植物中的氯、氯通道和耐氯性

本文介绍了氯(Cl)在自然界的存在形式,Cl与植物生长发育的关系及植物对Cl-的吸收和运输机制。概述了Cl-通道和Cl-通道蛋白(CLCs)的种类与特点。探讨了不同植物对Cl-亏缺、过量的不同响应及植物耐Cl-的可能生理和分子生物学机制。     

TMEM16/ANOCTAMIN:最新的氯通道家族

Cl-通道参与许多生理过程,包括跨上皮细胞的离子吸收与分泌、平滑肌与骨骼肌收缩、神经元兴奋性、器官感知功能及细胞容积调节等.目前对于许多类型Cl-通道的分子构型尚不清楚.新近三个独立的研究小组同时发现Ano1是一种与钙离子激活氯通道(calcium-activated chloridechannels,CaCCs)活性密切相关的膜蛋白.Ano1与其它9个成员共同组成Anoctamin家族.所有Anoctamin蛋白都具有类似结构,推测含8个跨膜结构域以及胞质N-末端和C-末端.Ano1和Ano2的表达都与CaCCs类似,但其它Anoctamin蛋白的作用仍然未知.     

长期施用含氯化肥对稻田土壤氯积累及养分平衡的影响

随着含氯化肥 (氯化钾和氯化铵 )在中国的广泛施用 ,其对稻田生态系统的长期影响成为人们关心的问题。为此 ,1975年在湖南祁阳红壤站建立了含氯化肥长期定位试验 ,3个处理 (CK、低氯和高氯 )的施 Cl量分别为 0、35 2、10 32 kg/ (hm2· a) ,其历年土壤样品和 1997年水稻植株样品被用于研究长期连续施用氯化钾和氯化铵后 Cl-在土壤 -水稻系统中的累积及其对土壤养分平衡和水稻养分吸收的影响。结果表明 :Cl- 极易随水淋失 ,在土壤中的总残留率极低 (占总施氯量的 0 .16 %～ 0 .2 1% ) ,但长期的积累还是使施氯处理土壤 Cl- 含量显著增加 ,连续施用高氯化肥 2 4 a后 (1998) ,表土 (0～ 2 0 cm)中的 Cl- 含量比试验前(1975 )增长了 5 2 .2 % ,0～ 10 0 cm土壤剖面中和稻草中的 Cl-含量也显著增加 ;长期施用高氯化肥使表土中有效 K、Cu、B、Mn及全 Ca含量显著降低 ,而剖面 (6 0～ 80 cm)中的有效 B显著增加 ,对土壤有机质、全 N、全 P、有效 Mo、Zn及总 Mg没有明显影响 ;长期施用高氯化肥还显著抑制早稻对 P、Ca、Mn、Cu的吸收和晚稻对 Ca、Mn、Cu、Si的吸收 ,促进水稻对 Cl和 Zn的奢侈吸收 ,妨碍早稻植株中的 P、Cu和晚稻植株中的 Cu、Zn、Si向籽粒运输 ,使这些元素在稻谷中的分配率显著降低。长期施用低氯     

ATP激活鼻咽癌细胞氯电流并减小细胞容积

采用全细胞膜片钳技术和细胞容积测量技术,在低分化鼻咽癌细胞株CNE-2Z上观察ATP 诱导的Cl- 电流的特性及其对细胞容积的影响。细胞外微摩尔水平的ATP 以剂量依赖性的方式激活一个具有弱外向整流特性,没有时间依赖性失活的电流,此电流的反转电位 [(-0.05 ± 0.03) mV]接近Cl- 的平衡电位(-0.9 mV)。用葡萄糖酸置换细胞外液Cl- 后, ATP 激活的电流明显减小并且反转电位发生改变。氯通道抑制剂NPPB (200 μmol/L)可以抑制这一电流 [(81.03 ± 9.3)%] 。此电流亦可被嘌呤受体(P2Y) 拮抗剂反应蓝 2 抑制 [(67.39 ± 5.06)%]。50 μmol/L 的 ATP 使在等渗状态下的细胞容积缩小, 替代和耗竭细胞外、内的Cl- 后, ATP 的这一作用消失。这些结果提示细胞外微摩尔水平的 ATP 可通过兴奋 P2Y 受体激活氯通道而产生与细胞容积调节相关的Cl- 电流。     

Ca2+激活Cl-通道功能及分子基础研究进展

自从1983年Barish在爪蟾卵母细胞中发现钙激活的Cl–通道以来,此种类型Cl–通道一直在被广泛的研究,其在不同组织中的重要作用也被不断报道。但是,钙激活氯电流的分子机制一直未被阐明。直到2008年,由三个实验室分别发现了构成钙激活Cl–通道的分子基础为跨膜蛋白16A(transmembrane protein 16A,TMEM16A),这一发现使得人为通过基因手段调控钙激活Cl–通道的功能与表达成为可能。该文综述了钙激活Cl–通道在不同组织中的作用、TMEM16A的电生理和药理学特性以及TMEM16A在心肌肥厚和心衰中的可能作用,以及以Cl–通道作为药物作用靶点的研究进展。     

短杆菌肽A-DMPC通道内离子输运的分子动力学模拟

用最近提出的构建膜体系初始构象的有效方法 ,构建了在DMPC脂膜环境下短杆菌肽A通道模型 (GA -DMPC)。通过对Na 、Ca2 、Cl-三种不同离子在GA -DMPC通道内不同位置的分子动力学模拟 ,研究离子在通道内输运过程中与通道及通道内水分子的相互作用 ,从分子动力学的角度阐明离子在通道内的输运机制。主要计算结果表明 :(1)离子在通道内的输运使GA的构象发生变化 ,GA的柔性是离子在通道内通透的重要因素 ;(2)Cl- 离子可扩大通道半径 ,Na 离子和Ca2 离子则减小通道半径。Cl-离子不能在GA通道内通透 ;(3)离子的出现使通道内水分子的偶极方向发生变化。上述结果均与实验相符。     

广西红海榄红树群落的氯钠动态

本文主要探讨了广西英罗湾64年生红海榄(Rhizophora stylosa)红树群落对Cl、Na的吸收分布和生物循环。结果表明:该群落现存生物量中.库存Cl、Na总量分别为349.39g/m~2和279.8 5g/m (g·Cl/g·Na=1.25,mol·Cl/mol.Na=0.81),其中地上部分别占60.4%和5 6.9%,地下部分别占39.6%和4 3.1%。群落Cl、Na的生物循环为:年吸收量分别为40.18g/m~2和26.56g/m~2;年存留量分别为11.40g/m~2和9.15g/m~2;年归还量分别为28.78g/m~2和17.41g/m ~2;循环系数分别为0.72和0.66。周转期Cl(12年)快于Na(16年)。群落对Cl、Na的富集率分别为2.18和1.8.     

外源氯胁迫对甘薯幼苗光合特性的影响

采用温室水培方法,以甘薯品种‘徐薯22’,‘苏薯11’和‘宁紫1号’为材料,外源氯(0、42.2、84.4、168.8、211mmol.L-1)胁迫处理7d、14d和21d,测定其生理生化及气体交换参数,探讨Cl-对甘薯幼苗生长以及光合特性的影响。结果表明:(1)‘徐薯22’叶面积与主蔓生长速率受外源氯胁迫而降低但仍维持在一定水平,而‘苏薯11’和‘宁紫1号’则在低浓度Cl-(≤84.4mmol.L-1)处理下高于对照。(2)3个甘薯品种叶片净光合速率(Pn)及光合色素含量在42.2mmol.L-1 Cl-处理下均高于对照;导致‘徐薯22’光合能力降低的主要因素为非气孔限制,而‘苏薯11’和‘宁紫1号’兼有气孔限制和非气孔限制因素,在短期或低浓度Cl-处理条件下以气孔限制因素为主。(3)处理21d时,甘薯幼苗根系氯离子含量低于14d且氯离子向地上部运输比率(SCl)上升;‘徐薯22’积累Cl-含量低于‘苏薯11’和‘宁紫1号’。研究发现:外源氯低浓度短期处理利于甘薯幼苗生长及光合作用的进行;在胁迫初期甘薯可有效抑制Cl-向地上部转运,但在处理第3周该抗逆性明显减弱;甘薯对氯胁迫的耐受性存在基因型差异,本实验中以‘徐薯22’耐性较强。     

人胎儿鼻咽上皮细胞的背景氯电流

采用膜片钳和图像分析技术,研究人胎儿鼻咽上皮细胞背景电流的特性及其与容积激活性氯电流的关系。在等张溶液中,可记录到一背景电流,该电流呈微弱的外向整流性,无明显时间依赖性失活,其翻转电位为(?0.73±1.7)mV(n=21),接近氯离子平衡电位(?0.9mV)。细胞外高张刺激(440mOsmol/L)明显抑制此电流(59.6±7.1)%,而低张刺激(160mOsmol/L)则诱发细胞产生容积激活性氯电流。氯通道阻断剂tamoxifen和5-硝基-2-(3-苯丙胺基)苯甲酸[5-nitro-2-(3-phenylpropylamino)benzoicacid,NPPB]显著地抑制背景电流并使细胞基础容积增大。上述结果表明,人胎儿鼻咽上皮细胞的背景Cl?电流是背景电流的重要成分,此Cl?电流与容积激活性氯电流及细胞基础容积调节有关。     

钠盐和氯盐胁迫下胡杨木质部汁液ABA、离子浓度和叶片气体交换的变化

研究了渗透胁迫和盐胁迫下一年生胡杨(Populus euphratica Oliv.)幼苗的木质部汁液脱落酸(ABA)、离子浓度及叶片气体交换的变化.PEG 6000 (溶液渗透势 -0.24 MPa)、50 mmol/L含钠离子的盐溶液 (NaNO3∶NaHCO3∶NaH2PO4=5∶4∶1, pH 6.8, 渗透势 -0.24 MPa)和50 mmol/L含氯离子的盐溶液 (KCl∶NH4Cl=1∶1, 渗透势 -0.24 MPa) 3种处理都显著降低了苗木的净光合速率(Pn)和蒸腾速率(TRN),但盐处理植株的TRN高于PEG处理的苗木.木质部汁液ABA的浓度在PEG处理后1 h达到峰值,之后开始下降,降到对照水平后又逐渐回升.盐处理苗木的ABA也是在处理开始后就迅速升高,但之后ABA水平明显高于PEG处理的植株.结果显示,渗透胁迫和离子胁迫都能提高胡杨木质部汁液ABA的浓度: 盐处理开始后ABA的迅速升高主要是渗透胁迫的作用,而此后离子胁迫(Na+和Cl-)对ABA水平的提高具有重要作用.钠盐处理对胡杨净光合速率和蒸腾速率的抑制作用高于氯盐处理,其木质部汁液中较高水平的ABA和盐离子(Na+和Cl-)是可能的原因.钠盐处理苗木的盐离子(Na+和Cl-)水平高于氯盐处理,主要是由以下两方面的原因所致: (1)细胞膜上的Ca2+被Na+所取代, 增加了膜的透性; (2)胡杨根细胞液泡对Na+的区隔化能力较弱(与区隔Cl-相比).另外,盐胁迫下胡杨能保持对营养元素K+、Ca2+和Mg2+的吸收,这也是其抗盐性强的重要原因.     

Efficiency of Chlorine Dioxide as a Bactericide

We found chlorine dioxide to be a more effective disinfectant than chlorine in sewage effluent at pH 8.5. Chlorine dioxide was also found to be a more stable bactericide in relation to pH in the range studied.     

Chlorine, Chloramine, Chlorine Dioxide, and Ozone Susceptibility of Mycobacterium avium

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.     

Effects of Chlorine Concentration on the Structure of Poliovirus

Chlorine concentrations below 0.8 mg/liter inactivated poliovirus without causing separation of the viral components. These results indicate that the release of RNA from the capsids is the result, not the cause, of virus inactivation by chlorine.     

Chlorine Dioxide for Reduction of Postharvest Pathogen Inoculum during Handling of Tree Fruits

Alternatives to hypochlorous acid and fungicides are needed for treatment of fruit and fruit-handling facilities. Chlorine dioxide was evaluated and found effective against common postharvest decay fungi and against filamentous fungi occurring on fruit packinghouse surfaces. In vitro tests with conidial or sporangiospore suspensions of Botrytis cinerea, Penicillium expansum, Mucor piriformis, and Cryptosporiopsis perennans demonstrated >99% spore mortality within 1 min when the fungi were exposed to aqueous chlorine dioxide at 3 or 5 μg · ml^-1. Longer exposure times were necessary to achieve similar spore mortalities with 1 μg · ml^-1. Of the fungi tested, B. cinerea and P. expansum were the least sensitive to ClO₂. In comparison with the number recovered from untreated control areas, the number of filamentous fungi recovered was significantly lower in swipe tests from hard surfaces such as belts and pads in a commercial apple and pear packinghouse after treatment of surfaces with a 14.0- to 18.0-μg · ml^-1 ClO₂ foam formulation. Chlorine dioxide has desirable properties as a sanitizing agent for postharvest decay management when residues of postharvest fungicides are not desired or allowed.     

Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.     

The Life-Cycle of Chlorine, Part I: Chlorine Production and the Chlorine-Mercury Connection

Chlorine is an important industrial chemical. Not only is it a component of many important products, it is also needed for many chemical manufacturing processes, even where it does not appear in the final product. But a number of chlorine chemicals, especially organochlorines, are toxic, carcinogenic, tentogenic or otherwise potentially disturbing to the environment. For this reason, some environmentalists—notably Greenpeace-have advocated a ban, not just on some products but on all uses of elemental chlorine. The chemical industry is taking this threat seriously and mounting a vigorous defense. But the debate so far is not illuminating the issues effectively, because both sides are selectively using questionable and unverifiable data.
The scientific uncertainties are not really the problem. Rather, data in the public domain and accessible to environmentalists and even regulatory authorities are of very poor qualrty. Because of industry secrecy much crucial inforrnation is unavailable and some of what is available is misleading or wrong. The dual purposes of this article, and the ones that follow, are (I) to elucidate the information requirements for an adequate life-cycle analysis of chlorine and its uses and (2) to indicate how and where the use of massbalance methodology can help identify errors and fill in gaps.
The present article deals with electrolytic chlorine produdion and mercury flows arising from chlorine production. Subsequent articles deal with conversion processes and losses and further chemical industry uses of chlorine, major end uses of chlorine and chlorine chemicals, and persistent organochlorine pollutants.     

Inactivation Kinetics and Mechanism of a Human Norovirus Surrogate on Stainless Steel Coupons via Chlorine Dioxide Gas

Acute gastroenteritis caused by human norovirus is a significant public health issue. Fresh produce and seafood are examples of high-risk foods associated with norovirus outbreaks. Food contact surfaces also have the potential to harbor noroviruses if exposed to fecal contamination, aerosolized vomitus, or infected food handlers. Currently, there is no effective measure to decontaminate norovirus on food contact surfaces. Chlorine dioxide (ClO₂) gas is a strong oxidizer and is used as a decontaminating agent in food processing plants. The objective of this study was to determine the kinetics and mechanism of ClO₂ gas inactivation of a norovirus surrogate, murine norovirus 1 (MNV-1), on stainless steel (SS) coupons. MNV-1 was inoculated on SS coupons at the concentration of 10⁷ PFU/coupon. The samples were treated with ClO₂ gas at 1, 1.5, 2, 2.5, and 4 mg/liter for up to 5 min at 25°C and a relative humidity of 85%, and virus survival was determined by plaque assay. Treatment of the SS coupons with ClO₂ gas at 2 mg/liter for 5 min and 2.5 mg/liter for 2 min resulted in at least a 3-log reduction in MNV-1, while no infectious virus was recovered at a concentration of 4 mg/liter even within 1 min of treatment. Furthermore, it was found that the mechanism of ClO₂ gas inactivation included degradation of viral protein, disruption of viral structure, and degradation of viral genomic RNA. In conclusion, treatment with ClO₂ gas can serve as an effective method to inactivate a human norovirus surrogate on SS contact surfaces.     

Chlorine dioxide disinfection of single and dual species biofilms, detached biofilm and planktonic cells

Disinfection efficacy testing is usually done with planktonic cells or more recently, biofilms. While disinfectants are much less effective against biofilms compared to planktonic cells, questions regarding the disinfection tolerance of detached biofilm clusters remain largely unanswered. Burkholderia cepacia and Pseudomonas aeruginosa were grown in chemostats and biofilm tubing reactors, with the tubing reactor serving as a source of detached biofilm clusters. Chlorine dioxide susceptibility was assessed for B. cepacia and P. aeruginosa in these three sample types as monocultures and binary cultures. Similar doses of chlorine dioxide inactivated samples of chemostat and tubing reactor effluent and no statistically significant difference between the log(10) reductions was found. This contrasts with chlorine, shown previously to be generally less effective against detached biofilm particles. Biofilms were more tolerant and required chlorine dioxide doses ten times higher than chemostat and tubing reactor effluent samples. A second species was advantageous in all sample types and resulted in lower log(10) reductions when compared to the single species cultures, suggesting a beneficial interaction of the species.