辐射技术制备固定化蛋白酶

本文探讨了在低温条件下,~(60)Co-γ射线诱导亲水性单体丙烯酸羟乙酯、疏水性的聚乙二醇二甲基丙烯酸酯系列单体聚合固定化蛋白酶的方法,研究了单体的分子结构,单体性质对固定化蛋白酶活性和热稳定性的影响。实验结果表明,采用单官能团单体(HEA)制备的固定化蛋白酶相对活性高于双官能团单体,固定化酶相对活性随疏水性单体聚乙二醇二甲基丙烯酸酯中乙二醇数的增加而增加。对于亲水性单体HEA固定化蛋白酶的相对活性则随单体的冷却速率的增加而增加。固定化蛋白酶的热稳定性随单体的亲水性而变化。     

辐射聚合离子性水凝胶固定化酵母细胞

在低温(-78℃)下,通过辐照使2-丙烯酰胺2-甲基丙磺酸(TBAS)和聚乙二醇二甲基丙烯酸醇系列单体聚合,获得了具有离子性的水凝胶载体。用这些载体固定化酵母细胞的乙醇生产力均比游离细胞高,其中用poly TBAS-14G固定化细胞的乙醇生产力是游离细胞的4.5倍,每小时糖的转化率达50％。固定化酵母的活性随聚乙二醇二甲基丙烯酸分子中乙二醇数目的增加而增加。固定化酵母具有较高活性的原因是这些高分子载体具有一定的多孔性、膨胀性,载体带有电荷并具有一定的机械强度,固定化细胞能较好地繁殖,使载体内具有较高的细胞密度。     

低剂量超辐射敏感与诱导辐射抗性的研究进展

低剂量超辐射敏感(HRS)和诱导辐射抗性(IRR)是辐射生物学的两个重要现象,研究这两个现象发生的机理对于辐射保护、控制肿瘤发生、研制新的功能材料具有重要的意义。辐射产生的DNA双链断裂(DNA double-strand breaks,DSBs)是辐射诱导细胞失活的主要损伤形式。对DSBs不能进行修复或者不能进行正确的重新连接是引起细胞死亡的主要原因。与DNA合成前期(first gap phase,G1期)和DNA合成期(synthetic phase,S期)相比,HRS在DNA合成后期(second gap phase,G2期)的表现非常明显。HRS和IRR之间相互转换调控的机制可能是G2期细胞中的一部分存在一个激活过程的发生。DNA损伤修复机制在HRS/IRR过程中发挥了重要作用。在低于20cGy的剂量条件下,细胞产生效率较低的损伤效应,细胞死亡迅速增加,低剂量超辐射敏感现象(HRS)出现;在高于20cGy的条件下,辐射造成DNA双链断裂,这些DSB本身或者由辐射引起的DNA变化激活了ATM(ataxia telangiectasia mutated),G2期专有的检测点被激活,细胞周期在G2期停顿下来,激活的G2期专有的检测点促进对DNA进行修复,提高了细胞的存活率,此时,诱导辐射抗性(IRR)出现。尽管这些结果使人们对HRS/IRR有了一个比较清晰地了解,目前仍然存在着一些关键问题有待解决。例如,为什么有些细胞系表现HRS/IRR现象,而有些细胞系不表现HRS/IRR现象;细胞中是否存在针对单一剂量的突变的HRS/IRR等。这些问题可能是将来重要的研究方向。     

重离子辐射诱导玉米雄性不育突变系的遗传研究

利用30Gy7Li离子辐射玉米杂交种农大108的种子,从M3代材料中获得雄性不育突变材料39I3-2,并通过套袋杂交获得了不育材料的杂交组合。调查不育突变植株性状及其杂交组合和F2代雄花育性,结果表明,不育材料39I3-2花粉败育彻底,不育性状表现稳定,呈现出由隐性单基因控制的核不育的遗传特点。雄性不育突变体的出现与重离子辐射诱导有关,为基因突变的结果。     

栽培大麦辐射敏感性与进化的关系

大麦幼苗组织的过氧化物酶同工酶有3个酶带区,8条酶带。辐照后,在偏负极端出现一个新的酶带区,增加1—3条酶带。辐射剂量效应可用线性回归方程Y=A+BX拟合。大麦品种的过氧化物酶同工酶变化与辐射敏感性有关,与进化类型直接相关。协方差分析表明,裸大麦对辐射的敏感性显著高于皮大麦,四棱和六棱大麦则显著高于二棱大麦。据此可以认为,在进化上属原始类型的品种,辐射敏感性较低。     

辐射处理对水稻酯酶同工酶E_(St3)位点的影响初探

经测定分析,水稻阳极标志酶带E_3~S和E_3~F分别受E_(st3)位点上两个共显性基因控制,未经辐照处理的水稻品种"马坝糯"均表现出稳定的12A(慢带类型)酶带,而经26krad及44krad ~(89)Co γ射线辐照处理的M_2代则表现三种酶谱类型,即12A(慢带类型)、13A(快带类型)和12A/13A(互补类型)。辐照后由E_(st3)~S突变为其等位基因E_(st3)~F的频率分别为3.5%和5.06%。     

THE ADSORPTION OF COPPER BY SOIL MATERIALS AT LOW EQUILIBRIUM SOLUTION CONCENTRATIONS

The adsorption of copper by individual soil components (organic matter fractions, oxides and clay minerals) was examined at equilibrium solution concentrations of copper within the range found in natural soils, the distribution of copper between solution and solid phases being measured by means of labelling with radioactive ⁶⁴Cu. At these low solution concentrations it was found that the copper adsorption isotherms were essentially linear. The oxides and organic materials adsorbed the greatest amounts of copper. The concentration of copper in natural soil solutions will be controlled by these materials to a far greater extent than by the clay minerals, the influence of which may be negligible in some soils. Solution concentrations of copper are relatively unaffected by both the background concentration of major cations and by changes in pH within the ionic strength and pH range found in normal agricultural soils. Copper adsorption studies with humic and fulvic acids showed that total solution copper concentrations could be greatly enhanced above the equilibrium levels for ionic copper by the presence of soluble organic complexes. The importance of taking into account the presence of such copper complexes in soil copper studies is emphasised.     

吸附法固定化绿色木霉(Trichoderma reesei)生长细胞

本文应用辐射技术,在纸表面复盖不同性质的高分子,以此作为固定化生长细胞的载体,吸附绿色木霉细胞,并测定了固定化绿色木霉细胞的纤维素酶活性。当纸复盖有3种亲水性均聚体poly-HEA、poly-HEMA,poly-HPMA和一种疏水性均聚体poly-A4G时,细胞被吸附在这4种载体上,并能产生纤维素酶,但是只有复盖poly-HPMA的载体固定化细胞的纤维素酶活性(FPA)高于游离细胞。当纸复盖不同组成的HEA-A-TMPT、HEMA-A-TMPT.HPMA-A-TMPT和A4G-A-TMPT的共聚体时,用这些载体固定化细胞的FPA均比复盖均聚体的增加。用复盖不同组成的poly(HPMA-A-TMPT)载体固定化细胞,其FPA均比游离细胞增加,最高的增加了60％。用复盖有50％:50％和75％:25％的poly(HEA-A-TMPT)共聚体载体固定化细胞,其FPA分别比游离细胞增加了70％和60％。FPA增加是由于吸附的细胞重量增加,而固定化细胞的重量与复盖于纸上的高分子的性质(例如含水量)有关,复盖的高分子含水量10％左右时,固定化细胞重量最高,在载体表面复盖适宜的高分子有利于细胞的吸附和生长。     

极低温辐照大麦种子及热冲击后处理诱变效应的研究

本试验研究了极低温(-196℃)条件下γ射线辐照大麦干种子和极低温辐照结合热冲击后处理的诱变效应。结果表明:1.与常温条件下辐照相比,极低温条件下辐照及结合热击冲后处理均能显著减轻大麦M_1代的生理损伤和染色体畸变率,其半致死照射量分别提高13kR和30kR;2.M_2代的突变率随照射量升高而增加(r=0.9922~(··)),而与不同温度条件没有关系;3.在极低温条件下用50kR辐照及用60—65kR辐照结合热冲击后处理,与常温条件下用35—40kR辐照相比,没有加重M_1代的辐射损伤,而M_2代的突变率则显著增加,其诱变效率分别平均提高30％和48％。     

低温对弱光影响甜椒光合作用的胁迫效应

以弱光耐受性不同的甜椒(Capsicumannuum L.)幼苗为材料,研究弱光低温逆境下及其恢复过程中叶片光合特性、PSⅡ光化学活性和吸收光能分配的变化。结果表明,弱光低温及弱光适温处理均导致甜椒净光合速率(Pn)、PSⅡ光化学效率(ФPSⅡ)和光化学猝灭系数(qP)明显下降,PSⅡ光化学反应中心能量(P)显著减少,天线耗散(D),尤其是反应中心能量耗散(Ex)显著增加。弱光低温或弱光适温处理下Pn的下降是非气孔限制的结果,低温降低了植株的弱光耐受性。光温逆境解除后,甜椒光合碳同化的恢复滞后于PSⅡ光化学效率的恢复,并且弱光下不同试材对低温的耐受性有所不同。     

COPPER SORPTION BY SOILS AT LOW CONCENTRATIONS AND RELATION TO UPTAKE BY PLANTS

Copper sorption was measured in 14 agricultural soils from England and Wales with a wide range of properties. Sorption from 0.01 M CaCl₂ was described by the Freundlich adsorption isotherm when Cu in solution was initially at 200 HM and greater, but at lower initial concentrations (i. e. 100 fiM and less) there was a steep rise in the gradients of the isotherms. At initial concentrations of 100 JIM and less, sorption was linearly correlated to the concentration of Cu remaining in solution; the gradients of these relationships varied considerably amongst the soils and were highly correlated to soil pH. There was no correlation between either the gradients or the extrapolated values of final solution concentration at which there was no sorption of added Cu by the soils (an ‘equilibrium’ concentration), and other determined soil properties. The effect of pH adjustment on sorption varied between the 5 soils examined although, in general, there was increasing sorption with increasing pH. Extrapolated values for ‘equilibrium’ concentrations for an individual soil were higher at pH 6.0 or greater, than at pH 5.5. A large proportion of the Cu in the final solutions was apparently complexed but this varied between soils and was dependent on both pH and total concentration. There was little effect of varying pH of the final solution on these proportions in most soils. Neither extractable Cu in the soils, nor the sorption characteristics were related to availability as measured by uptake by perennial ryegrass.     

低温条件下玉米对磷素吸收的研究

用放射性核素~(32)P示踪研究表明,在5—25℃范围内,玉米苗期对磷的吸收随温度升高而增加,呈极显著正相关,相关系数为0.9747。苗期叶面喷磷能促进根系对磷的吸收,提高玉米的抗寒能力。喷磷后0.5小时遇50mm/h降雨,磷素冲刷率为42％,一般不需要重新喷磷。     

土壤微生物对施入肥料氮的固持及其动态研究

采集长期定位试验（１４年）土壤（棕壤）进行盆栽试验,并应用同位素＾１５Ｎ示踪技术研究了土壤中微生物对肥料氮的固持及其动态,结果表明,施肥后５天土壤微生物对施入人肥氮的固持达达到最高,除单施氮肥处理的固持量占施入人肥氮量的５．４％外,其余各处理均天１３．３％－１５．４％间,施肥后土壤微生物量氮的增加主要来自化肥氮,后者占微生物体总氮量的６４．１％－８７．３％,在作物生长期间微生物固持的化肥氮逐渐释入