Effects of a new inhibitor K-23 on electron transport in photosystem II of higher plants

The effects of inhibitor K-23 on variable fluorescence, oxygen evolution and DCIP photoreduction were investigated. K-23 promotes the oxygen evolution and DCIP photoreduction at low concentration and inhibits them at relatively high concentrations, while an efficient inhibition at low concentration is found in variable fluorescence. These data further confirm that the inhibitor K-23 action is based on its redox interaction rather than quenching effect. Addition of DPC could not restore the DCIP photoreduction activity. It is suggested that the inhibitory site is at the acceptor side. Using ferricyanide as electron acceptor, the effect of K-23 and DCMU on the oxygen evolution of trypsin-treated thylakoids was investigated. It is found that oxygen evolution of trypsin-treated thylakoids was insensitive to DCMU, whereas became more sensitive to K-23 and also the promotion of K-23 at low concentration disappeared. This strongly indicates that trypsin treatment modified the binding site of K-23 and increased its accessibility to K-23 target site. From the comparison of K-23 with DCMU, we conclude that the binding site of K-23 is different from that of DCMU even though they both bind at the acceptor side.     

大豆胰蛋白酶抑制剂的研究进展

从结构、毒理学分析和灭活方法3个方面对国内外近年来对大豆胰蛋白酶抑制剂的研究进展进行了综述。     

海南省土壤拮抗放线菌分离方法初探

针对海南土样拮抗放线菌的分离,实验初步解决了土样中的细菌和真菌在放线菌分离培养中的污染问题。研究测定了细菌和真菌抑制剂K2Cr2O7的最佳使用浓度、土样稀释浓度、土样加热和风干处理以及土样的贮存时间等对放线菌分离培养的影响。结果表明：K2Cr2O7在一定的浓度范围内使用可以明显抑制细菌的生长,对放线菌的生长无明显的影响,浓度在50μg／ml时效果最佳。当K2Cr2O7 的使用浓度在70μg／ml时放线菌生长受到抑制,使用浓度在30μg／ml时对细菌的抑制效果不明显;土样溶液涂抹平板培养时,土样溶液浓度在10-3~10-4时平板内长出的菌落在30~40个间,菌落的重叠率在20%左右,分离效率较高,是理想的浓度;在土样放置一个星期的自然风干后,同时使用细菌抑制剂K2Cr2O7可得到较理想的培养效果;对土样进行加热处理后,可明显降低细菌的数量,但同时也会降低放线菌数量,分离效率过低。     

杨桃果实过氧化物酶特性及其抑制条件研究

以愈创木酚为底物,采用分光光度法对杨桃果实过氧化物酶（POD）的酶学特性进行研究。结果表明,杨桃POD反应时间不宜超过3.5 min,最适pH为 5.6,最适温度为30 ℃,100 ℃处理 30 s 后 POD 活性完全丧失。POD催化的酶促褐变反应动力学符合米氏方程,动力学参数Km=1.68×10-2 mol/L,Vmax=15.267 U/min,相应的动力学方程为v=15.267[S]/(0.0168+[S])（U/min）。抑制剂对 POD活性的抑制效果从大到小依次为抗坏血酸＞L-半胱氨酸＞亚硫酸氢钠＞柠檬酸。本研究可为杨桃保鲜贮藏和深加工过程中的酶促褐变控制提供理论参考。     

抑制剂处理对杨桃汁酶促褐变的影响

[目的]为加工优质杨桃汁提供试验依据。[方法]以新鲜杨桃为原料,将其与抑制剂（柠檬酸、抗坏血酸、盐酸-L-半胱氨酸、氯化钙等）一同打浆后制备杨桃果汁,探讨不同浓度抑制剂处理对杨桃汁酶促褐变的抑制效果。[结果]4种抑制剂中,抗坏血酸对杨桃汁酶促褐变的抑制效果最好,添加量≥0.04%的抗坏血酸可有效抑制杨桃汁酶促褐变;单一的氯化钙处理对杨桃汁酶促褐变的抑制效果较差,但氯化钙与抗坏血酸2种抑制剂复合处理对杨桃汁褐变度具有明显的加成效应影响,其中0.02%Vc＋0.1%CaCl2的复合抑制剂处理对杨桃汁酶促褐变具有明显的抑制效果。[结论]该研究筛选出了优质杨桃汁加工过程中的最佳抑制剂组合。     

外施亚精胺及其抑制剂对黄瓜去顶苗雌花分化中生化物质变化的影响

[目的]进一步探讨外源亚精胺（Spd）调控雌花分化的生理基础。[方法]研究外源Spa及其抑制剂DCHA（二环己胺）对黄瓜去顶苗雌花分化中生化物质变化、雌花分化率的影响。[结果]Spd处理的黄瓜去顶苗在雌花分化中嫩枝的可溶性蛋白质含量明显高于CK组的,而抑制DCHA处理的却低于CK组的;Spd处理的黄瓜去顶苗嫩枝的可溶性糖含量于接种后30d时出现峰值,而DCHA处理的含量低于Spd处理及CK组的;接种后24～27d,Spa处理、CK组黄瓜去顶苗嫩枝的淀粉含量30d前后快速上升,33d后再下降;在雌花初现（培养30d）之前,Spa处理的黄瓜去顶苗嫩枝的叶绿素（a十b）含量呈快速上升趋势。[结论]外源Spd促进了黄瓜去顶苗的可溶性蛋白质、可溶性糖、淀粉、叶绿素（a＋b）含量和雌花分化率的提高,DCHA的作用与之相反。外施Spa引起的黄瓜去顶苗的生理指标变化有利于雌花分化。     

荞麦BTI全长基因的克隆及表达分析

【研究目的】扩增荞麦胰蛋白酶抑制剂(Buckwheat trypsin inhibitor,BTI)基因,并对其表达特性和氨基酸同源性进行分析。【方法】根据荞麦胰蛋白酶抑制剂氨基酸的保守序列设计简并引物,采用RT-PCR和RACE技术,以荞麦cDNA为模板,扩增BTI基因并进行序列及其表达谱分析。【结果】克隆得到了BTI基因。它的cDNA全长为459bp,含有一个216bp的完整阅读框,编码72个氨基酸。同源性分析表明,其蛋白质序列与已报道的荞麦种子提取的BWI-1的氨基酸序列的同源性达96%,与笕属植物ATI、亚麻属植物Luti、马铃薯蛋白酶抑制剂PPI-I的氨基酸序列的同源性分别为65%、59%、48%。RT-PCR分析表明,BTI基因可在不同的组织中进行表达,但经伤害处理后的叶片中其表达量略高于生长各阶段。这可能与逆境情况(如外界损伤)下的应答等生理过程有关。【结论】荞麦BTI基因的获得,可为荞麦胰蛋白酶抑制剂的基础及应用研究奠定基础。     

Effects of a phospholipase D inhibitor on postharvest enzymatic browning and oxidative stress of litchi fruit

Membrane lipid degradation catalyzed by phospholipase D (PLD) results in postharvest browning and senescence of litchi fruit. The effects of n-butanol, a specific PLD inhibitor, on enzymatic browning and oxidative stress during storage of litchi fruit at room temperature were evaluated. n-Butanol-treated fruit had a lower browning index and disease index than untreated fruit. n-Butanol treatment also decreased PLD activity. As a result, the decompartmentalization of litchi polyphenoloxidase and substrates was reduced. The conversion of substrates (−)-epicatechin and procyanidin A₂ into quinones was slowed down and enzymatic browning of litchi pericarp tissues was lower after 6 d storage. Additionally, n-butanol-treated fruit possessed significantly lower malondialdehyde contents than untreated fruit after 4 d storage. Analysis of antioxidative enzyme activities showed that n-butanol treatment inhibited oxidative stress mainly by maintaining high catalase activity in litchi pericarp tissues. Consequently, senescence of litchi fruit during storage was moderated.     

白菜型油菜显性核不育的遗传分析及选育方法研究

研究结果表明,白菜型油菜细胞核雄性不育３７ＡＢ是受２对显性抑制基因控制的新雄性不育类型,分为杂合基因型和纯合基因型两类,采用简单成对保持双隐性测交方法,经２￣３个世代连续选育,能分离筛选出纯合基因型不育系,实现显性细胞核雄性不育的三系配套。