肠浒苔多糖的羧甲基化修饰及其抗氧化活性研究

该研究采用氢氧化钠-氯乙酸的化学反应体系制备羧甲基化肠浒苔多糖,以获得不同取代度的羧甲基化肠浒苔多糖,取代度的大小受氢氧化钠浓度、反应温度和反应时间的影响。结果表明:(1)当氢氧化钠浓度20%、反应温度60℃、反应时间3 h时,得到羧甲基化的最大取代度为0.781。(2)通过体外抗氧化来评价不同羧甲基化肠浒苔多糖的抗氧化活性。(3)当羧甲基化肠浒苔多糖的浓度为1.6 mg·mL~(-1)时,羧甲基化肠浒苔多糖清除羟基自由基、超氧阴离子自由基的能力分别为44.45%、51.98%,其清除DPPH自由基清除率和还原能力分别为16.75%、0.457 6。(4)与修饰前的相比,羟基自由基、超氧阴离子的清除能力均有较大幅度提高,羧甲基化修饰对肠浒苔多糖的DPPH自由基和还原力有减弱作用。以上结果表明,羧甲基化修饰引起的肠浒苔多糖的结构变化可以提高其抗氧化活性。     

不同光照条件下外源水杨酸对浒苔响应紫外辐射胁迫的影响

为研究不同光照条件下,外源水杨酸(SA)和紫外辐射(UV)对海洋绿藻浒苔的复合效应,在两个光照强度(高光:160 μmol·m^-2·s^-1;低光:70 μmol·m^-2·s^-1)条件下,设置对照(CK)、SA、UV及UV+SA处理(UV=3.2 W·m^-2、SA=10 μg·mL^-1),处理3 d后测定浒苔生长、叶绿素荧光参数、光合放氧速率、超氧化物歧化酶活性、可溶性糖和可溶性蛋白含量等的变化,探讨光照强度、UV及SA的复合效应.结果表明: 低光无UV条件下,SA会促进浒苔生长,降低浒苔叶绿素a(Chl a)和可溶性蛋白含量;高光无UV条件下, SA会抑制其生长,但显著提高了Chl a含量、呼吸速率、光合放氧速率、可溶性糖和可溶性蛋白含量;高光和UV条件下, UV+SA显著促进浒苔生长,提高Chl a和可溶性糖含量;低光和UV条件下,与UV相比,UV+SA提高了浒苔最大光化学效率(F_v/F_m)和可溶性蛋白含量,涨幅分别为139.8%和32.2%.外源SA的加入在一定程度上缓解了UV对浒苔的胁迫作用,且在高光条件下的效果更为显著.     

大型绿藻浒苔转化表达系统选择标记的筛选

主要研究了条浒苔对抗生素氯霉素和除草剂Basta的敏感性,以确定适合的阳性选择标记基因。应用不同浓度氯霉素(0、25、50、75、100、125μg/ml)和Basta(0、5、12.5、25、37.5、50μg/ml)对不同发育时期条浒苔细胞存活率影响进行了测定。实验结果表明:不同发育时期条浒苔对氯霉素和Basta的敏感性不同。其中最大浓度125μg/ml浓度的氯霉素在15d内对条浒苔孢子和小苗两个不同发育时期的细胞均难以达到全部杀死效果,相对存活率仍分别为1%和20%;而Basta对条浒苔孢子和小苗均具有很强的杀生作用,其中5μg/ml浓度的Basta在3d内可将条浒苔孢子全部杀死,12.5μg/ml浓度下约一周时间可以将浒苔小苗全部致死。本实验结果提示bar基因有可能成为浒苔基因工程较理想的选择标记基因。     

Al_2O_3催化剂对海洋生物质热解特性的影响

以海洋生物质浒苔为研究对象,并以玉米秸秆(草类生物质)和锯末(木质类生物质)为对照,采用热重分析方法研究了3种生物质的热解特性,并比较了3种生物质之间的热解差异。结果表明,与玉米秸秆和锯末等典型陆生生物质相比,浒苔的热稳定性最低。此外,以不同浓度氧化铝作为催化剂,用热重分析法对其热解过程进行了研究,利用TG-DTG曲线分析了不同催化剂在不同浓度下对其基本热解特性的影响。结果表明,Al2O3对于3种生物质转化率和最大失重速率有显著的影响,其中Al2O3对锯末和浒苔的转化率降低程度比玉米秸秆较明显。考虑到Al2O3具有可调变的表面酸碱性以及多种不同的晶相结构等优点,Al2O3具有较大的的应用价值。     

条浒苔和缘管浒苔对镉胁迫的生理响应比较

为探讨大型海藻对重金属胁迫的生理响应及耐受机制,以条浒苔（Enteromorpha clathrata）和缘管浒苔（Enteromorpha linza）为试验材料,研究了不同浓度的镉（Cd2 ）处理7天对两个浒苔品种的生长、叶绿素（Chl）和类胡萝卜素（Car）含量、叶绿素荧光参数以及可溶性糖（SS）和可溶性蛋白含量（SP）的影响。结果表明：随着Cd2 浓度的增加,条浒苔和缘管浒苔鲜重和相对生长速率（RGR）与对照相比显著下降,且条浒苔的鲜重和RGR降低幅度大于缘管浒苔。镉胁迫下,叶绿素和类胡萝卜素含量、叶绿素a/叶绿素b（Chla/Chlb）、PSⅡ最大光能转化效率（Fv/Fm）、PSⅡ实际光能转化效率（Yield）、最大相对电子传递速率（rETRmax即Pm）和光能利用效率（α）、可溶性蛋白含量随着Cd2 浓度的升高均出现下降趋势,除了叶绿素外,条浒苔的其它指标的降幅要大于缘管浒苔。随着镉胁迫强度的增加,浒苔可溶性糖含量呈现逐渐显著上升。上述表明,条浒苔和缘管浒苔对Cd2 胁迫均具有一定的适应能力,且缘管浒苔耐镉性高于条浒苔。在镉胁迫下,维持较高的Car含量、Chla/Chlb、Fv/Fm、Yield、rETRmax、α、SS含量、SP含量是缘管浒苔耐镉性高于条浒苔的主要原因。     

科研快讯

《植物与细胞生理学》:研究阐明浒苔对环境胁迫响应分子机制近日,中国科学院海洋研究所的研究人员在浒苔生物学研究取得重要进展,阐明了浒苔对环境胁迫响应的分子机制和"绿潮"发生时漂浮浒苔的生理状,为全面认识由浒苔引发的海洋"绿潮"现象提供了重要理论基础。相关研究成果发表在在国际期刊《植物     

水杨酸对浒苔生长和生理特性的影响

为探讨水杨酸(SA)对不同增殖方式来源的浒苔生长和生理特性的影响,本文选取营养繁殖得到的浒苔(VU)和孢子/配子繁殖得到的浒苔(SU)作为供试材料,设置不同的水杨酸浓度,测定两种浒苔的生长、叶绿素荧光、超氧化物歧化酶(SOD)和可溶性蛋白含量等生理指标.结果表明: 低浓度水杨酸可以促进VU和SU的生长,对VU促进效果更为显著;在0.2 μg·mL^-1水杨酸浓度下,VU相对生长速率达到最大值21.0%,且与SU相比,VU最大光化学效率提高了9.8%.水杨酸对两种浒苔的SOD活性影响较大,在水杨酸浓度为0.2、0.5 μg·mL^-1下,VU的SOD活性增幅分别达52.0%、198.6%,SU的SOD活性增幅分别达54.1%、38.0%.水杨酸促进了浒苔的相对电子传递速率、光合作用和蛋白质含量.水杨酸对两种增殖方式来源的浒苔的生长均有促进作用,尤其是对VU的促进作用更为明显.     

秀丽隐杆线虫对不同氧浓度的应答及其调控机制研究进展

不同地理位置的人类生活环境中氧气水平不同,与人体的正常生理功能密切相关。体内氧气的减少会引发多种疾病,如大脑缺血、缺氧导致的脑卒中。近年来利用秀丽隐杆线虫(Caenorhabditis elegans,简称线虫)作为模式生物研究机体对不同氧浓度应答和调控机制取得了长足进展。研究表明,线虫会逃避氧浓度过高或过低的环境,并对周围氧气浓度的变化有适应性,而且其在不同程度低氧环境中存在不同的应答与调控机制。本文综述了近年来线虫对不同氧气浓度的反应和调控机制研究进展。     

《植物与细胞生理学》：研究阐明浒苔对环境胁迫响应分子机制

近日,中国科学院海洋研究所的研究人员在浒苔生物学研究取得重要进展,阐明了浒苔对环境胁迫响应的分子机制和“绿潮”发生时漂浮浒苔的生理状,为全面认识由浒苔引发的海洋”绿潮”现象提供了重要理论基础。相关研究成果发表在在国际期刊《植物与细胞生理学》（Plantand Cell Physiology）上。     

两种浒苔无机碳利用对温度响应的机制

为了探讨温度对大型海藻无机碳利用机制的影响,选择了潮间带常见的绿藻缘管浒苔 （Ulva linza）和浒苔（Ulva prolifera）为实验材料,研究了碳酸酐酶抑制剂乙酰唑磺胺（AZ）和己氧苯并噻唑磺胺（EZ）在不同的温度下对藻体光合作用的影响。实验设置6个温度梯度（5、10、15、20、25和30℃）。结果表明,缘管浒苔和浒苔都有很强的无机碳利用能力,而温度对此有显著的影响。但他们之间存在明显的种间差异。缘管浒苔对温度的依赖性要强于浒苔,其对温度的适应范围要窄于浒苔,尤其是在高温下（30℃）,缘管浒苔的最大光合作用能力与最适温度相比下降了56%,而浒苔仅为20%,这表明在高温的情况下,浒苔比缘管浒苔具有更强的生存适应能力,这是浒苔能够在绿潮藻占有绝对优势的原因之一。对缘管浒苔来说,在低温（5℃）和高温（30℃）时,无机碳的转运主要是通过胞外碳酸酐酶的催化作用,而在15℃时,加入胞外碳酸酐酶的抑制剂对无机碳的转运没有明显的影响,这表明在此温度下其他无机碳转运形式可以有效补偿胞外碳酸酐酶的作用。在其他的温度下,胞外碳酸酐酶和其他无机碳转运方式各占一定的比例。而对于浒苔来说,在低温5℃时,其他无机碳转运形式占主要作用,而从10℃开始,胞外碳酸酐酶作用比例显著增加,并且保持在相同的水平上。     

Physiological, biochemical, and mathematical studies of micro-aerobic continuous ethanol fermentation by Saccharomyces cerevisiae. I: hysteresis, oscillations, and maximum specific ethanol productivities in chemostat culture

The growth and metabolism of Saccharomyces cerevisiae was studied in steady-state chemostat cultures under conditions of scarce oxygen and excess glucose. The specific ethanol productivity and specific glucose uptake rate were stimulated by 50% within a narrow range of air/nitrogen mixtures to the fermentor. Fermentation was inhibited at slightly higher and lower air/nitrogen ratios, confirming similar results by previous investigators. This stimulation could not be caused by obvious mechanisms, such as the Pasteur or Crabtree effects. Since this maximum in the fermentation rate occurred in a steady-state chemostat and at a constant dilution rate, the ATP yield of the culture necessarily attained a minimum. Thus, changes in the energetic efficiency of growth or the degree of wasting of ATP were surmised. The steady-state biomass concentration at various oxygenation rates exhibited hysteresis phenomena. Ignition and extinction of the biomass concentration occurred as critical oxygen feed rates were passed. The hysteresis was prevented by adding yeast extract to or reducing the antifoam concentration in the medium. These medium alterations had the simultaneous effect of stimulating the fermentation rate, suggesting that ATP has a critical role in dictating the biomass concentration in micro-aerobic culture. Silicone polymer antifoam was found to stimulate glycerol production at the expense of ethanol production, having consequences for the energy generation and the biomass concentration of the culture.     

坛紫菜叶状体的无菌化培养及其应用

对坛紫菜叶状体的无菌处理方法进行了优化,并利用紫菜外生菌对无菌处理后的紫菜叶片进行了人工感染。经0.7%KI和0.1%(w/v)氨苄青霉素对紫菜叶片进行预处理后,利用氨苄青霉素、硫酸链霉素、新霉素、庆大霉素及卡那霉素等5种抗生素及其不同组合对紫菜叶片进行处理,筛选出最佳抗生素组合、浓度和培养条件。结果表明:氨苄青霉素(终浓度300μg/mL)、卡那霉素(终浓度100μg/mL)与庆大霉素(终浓度100μg/mL)3种抗生素组合对坛紫菜叶状体进行无菌处理18 h,对紫菜细胞的毒害较小,并且3种抗生素合用对89.5%紫菜外生细菌的抑菌率达80%以上;外生菌感染结果研究表明:用105/mL真菌孢子液和细菌菌液回染紫菜,培养22 d后,实验组紫菜生长状况较对照组好,对照组紫菜出现褪色。用108/mL真菌孢子液分别回染健康紫菜、穿刺紫菜(用灭菌刀片在紫菜表面划1～2 mm的伤口),分别在18℃、28℃和35℃条件下培养。实验结果表明28℃和35℃高温和穿刺均会影响无菌紫菜健康生长,且加菌紫菜在高温和穿刺条件下,则会出现明显病斑,而18℃培养的加菌紫菜则生长良好。     

A generalized theory of the transition time for sequential enzyme reactions.

In a sequence of coupled enzyme reactions the steady-state production of product is preceded by a lag period or transition time during which the intermediates of the sequence are accumulating. Provided that a steady state is eventually reached, the magnitude of this lag may be calculated, even when the differentiation equations describing the process have no analytical solution. The calculation may be made for simple systems in which the enzymes obey Michaelis-Menten kinetics or for more complex pathways in which intermediates act as modifiers of the enzymes. The transition time associated with each intermediate in the sequence is given by the ratio of the appropriate steady-state intermediate concentration to the steady-state flux. The theory is also applicable to the transition between steady states produced by flux changes. Application of the theory to coupled enzyme assays allows a definition of the minimum requirements for successful operation of the assay. The theory can be extended to deal with sequences in which the enzyme concentration exceeds substrate concentration.     

Relationship between a metabolic rhythm and emergence rhythm in Drosophila melanogaster

Oxygen consumption and lactic acid dehydrogenase (LDH) activity were determined for Drosophila melanogaster pupae and pharate adults exposed to 12 : 12 or 1 : 23 light-dark (LD) regime. Bimodal circadian fluctuations of oxygen consumption were found in pupae and pharate adults exposed to either LD regime and organisms appeared to demonstrate an anticipatory change in oxygen consumption associated with change in illumination. The oxygen-consumption trend for the entire period spent in the puparium showed a high at the time of emergence, but the diurnal rhythm showed a low at the time of emergence suggesting that emergence occurs at a low in the diurnal cycle. Emergence maximum showed a 3 hr lead over the oxygen-consumption maximum. Changing the LD regime produced similar changes in the phasing of both oxygen consumption and emergence rhythms. LDH activity did not demonstrate a detectable circadian rhythm but did show a steady decrease during pupal and pharate adult development.     

Spatial variation in carbon isotope discrimination across the thalli of several lichen species

Variations in stable carbon isotope discrimination (δ) were investigated across the thalli of several lichen species possessing different photobiont associations. Lichens containing (i) green algae (phycobiont), (ii) green algae in association with cyanobacteria confined in cephalodia, or (iii) cyanobacteria (cyanobiont) as the photobiont partner were studied. Carbon isotope discrimination was analysed in different thallus sections, which varied in distance from the margin and in age. The marginal thallus region is considered to be youngest, while the central region is thought to be oldest. This analysis showed a clear variation in δ across the thallus related to distance from the growing margin. In most of the species examined, the highest δ values were found in marginal regions (younger), while the central and basal regions (older) showed significantly lower δ. To investigate the effects of the historical increase in atmospheric CO₂ concentration and the concurrent decrease in the ¹³C content of atmospheric CO₂ on the δ of lichens, experiments were carried out on herbarium samples of Lobaria pulmonaria collected from the mid 19th Century to 1953. The results obtained showed a pattern of variation of δ consistent with that of freshly collected samples; δ decreased substantially with increasing distance from the thallus margin, irrespective of the collection date. Moreover, no consistent variation of discrimination was found among different collection dates. These results demonstrate that the observed variation in δ is caused by age-related changes in the physiological behaviour of different thallus sections, and that the past 150 years of increasing CO₂ concentration have not had significant effects on A in L. pulmonaria. Photosynthesis measurements, chlorophyll analysis and observations using optical microscopy, performed on freshly collected lichens, showed significant changes in morphological and physiological characteristics across the thallus. Particularly, remarkable variations in thickness were found across the thallus. These anatomical changes may be responsible for the variation in δ, through variations in CO2 transfer resistance and, consequently, in CO₂ availability across the thallus. The lack of age-dependent variation in δ in cyanobiont lichens is possibly attributable to the operation of a CO₂-coneentrating mechanism and, therefore, to a more constant CO₂ environment across the thallus in this lichen group.     

Xenobiotic substrate reduces yield of activated sludge in a continuous flow system

The biomass yield of a continuous flow activated sludge system varied when the system treated influent containing different compositions of biogenic and xenobiotic substrates. Both the biogenic substrate and a test xenobiotic 2,4-dichlorophenoxyacetic acid (2,4-D) were degraded at steady-state activated sludge operations. The true yields, determined from steady-state activated sludge treatment performances, were at the maximum and the minimum when the activated sludge treated the influent of sole biogenic substrate and sole 2,4-D, respectively. The minimum yield was 56% of the maximum. Yield reduction between the maximum and the minimum was proportional to the concentration of 2,4-D in the influent. This trend of yield reduction suited a model that describes the metabolic uncoupling effect of 2,4-D on the sludge's degradation of the substrates. The model function variable was defined as the ratio of 2,4-D to biogenic COD concentrations in the influent.     

水稻叶片Rubisco 活化酶表达的昼夜变化

在 48h的自然光照、连续光照和连续黑暗处理下 ,水稻幼苗rcamRNA的含量均表现出昼夜节奏特性 ,其中以自然光周期中变化最为明显。在光暗交替的条件下 ,RCA含量虽也表现出明显的昼夜变化 ,但连续黑暗处理其含量持续下降 ,连续光照则其含量先上升然后下降 ,说明它不发生节昼现象。这些结果表明RCA表达在转录和翻译水平上的调控机制不同 ,转录既由光暗交替控制又受内生节奏调节 ,而翻译则更大程度上由光调节     

Seasonal variations in thalli and carrageenan composition of Gigartina pistillata (Gmelin) Stackhouse (Rhodophyta, Gigartinales) harvested along the Atlantic coast of Morocco

The biology and biochemistry of Gigartina pistillata (Gmelin) Stackhouse collected monthly at Nation Beach (Morocco), was studied during one year. The biological study showed one period of active growth from April to July. The thallus composition was quite stable during the major part of the year. The dry matter was maximum in May and August and minimum in January. The maximum carrageenan content occurred in June and September (about 37%) and the minimum carrageenan content occurred in February (19.0%). The total nitrogen content varied significantly, with a maximum in January (1.98%) and a minimum in August (0.7%). The ash content was significant (23–32%) with a maximum in August and a minimum in May. The carrageenan extracted from natural populations of Gigartina pistillata was a mixture of lambda‐type and kappa‐type carrageenans. The 3,6‐anhydrogalactose varied between 4.5 mol% in June to 25 mol% in February. For industrial applications the extract could be considered as a lambda‐type. The best period for harvest of G. pistillata in Morocco is between July and August when biomass and viscosity are at their maximum. A relationship between the physical characteristics of G. pistillata carrageenans and its seasonal cycle was deduced.     

Range of entrainment of rat circadian rhythms to sinusoidal light-intensity cycles

The range of entrainment of the circadian behavioral rhythm was compared between two groups of Sprague-Dawley rats (each n = 10) exposed to daily cycles of rectangular light-dark alternation (LD) and sinusoidal fluctuations of light intensity (SINE), respectively. The maximum illuminance (20 lx), the minimum illuminance (0.01 lx), and the total amount of light exposure per cycle were the same under the two lighting conditions. The periods (Ts) of both lighting cycles were lengthened stepwise from 24 through 25, 26, 26.5, 27, 27. 5, and 28 h to 28.5 h in experiment 1 and were shortened stepwise from 24 through 23.5, 23, and 22.5 h to 22 h in experiment 2. Each T cycle lasted for 30 cycles. In experiment 1, 60% of rats under the LD condition entrained up to T = 28.5 h, whereas 50% of rats under the SINE condition entrained up to T = 28.5 h. In experiment 2, no animal under the LD condition entrained to T < 23.5 h, whereas 40% of rats under the SINE condition entrained down to T = 23 h and 20% of rats remained to entrain down to T = 22 h cycles. The phase angle of entrainment was systematically changed, depending on T under both conditions. These results suggest that the lower limit of entrainment is expanded under the SINE condition compared with the LD condition.