.     

高产红曲黄色素菌株的选育

利用紫外、硫酸二乙酯、氯化锂和亚硝基胍复合诱变的方法,选育到一株高产黄色素的红曲霉突变株MYM2.经过稳定性实验证明,诱变得到的菌株稳定性较好,液态发酵试验黄色素色价达到100U/mL以上,黄色素色调达到3.5左右.此黄色素在300nm～600nm波长之间只有一个在410 nm附近的最大吸收峰,在pH 3～8之间稳定性较好.当pH小于3时,红曲黄色素不稳定,黄色素溶液变混浊,放置后有沉淀产生.     

Analysis of the physicochemical interactions between Clostridium difficile toxins and cholestyramine using liquid chromatography with post-column derivatization

A potential therapy for antibiotic-associated pseudomembranous colitis is to bind Clostridium difficile toxins A and B using cholestyramine, a hydrophobic anion exchange medium. Frontal analysis in isotonic phosphate buffer was studied using post-column derivatization with o-phthalaldehyde, which gave a highly sensitive (> or =30 ng) flow-through analysis. Following load (1.5-3.0 microg toxin/3.6 mg), toxin A was bound at a slightly higher capacity than B, due to slower kinetics. A salt gradient eluted roughly 20% of bound toxin A with 0.6 M NaCl and toxin B with 1.1 M NaCl, hence toxin A showed weaker electrostatic affinity. The remainder of toxin A (65%) and some of toxin B (10% out of 50%) were eluted using a subsequent gradient to 60% acetonitrile in normal saline, which measured predominantly hydrophobic binding. Low and high affinity populations of both toxins were observed. Glycocholic acid or amino acids were competitive binders, although these components had little effect on the toxin A population bound primarily through ionic interactions. Competitive protein constituents in hamster cecal contents were also profiled. These results help to explain the variable clinical response in using cholestyramine to treat colitis. Using quaternary amine-polyhydroxymethacrylate (PHM) ion exchange chromatography, a trend for increased binding at higher pH was observed, especially for toxin A. Binding to strong cation exchange resins (sulfonate-PHM) was not observed. A range of reversed phase media retained both toxins, although recovery was very poor relative to protein standards. Size exclusion chromatography with light scattering detection showed that toxin B exists in different aggregation states, while toxin A remains monomeric.     

湖南尖吻蝮蛇毒两个出血毒素的纯化和理化性质

经ＳｅｐｈａｄｅｘＧ－７５凝胶过滤,ＱＡＥ－ＳｅｐｈａｄｅｘＡ－５０和ＣＭ－ＳｅｐｈａｄｅｘＣ－２５离子交换层析的步骤,从湖南产尖吻蝮（Ｄｉｅｎａｇｋｉｓｔｒｏｄｏｎａｃｕｔｕｓ）蛇毒中纯化出两个出血毒素（ＤａＨＴ－１和ＤａＨＴ－２）．ＳＤＳ－ＰＡＧＥ测得分子量均为２３．５ｋＤ,ＩＥＦ－ＰＡＧＥ测得等电点分别为５．６和５．２,两者具有相似的氨基酸组成,其中酸性氨基酸（Ａｓｘ,Ｇｌｘ）分别占２３％和２４％,ＤａＨＴ－１和ＤａＨＴ－２的最小出血剂量（ＭＨＤ）分别为０．５μｇ和０．８μｇ。都具蛋白水解酶活性,无对ＴＡＭＥ,ＢＡＥＥ的水解活性和ＰＬＡ２酶活性．两者的蛋白水解酶活力与出血活性并非正相关．ＤａＨＴ－１和ＤａＨＴ－２的最适温度分别为３５℃和４０℃,最适ｐＨ为６－９,对热均不稳定,温度高于６０℃活性完全丧失。金属离子的分析显示每摩尔毒素蛋白约含０．５ｍｏｌ的Ｚｎ,１ｍｏｌ的Ｃａ,较多的Ｎａ、Ｋ、Ｍｇ,不含Ｃｏ。     

Membrane-mediated killing of Saccharomyces cerevisiae by glycoproteins from Torulopsis glabrata.

Cell-free supernatants from cultures of Torulopsis glabrata contained glycoprotein toxins that killed sensitive and killer strains of Saccharomyces cerevisiae with single-hit kinetics. Growing S. cerevisiae treated with the toxins showed a leakage of cellular potassium, partial dissipation of the adenosine triphosphate pool, and a coordinate shutdown of macromolecular synthesis. These pool efflux-stimulating toxins have been partially purified and at least three toxic glycoproteins have been separated. Pool efflux-stimulating toxin activity was stable from pH 3 through 7, though killing was maximal close to pH 4.     

The photoconversion of heat-treated Chenopodium chlorophyll protein and its pH dependence

Photosensitive Chenopodium chlorophyll protein was purifiedby warming the complex in a boiling water bath, followed bypassing it through a Sephadex column. The shape and positionof the absorption band in the absorption spectrum of purifiedchlorophyll protein (HCP668) were the same as those of non-treatedchlorophyll protein (CP668), except for a change in the proteinband in the UV region. The chlorophyll protein retained a quarterof its original photoconvertibility after heat treatment for25 min at 100°C. Results suggested that the chlorophyll-aminoacid residue binding is very stable against heat, and that chlorophyllis protected from decomposition through the rigid binding. The photoconvertibility of HCP668, as well as CP668, dependedstrongly upon pH, with a pronounced decrease below pH 4 andabove pH 6. Optimal convertibility was at pH 5. Above pH 12,convertibility vanished completely. However, pH-inhibited convertibilityof HCP668 was recovered to its original level by returning thepH to neutral. Illuminalion of CP668 in D₂O with red light caused a markedincrease in light scattering. This reveals the occurrence ofa conformational change of apoprotein, leading to aggregation. HCP668 was degraded by mechanical treatment to give a smallersized photosensitive chlorophyll protein without loss of photoconvertibility.This small chlorophyll protein did not precipitate in a saturated(NH₄)₂SO₄ solution. The spectral properties of this complexwere identical to those of HCP668 and CP668. (Received March 21, 1972; )     

Standardized extraction method for paralytic shellfish toxins in phytoplankton

The optimal conditions were established for extraction of paralytic shellfish toxins from a Danish clone of Alexandrium tamarense using extraction with acetic acid and HCl in the concentration range 0.01–1.0 N. Physical destruction of the cells was investigated microscopically to select the most efficient extraction procedure.The toxin content was quantitated by an automized isocratic reversed-phase high-performance liquid chromatography (HPLC) method. The best results as judged from the total amount of toxins and the toxin profile were obtained using 0.05–1.0 N acetic acid and 0.01–0.02 N HCl. Hydrochloric acid in the concentration range 0.03–1.0 N caused the amount of C1 and C2 toxins to decrease sharply and concomitant increase of gonyautoxins 2 and 3.The phytoplankton extracts with 0.1 to 0.5 N acetic acid or 0.01 N HCl were stable during 6 months at –20 °C, but the extracts with HCl 0.02 N underwent a change in toxin profile, although the total amount of toxins was constant.     

金桂与丹桂醇溶性色素的提取及其稳定性比较

用不同体积分数的乙醇从金桂和丹桂的花瓣中浸提所含的花色苷类色素,用光谱扫描法检测该色素的光吸收特性,比较不同乙醇体积分数、不同浸提时间对色素浸提效果的影响,并进行光敏感性试验和酸碱影响试验。结果显示,金桂和丹桂的花色素用体积分数90%的乙醇浸提具较高的浸出率;延长浸提时间可提高色素浸出率;紫外线直射可使色素的色度大幅度下降,日光灯和散射光也会导致色度在一定程度上的下降;色素在酸性溶液中具一定的稳定性,但在碱性溶液中表现出不稳定性。