N~+离子注入对不同辐射敏感性微生物超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性的影响

以Ｅ．ｃｏｌｉ和耐辐射生球菌（Ｄｅｉｎｏｃｏｃｃｕｓｒａｄｉｏｄｕｒａｎｓ）为试材,研究了Ｎ＾＋离子注入对其ＳＯＤ,ＣＡＴ和ＰＯＤ活性的影响及共对自由基的清除,结果表明：Ｄ．ｒａｄｉｏｄｕｒａｎｓ经Ｎ＾＋离子注入后ＳＯＤ和ＣＡＴ酶活高于Ｅ．ｃｏｌｉ的,而ＰＯＤ酶活不仅很低于Ｅ．ｃｏｌｉ的;随剂量的增大,两者ＳＯＤ和ＣＡＴ酶活均为增后减,只是其ＳＯＤ酶活的变化峰值对应剂量分别为６×１０＾１５Ｎ＾＋／     

离子注入对耐辐射微球菌存活及生物量的影响

以耐辐射异常微球菌（Ｄ．ｒａｄｉｏｄｕｒａｎｓ）为试材,研究了离子注入对其存活和生物干重的影响。结果表明,不同能量和不同种类的离子注入Ｄ．ｒａｄｉｏｄｕｒａｎｓ,其存活均表现为先降后升再降的变化,即存活曲线呈现为相似的“马鞍型”,只是在不同种类的离子注入中,注入能量为２０ｋｅＶ的原子质量较大的Ｎ＋离子比Ｈ＋对其存活和生物干重的影响较大;在不同能量的离子注入中,能量相对较高的３０ｋｅＶ的Ｎ＋离子注入比２０ｋｅＶ的影响大。离子注入生物体产生这种不同于其它电离辐射的存活规律,意味着其对生物体的作用机理显著不同于其它电离辐射。     

N~ 离子注入对不同辐射敏感性微生物超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)活性的影响

以Ｅ．ｃｏｌｉ和耐辐射微球菌（Ｄｅｉｎｏｃｏｃｃｕｓｒａｄｉｏｄｕｒａｎｓ）为试材,研究了Ｎ＋离子注入对其ＳＯＤ、ＣＡＴ和ＰＯＤ活性的影响及其对自由基的清除。结果表明：Ｄ．ｒａｄｉｏｄｕｒａｎｓ经Ｎ＋离子注入后ＳＯＤ和ＣＡＴ酶活高于Ｅ．ｃｏｌｉ的,而ＰＯＤ酶活不仅很低也低于Ｅ．ｃｏｌｉ的;随剂量的增大,两者ＳＯＤ和ＣＡＴ酶活均为先增后减,只是其ＳＯＤ酶活的变化峰值对应剂量分别为６×１０１５Ｎ＋／ｃｍ２和２×１０１５Ｎ＋／ｃｍ２,而ＣＡＴ的则均为４×１０１５Ｎ＋／ｃｍ２;它们的ＰＯＤ酶活变化则不同,各处理耐辐射微球菌ＰＯＤ酶活保持低而恒定的水平,而大肠杆菌的则是中低剂量较恒定,较高剂量逐渐增大;对１０１６Ｎ＋／ｃｍ２注入的细胞培养到后对数期,再测其自由基ＥＳＲ波谱信号强度,发现比同剂量注入、未进行培养的要弱的多。     

三种辐射源对耐辐射微球菌作用机理的比较研究

三种辐射源对耐辐射微球菌作用机理的比较研究宋道军余增亮（中国科学院等离子体物理研究所离子束生物工程研究中心合肥２３００３１八十年代中期创立于我国的低能重离子生物学,研究已证实注入离子对植物和微生物均有良好的诱变效应［１－４］。离子注入生物体集能量沉积...     

种子辐射诱导发光与辐射敏感性关系的研究

种子辐射诱导发光随时间的延长,发光强度及发光强度的衰减速度逐渐降低．发光强度的衰减规律接近二级动力学反应规律．每粒种子吸收单位剂量辐射所产生的诱导发光强度及浸种初期的发光强度与幼苗的相对苗高之间具有显著的相关关系,这说明辐射敏感性高的种子吸收单位剂量在单粒种子内产生的诱导发光强度也高．辐照种子发芽后的发光强度比未辐照种子低．     

中药中耐辐射微生物的分离与鉴定

从中成药(金锁丸)中分离获得一种耐辐射的细菌。经过形态观察、生理生化特征分析及16 S rDNA碱基序列测定和同源性分析,鉴定该菌株为弯曲芽孢杆菌(Bacillus flexus),该菌株的16 S rDNA序列已在Gen-Bank中注册,登录号为AB021185.1。     

CKS1 表达与食管癌细胞辐射敏感性的关系研究

目的:探讨CKS1表达对食管癌细胞辐射敏感性的影响,初步研究其分子机理.方法:用Western-blotting方法筛选CKS1低表达和高表达的食管癌细胞系;构建CKS1正义表达载体p-pcDNA 3.1/myc-His A-CKS1和RNA干扰载体CKS1 siRNA,分别转染CKS1低表达细胞和高表达细胞,用不同剂量γ-射线照射各组细胞,克隆形成实验检测细胞辐射敏感性的差异.结果:CKS1在四种食管癌细胞中的表达水平依次为EC9706＞ KYSE510＞KYSE450＞ KYSE150.用p-pcDNA 3.1/myc--His A-CKS1表达载体转染KYSE150细胞后CKS12表达升高,不同剂量γ-射线照射后细胞的克隆形成能力显著高于母系对照组(P＜0.01).RNA干扰载体转染KYSE510细胞后CKS1表达水平降低,不同剂量γ-射线照射后细胞的克隆形成能力显著低于母系对照组(P＜0.01).敲降CKS1表达后DNA损伤修复相关蛋白RAD51表达下降,KU70表达没有变化.CKS1过表达后RAD51表达升高,KU70表达没有变化.结论:CKS1表达与食管癌细胞的辐射敏感性密切相关,可能通过影响DNA损伤修复发挥作用.     

自由基与应激性溃疡形成的关系

应激性溃疡是一种临床上常见的疾病,死亡率很高。其病因包括烧伤、中枢神经系统损伤、感染、败血症、创伤、手术、休克以及心、肺、肝、肾衰竭等多种疾病。研究其发生机制具有重要的理论意义和临床意义。生物氧化可为机体的代谢提供能量,因此,需氧生物离不开氧。但在生物氧化过程中,机体也可产生一些与氧有关的自由基。如超氧自由基(superoxide free radical,O_2)氢氧自由基(hy-droxyi free radical,OH)等。而这些自由基对机体往往是有害的。如自由基可与生物膜磷脂分子中的多不饱和脂肪酸发生过氧化作用,从而破坏     

白杨不同倍花粉的辐射敏感性及其应用

通过对白杨二倍性未减数花粉和单倍性花粉萌发率和萌发进程的面容统计,证明不同倍性花粉对＾６０Ｃｏγ射线辐射的敏感性不同,其中单倍性花粉的敏感性约为二倍花粉的２倍。为克服二倍性花粉在参与受精过程中萌发迟缓、竞争能力较差的问题,可利用这种花粉倍性对辐射的敏感性差异,施加一定剂量的辐射以刺激二倍性花粉萌发,同时抑制或杀死部分单倍性花粉,从而在一定程度上相对提高柱头上萌发和萌发较快的二倍性花粉比率。三倍体育     

丹参不同生长时期对UV-B辐射的敏感性

以遮阳棚下盆栽药用植物丹参为研究材料,以综合了株高、叶面积和生物量3个形态学指标的敏感性指数SI以及叶片中主要酚酸类物质迷迭香酸(RA)和丹酚酸B(SAB)含量为指标,研究快速生长期和收获期丹参对不同UV-B辐射强度的敏感性差异.结果表明: 随着UV-B辐射增强,敏感性指数SI在快速生长期和收获期均减小,且收获期小于快速生长期;叶片中RA和SAB含量随UV-B辐射增强而增加,收获期的变化幅度大于快速生长期.根部RA和SAB含量在UV-B辐射下减少,且随辐射强度和辐射时间延长而降低,尤其在收获期高强度UV-B处理下,RA和SAB总量分别为对照的10.0%和6.3%.     

离子注入加速棉花陆海杂种农艺性状遗传稳定性的研究

利用３０ＫｅＶ的Ｎ＾＋离子束注入陆地棉和海岛棉的花粉及杂交Ｆ１种子,分析了杂种后代农艺性状遗传稳定性的变化。结果表明：Ｎ＾＋离子辐照能显著地加速杂种后代的遗传稳定性,Ｆ４Ｍ４代性状稳定度可达９０％左右。Ｆ１种子辐照后代农艺性状多偏向陆地棉,而且花粉辐照杂交后代农艺性状表现出偏母遗传。同时以＾６０Ｃｏγ射线效应为对照,初步探讨了Ｎ＾＋离主入加速遗传稳定的机制。     

Conformation and dynamics changes of bacteriorhodopsin and its D85N mutant in the absence of 2D crystalline lattice as revealed by site-directed C NMR

¹³C NMR spectra of [3-¹³C]Ala- and [1-¹³C]Val-labeled D85N mutant of bacteriorhodopsin (bR) reconstituted in egg PC or DMPC bilayers were recorded to gain insight into their secondary structures and dynamics. They were substantially suppressed as compared with those of 2D crystals, especially at the loops and several transmembrane α_II-helices. Surprisingly, the ¹³C NMR spectra of [3-¹³C]Ala-D85N turned out to be very similar to those of [3-¹³C]Ala-bR in lipid bilayers, in spite of the presence of globular conformational and dynamics changes in the former as found from 2D crystalline preparations. No further spectral change was also noted between the ground (pH 7) and M-like state (pH 10) as far as D85N in lipid bilayers was examined, in spite of their distinct changes in the 2D crystalline state. This is mainly caused by that the resulting ¹³C NMR peaks which are sensitive to conformation and dynamics changes in the loops and several transmembrane α_II-helices of the M-like state are suppressed already by fluctuation motions in the order of 10⁴-10⁵ Hz interfered with frequencies of magic angle spinning or proton decoupling. However, ¹³C NMR signal from the cytoplasmic α-helix protruding from the membrane surface is not strongly influenced by 2D crystal or monomer. Deceptively simplified carbonyl ¹³C NMR signals of the loop and transmembrane α-helices followed by Pro residues in [1-¹³C]Val-labeled bR and D85N in 2D crystal are split into two peaks for reconstituted preparations in the absence of 2D crystalline lattice. Fortunately, ¹³C NMR spectral feature of reconstituted [1-¹³C]Val and [3-¹³C]Ala-labeled bR and D85N was recovered to yield characteristic feature of 2D crystalline form in gel-forming lipids achieved at lowered temperatures.     

^15N标记稻草中N,C在羊体内的转化和利用

应用~(13)N标记稻草饲喂3只山羊,以探明羊对稻草N、C化合物的消化、吸收、排泄和转化规律。结果表明,已宰杀的2只羊消化、吸收、转化为羊机体的~(15)N占试验日粮中~(15)N富集总量的38.54和23.78％,平均为31.16％。3只羊从粪尿中排泄的~(15)N各占饲料中~(15)N的34.78、33.88和33.18％,平均为33.95±0.80％,已屠宰的2只羊对饲料~(15)N总回收率为73.32和56.96％,损失率为26.68和43.04％。饲料~(15)N的回收利用率与饲料中氨基酸的消化率(％)相吻合。1、2、3号羊对饲料碳水化合物的消化率分别为76.40、68.66和65.19％。其中饲喂2、3号羊的饲料中都含稻草50％左右,羊对碳水化合物的平均消化率为66.93％。     

Sphaeropsidins D and E, two other pimarane diterpenes, produced in vitro by the plant pathogenic fungus Sphaeropsis sapinea f. sp. cupressi

Two pimarane diterpenes structurally related to sphaeropsidins were isolated from the liquid culture of Sphaeropsis sapinea f. sp. cupressi, a plant pathogenic fungus causing a form of canker disease of Italian cypress (Cupressus sempervirens L.). The two metabolites, characterised by spectroscopic methods, were named sphaeropsidins D (0.40 mg l(-1)) and E (0.16 mg l(-1)). The same fungus produced sphaeropsidins A, B and C, sphaeropsidone and episphaeropsidone, which proved to be phytotoxic to cypress, and chlorosphaeropsidone and epichlorosphaeropsidone showing no phytotoxicity. Sphaeropsidin D assayed at 0.1 mg ml(-1) on severed cypress twigs caused leaf browning and necrosis on Cupressus macrocarpa, but no symptoms were observed on C. sempervirens and C. arizonica. Symptoms appeared in a period of time (6 days after toxin-treatment) shorter than that for sphaeropsidin A. Sphaeropsidin E assayed at 0.2 mg ml(-1) did not produce any symptom on the same cypress species tested with sphaeropsidin D.     

Protonation and hydrogen bonding of Ca2+ site residues in the E2P phosphoenzyme intermediate of sarcoplasmic reticulum Ca2+-ATPase studied by a combination of infrared spectroscopy and electrostatic calculations

Protonation of the Ca²⁺ ligands of the SR Ca²⁺-ATPase (SERCA1a) was studied by a combination of rapid scan FTIR spectroscopy and electrostatic calculations. With FTIR spectroscopy, we investigated the pH dependence of CO bands of the Ca²⁺-free phosphoenzyme (E2P) and obtained direct experimental evidence for the protonation of carboxyl groups upon Ca²⁺ release. At least three of the infrared signals from protonated carboxyl groups of E2P are pH dependent with pK_a values near 8.3: a band at 1758 cm⁻¹ characteristic of nonhydrogen-bonded carbonyl groups, a shoulder at 1720 cm⁻¹, and part of a band at 1710 cm⁻¹, both characteristic of hydrogen-bonded carbonyl groups. The bands are thus assigned to H⁺ binding residues, some of which are involved in H⁺ countertransport. At pH 9, bands at 1743 and 1710 cm⁻¹ remain which we do not attribute to Ca²⁺/H⁺ exchange. We also obtained evidence for a pH-dependent conformational change in β-sheet or turn structures of the ATPase. With MCCE on the E2P analog E2(), we assigned infrared bands to specific residues and analyzed whether or not the carbonyl groups of the acidic Ca²⁺ ligands are hydrogen bonded. The carbonyl groups of Glu⁷⁷¹, Asp⁸⁰⁰, and Glu⁹⁰⁸ were found to be hydrogen bonded and will thus contribute to the lower wave number bands. The carbonyl group of some side-chain conformations of Asp⁸⁰⁰ is left without a hydrogen-bonding partner; they will therefore contribute to the higher wave number band.     

Modelling O2 and O2 unidirectional fluxes in plants. III: Fitting of experimental data by a simple model

Photosynthetic assimilation of CO₂ in plants results in the balance between the photochemical energy developed by light in chloroplasts, and the consumption of that energy by the oxygenation processes, mainly the photorespiration in C₃ plants. The analysis of classical biological models shows the difficulties to bring to fore the oxygenation rate due to the photorespiration pathway. As for other parameters, the most important key point is the estimation of the electron transport rate (ETR or J), i.e. the flux of biochemical energy, which is shared between the reductive and oxidative cycles of carbon. The only reliable method to quantify the linear electron flux responsible for the production of reductive energy is to directly measure the O₂ evolution by ¹⁸O₂ labelling and mass spectrometry. The hypothesis that the respective rates of reductive and oxidative cycles of carbon are only determined by the kinetic parameters of Rubisco, the respective concentrations of CO₂ and O₂ at the Rubisco site and the available electron transport rate, ultimately leads to propose new expressions of biochemical model equations. The modelling of ¹⁸O₂ and ¹⁶O₂ unidirectional fluxes in plants shows that a simple model can fit the photosynthetic and photorespiration exchanges for a wide range of environmental conditions. Its originality is to express the carboxylation and the oxygenation as a function of external gas concentrations, by the definition of a plant specificity factor Sp that mimics the internal reactions of Rubisco in plants. The difference between the specificity factors of plant (Sp) and of Rubisco (Sr) is directly related to the conductance values to CO₂ transfer between the atmosphere and the Rubisco site. This clearly illustrates that the values and the variation of conductance are much more important, in higher C₃ plants, than the small variations of the Rubisco specificity factor. The simple model systematically expresses the reciprocal variations of carboxylation and oxygenation exchanges illustrated by a “mirror effect”. It explains the protective sink effect of photorespiration, e.g. during water stress. The importance of the CO₂ compensation point, in classical models, is reduced at the benefit of the crossing points Cx and Ox, concentration values where carboxylation and oxygenation are equal or where the gross O₂ uptake is half of the gross O₂ evolution. This concept is useful to illustrate the feedback effects of photorespiration in the atmosphere regulation. The constancy of Sp and of Cx for a great variation of P under several irradiance levels shows that the regulation of the conductance maintains constant the internal CO₂ and the ratio of photorespiration to photosynthesis (PR/P). The maintenance of the ratio PR/P, in conditions of which PR could be reduced and the carboxylation increased, reinforces the hypothesis of a positive role of photorespiration and its involvement in the plant-atmosphere co-evolution.