蔗糖脂肪酸酯对高压静电场与过氧化氢酶作用的影响

研究了蔗糖脂肪酸酯对高压静电场与过氧化氢酶作用的影响 ,结果表明 :在强度为 3× 10 3 v cm的电场作用下 ,蔗糖脂肪酸酯在 3.2mmol L的高浓度以上 ,可以保护过氧化氢酶不受高压静电场的影响。这可能是蔗糖脂肪酸酯使得溶液介电常数增大 ,使得作用在过氧化氢酶分子上的电场强度减小所致 ;在 1.4～ 1.6mmol L的浓度区间中 ,高压静电场使得过氧化氢酶的活力先增加后下降 ;在 0 .4～ 0 .7mmol L时 ,高压静电场使得过氧化氢酶的活力单调下降 ;在0 .0 0 8～ 0 .2 8mmol L的浓度范围内 ,高压静电场使过氧化氢酶的活力先下降后上升 ,可能使酶达到了一种新稳定态。蔗糖脂肪酸酯使得高压静电场对过氧化氢酶的作用变快 ,2～ 4min酶活力开始发生变化 ,而对照需要 2 0min以上。     

多羟基小分子对高压静电场与过氧化氢酶作用影响研究

研究了甘露醇、丙三醇对高压静电场与过氧化氢酶作用的影响 ,结果表明 :在强度为 3× 10 3 v cm的电场作用下 ,甘露醇在低浓度区使得过氧化氢酶的活力下降 ,这可能是甘露醇降低了溶液极性 ,使酶在高压静电场作用下容易变形所致 ;在中浓度区 ,过氧化酶活力上升 ;在高浓度区 ,甘露醇使得高压静电场对过氧化氢酶失去作用 ,这可能是甘露醇使得溶液介电常数增加 ,酶分子实际感受的电场强度减小所致。丙三醇的作用具有一定类似性     

高压静电场对离子溶液中过氧化氢酶的作用研究

研究了 KBr、磷酸缓冲液、Na Cl对高压静电场对过氧化氢酶作用的影响。结果表明 :浓度在 0 .0 2 m mol/L～ 0 .0 5 m mol/L的低浓度的无机离子对高压静电场对过氧化氢酶的作用影响很小。浓度在 0 .1mmol/L～0 .4 0 m mol/L的无机离子对高压静电压对过氧化氢酶的活力影响较大 ,过氧化氢酶在 3× 10 3V /cm的电场作用下活力只会升高。而对照出现先下降后上升的现象。浓度高于 0 .80 m mol/L时 ,无机离子可以保护过氧化氢酶不受高压静电场的影响。无机离子的这种效应可能是无机离子在高压静电场的作用下 ,产生反抗电场降低了高压静电场的强度所致。     

十二烷基硫酸钠对高压静电场对酶作用的影响

研究了十二烷基硫酸钠(SDS)对高压静电场对酶作用的影响。结果表明:在强度为3×103V/cm的电场作用下,十二烷基硫酸钠使过氧化氢酶对高压静电场的作用变得更加敏感。低浓度的十二烷基硫酸钠中,过氧化氢酶在高压静电场的作用下活力升高;0.04mmol/L～0.12mmol/L的十二烷基硫酸钠中,酶活力在高压静电场作用下先升高后下降;高于0.40mmol/L,则酶活力单调下降。十二烷基硫酸钠对高压静电场中的过氧化氢酶具有一定的保护作用。     

尼龙固定化木瓜蛋白酶及其应用研究

 尼龙经CaCl_2和H_2O的甲醇溶液处理,稀HCl水解用戊二醛交联以制备固定化木瓜蛋白酶。在溶液酶浓度为1mg/mL pH7.5—8.0、4—15℃条件下固定3h,活力回收42.5％,相对活力46％,偶联效率52％,半衰期72天。溶液酶Km值和固定化酶K_m~(aPP)值(底物酪蛋白W/V,％)分别为0.28％和0.35％。溶液酶和固定化酶分别在pH6.5和pH8.0以下活力稳定;最适pH分别为7.0和8.0;在65℃处理30min活力分别为原有活力的89％和66％。当酪蛋白浓度为1.5％和2.5％以上活力分别受到抑制。固定化酶在6mol/L脲中连续浸洗5次共6h其活力稳定,仍有原活力的44.4％;用以处理啤酒浊度比对照下降了2-11倍;蛋白质含量下降了55％;冷藏(4℃)120天,无冷混浊发生;同时各项理化指标和风味不变。     

0．23T稳恒磁场对不同温度离体过氧化氢酶的磁效应研究

研究了 0 .2 3T稳恒磁场对不同温度下的离体牛肝过氧化氢酶 (CAT)构象及活力的影响 ,并从分子水平讨论了磁场对不同温度的过氧化氢酶产生不同生物学效应的可能机制。将不同温度的天然酶液置于磁感应强度为0 .2 3T的磁场中分别处理一定的时间 ,处理过程中保持环境温度与酶液温度一致 ,撤离磁场后立即在相同实验条件下对其进行光谱分析及量热分析 ,并用Beers&Sizers法 (改良型 )测定酶活力。结果表明 ,磁场使 2 5℃过氧化氢酶的构象发生明显变化 ,表现为荧光偏振度增加、出现明显的差示扫描量热曲线、产生λ2 10nm～ 310nm的紫外差光谱以及λ330nm荧光发射峰的荧光强度改变 (荧光发射峰的峰位未移动 ) ,构象变化的同时酶活力增加 ;15℃过氧化氢酶的构象及活力变化规律与 2 5℃过氧化氢酶类似 ,但强度均弱于 2 5℃酶 ;而 4℃过氧化氢酶的构象及活力没有发生变化 ,表现出未受磁场处理的影响。相同实验条件下 ,磁场对不同温度的酶分子影响不同 ,随温度的增加 ,影响效应趋于显著。由于不同温度的酶分子之间的差异在于构象状态的不同 ,这表明酶分子自身的构象状态对磁场处理效果有极其重要的影响。不同温度的过氧化氢酶磁效应差异显著可能是由磁致酶构象变化的特殊机制所引起。磁场对酶分子构象的影响可能是通     

黑曲霉纤维素酶的纯化及酶学性质研究

黑曲霉(Aspergillusniger)固态发酵后粗酶液经硫酸铵盐析,2次SephadexG-200柱层析后可提纯8倍左右.CMC酶最适作用温度为60℃,最适作用pH为3.5,30℃～70℃区间酶活力较稳定,在pH3.0～5.0范围内,50℃保温30min能保持80%的酶活力.CMC酶的Km、Vmax值分别为7.69%CMCg/ml、0.33mg/ml·     

壳聚糖固定化木瓜蛋白酶的研究

以壳聚糖为载体,成二醛为交联剂将木瓜蛋白酶固定化。5％戊二醛在4-6℃下处理载体5h,加酶液(3.5mg/mL蛋白,pH7.2)固定12h,活力回收达32％,作用于酪蛋白的半衰期为36天,其表观K_m(酪蛋白)值为0.075％(W/V),溶液酶的K_m值为0.086％;最适pH7.0～7.5,溶液酶为7.0～8.5。固定化酶在pH8.5以下,溶液酶在9.0以下活力稳定。固定化酶在45℃以下,溶液酶在75℃以下稳定。用6mol/L脲洗脱固定化酶4次(5.5h)活力仍有54.5％。用固定化酶处理啤酒浊度比对照下降了1.5-3.7倍,蛋白质含量下降了44％,冷藏(4℃)120天无冷混浊现象发生并保持了啤酒原有风味和理化性状。     

高压静电场对黄瓜种子萌发期生理指标的影响

采用20 kV/cm高压静电场强度,分别以20、30、40 s处理黄瓜种子,结果表明:处理20 s的黄瓜种子在萌发期间各项生理指标均显著高于对照组。随处理时间延长,高压静电场对黄瓜种子萌发的促进作用减弱甚至产生抑制作用。     

高压静电场处理沙棘插条生根状况的初步研究

用高压静电场处理沙棘插条研究生根状况,方法简便易于处理,该装置适于进行大规模的处理,从目前研究表明：高压静电场对沙棘插条有正刺激效应,并以电场强度为３．９ｋｖ／ｃｍ,时间为４０分钟处理最佳。     

Changes in the Activity of Catalase (EC 1.11.1.6) in Relation to the Dormancy of Grapevine (Vitis vinifera L.) Buds

Catalase activity in grapevine (Vitis vinifera L.) buds cv. `Perlette.' increased to a maximum in October and thereafter decreased within 3 months to less than half its maximal rate. The decrease in catalase activity coincided with the decline in temperature during winter. The rate of sprouting of buds forced at 23°C was negatively related to the activity of catalase. Artificial chilling of grapevine canes at 5°C resulted in a 25% decrease of catalase activity in the buds after 3 days and 31% after 17 days. The activity of catalase increased to the control level only 96 hours after removing canes from 5°C to room temperature. Efficient buddormancy breaking agents, such as thiourea and cyanamide decreased catalase activity to 64 and 50% of the controls respectively, while the activity of peroxidase remained the same under those conditions. A less efficient dormancy breaking agent dinitro-ortho-cresol, did not decrease catalase activity.     

Regulation of Catalase Activity in Leaves of Nicotiana sylvestris by High CO(2)

The effect of high CO₂ (1% CO₂/21% O₂) on the activity of specific forms of catalase (CAT-1, -2, and -3) (EA Havir, NA McHale [1987] Plant Physiol 84: 450-455) in seedling leaves of tobacco (Nicotiana sylvestris, Nicotlana tabacum) was examined. In high CO₂, total catalase activity decreased by 50% in the first 2 days, followed by a more gradual decline in the next 4 days. The loss of total activity resulted primarily from a decrease in CAT-1 catalase. In contrast, the activity of CAT-3 catalase, a form with enhanced peroxidatic activity, increased 3-fold in high CO₂ relative to air controls after 4 days. Short-term exposure to high CO₂ indicated that the 50% loss of total activity occurs in the first 12 hours. Catalase levels increased to normal within 12 hours after seedlings were returned to air. When seedlings were transferred to air after prolonged exposure to high CO₂ (13 days), the levels of CAT-1 catalase were partially restored while CAT-3 remained at its elevated level. Levels of superoxide dismutase activity and those of several peroxisomal enzymes were not affected by high CO₂. Total catalase levels did not decline when seedlings were exposed to atmospheres of 0.04% CO₂/5% O₂ or 0.04% CO₂/1% O₂, indicating that regulation of catalase in high CO₂ is not related directly to suppression of photorespiration. Antibodies prepared against CAT-1 catalase from N. tabacum reacted strongly against CAT-1 catalase from both N. sylvestris and N. tabacum but not against CAT-3 catalase from either species. This observation, along with the rapid changes in CAT-1 and the much slower changes in CAT-3 suggest that one form is not directly derived from the other.     

高压静电场分离水稻、油菜及芝麻种子对萌发期生物效应的影响

落入高压静电场内的水稻、芝麻及油菜种子,在场的作用下,即产生沿电场方向的位移,在同一跌落高度下,重量基本相同的种子,其分离距离产生很大的差异,且分离距离与种子的发芽率及发芽势的改善程度存在着较为明显的相关关系,研究中证实,种子活力强度得到提高,其α淀粉酶活性、蛋白酶活性、脂肪酶活性及电导率得到明显的改善。     

Effect of elevated temperature on catalase and superoxide dismutase during maize development

Seeds of the inbred maize lines, W64A, R6-67, and D10, were germinated and grown at 25 degrees, 35 degrees, or 40 degrees C for up to 10 days. The catalase activity in scutella of W64A seedlings grown at 40 degrees C was slightly lower than that in seedlings grown at 25 degrees C. The total superoxide dismutase activity in scutella was lower in seedlings grown at 40 degrees C than in those grown at 25 degrees C during the first 3 days of germination, but thereafter was not significantly different at these temperatures. The high-catalase mutant lines, R6-67 and D10, grown at 40 degrees C exhibited a developmental pattern of catalase activity that was severalfold lower than that seen in seedlings grown at 25 degrees C. The decrease in catalase activity in R6-67 seedlings grown at 40 degrees C was correlated with lower amounts of CAT-2 protein, which is normally present at significantly high levels in this line. The application of a catalase synthesis inhibitor revealed that the low levels of CAT-2 in R6-67 grown at 40 degrees C were due to slightly higher degradation rates and a significant drop in the rate of catalase protein synthesis.     

Electrostatic Tuning of Cellular Excitability

Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability.     

A possible role of the Na(+)/K(+)-ATPase for O(2) production from H(2)O(2)

We are attempting to supply a new insight on interaction between Na(+)/K(+)-ATPase and H(2)O(2). We demonstrate that in vitro the Na(+)/K(+)-ATPase, a non heme-protein, is able to disproportionate H(2)O(2) catalatically into dioxygen and water, as well as C(40) catalase. By polarography, we quantify O(2) production and by Raman spectroscopy H(2)O(2) consumption. A comparative analysis of kinetics parameters relative to O(2) production shows that for Na(+)/K(+)-ATPase the affinity of the catalytic site able to transform H(2)O(2) into O(2) is twice weaker than that for C(40) catalase. It also shows that the molar activity for O(2) production is 300-fold weaker for ATPase than for catalase. Inhibitors, pH and GSH studies highlight the differences between the heme- and nonheme-proteins. Indeed, for C(40), NaN(3) is strongly inhibiting, but much less for ATPase. The pH range for the catalatic activity of ATPase is wide (6.5 to 8.5), while it is not for C(40) catalase (optimum at pH 8). The Na(+)/K(+)-ATPase catalatic activity is reduced in presence of glutathione, while it is not the case with C(40) catalase.