碳酸酐酶对CO2液相扩散的影响及其与C3植物光合作用的关系

当CO_2进入水溶液时,必然存在CO_2 H_2O?H~ HCO_3~-平衡。根据Henderson-Hasselbach方程pH=pK lg[HCO_3~-]/[CO_2],平衡时溶液中CO_2和HCO_3~-浓度比由溶液中的pH值决定。在大多数生物介质中,尤其是叶绿体基质,处于平衡时,HCO_3~-浓度是CO_2浓度的十几甚至是几十倍。在这种情况下,HCO_3~-的扩散成为无机碳的主要扩散形式。碳酸酐酶(Carbonic Anhydrase EC 4.2.1.1)能够加速CO_2和HCO_3~-之间的平衡。本文对此作些     

微生物碳酸酐酶诱导CaCO_3沉淀的影响因素及生成机理

微生物碳酸酐酶能够加速CO_2的水合反应,对于研究全球碳循环具有重要的意义。选用一种产生胞外碳酸酐酶的细菌,研究了温度、pH值和Ca~(2+)浓度对细菌生长、碳酸酐酶活性的影响。结果表明,25℃碳酸酐酶的活性最高,有利于CaCO_3的沉淀;初始pH值为8.5的偏碱性环境中,CaCO_3沉淀质量最多;当Ca~(2+)浓度为50 mmol/L时,细菌的生长繁殖最好,过低的Ca~(2+)浓度会影响CaCO_3的生成,而过高的Ca~(2+)浓度则会严重影响细菌的生长,降低细菌的活性。最后研究了微生物碳酸酐酶诱导CaCO_3沉淀的机理,碳酸酐酶能够加速CO_2水化成HCO_3~-,在碱性环境中、钙源存在的情况下,与OH~-和Ca~(2+)反应生成CaCO_3沉淀。     

水生动物呼吸作用的简易实验

水生动物进行呼吸作用时,吸收水中溶解的O_2,放出CO_2,CO_2溶于水成为H_2CO_3。H_3CO_3解离成H~ 和HCO_3~-,使周围环境的酸度增加。这种酸度的变化可用溴麝香草酚蓝(BTB)指示。BTB的变色范围为pH6.0—7.6,酸性呈黄色,碱性呈蓝色,中间经过绿色(变色点为pH7.1)。色泽差异显     

非光合固碳微生物的碳源组合优化

二氧化碳(CO_2)过量排放而引起的全球变暖是目前全球面临的重大环境问题。微生物固碳是实现二氧化碳资源利用的一种重要方式。探索无需光照的高效固碳微生物对于更广泛环境条件下的微生物固碳具有重要意义。在从全球各大海域筛选富集出非光合微生物茵群的基础上,本文构建了在不同的电子供体条件下(铵和氢气)促进非光合微生物茵群生长的最佳混合碳源组合,得到如下结果:在以NH_4~+为电子供体的条件下,优化后的碳源组合为374.24 mgC/L碳酸钠(Na_2CO_3),54.76 mgC/L碳酸氢钠(NaHCO_3)和0 mgC/LCO_2时,最佳响应值TOC为3.06 mg/L。最佳响应值TOC低于以Na_2CO_3为单一碳源时,但高于以CO_2或NaHCO_3为单一碳源时;在以H_2为电子供体条件下,使用优化后的混合碳源为0.26 mg/L Na_2CO_3、0.59mg/L NaHCO_3和71.48mL/L CO_2时,非光合微生物菌群的固碳效率可达27.62 mg/L,较以CO_2为单一碳源提高35%左右。这可能意味着有H_2条件下非光合微生物菌群中的微生物可能以羟基丙酸固碳途径为主,而且多条固碳途径均能被混合菌群利用。     

不同淋洗水量下胶州湾养殖池塘土壤盐分淋洗规律

针对养殖池塘严重盐渍化现象,为确保土地资源和水资源的有效利用,通过室内土柱试验探讨不同淋洗水量下胶州湾养殖池塘土壤盐分淋洗规律,并确定最佳用水量。结果表明:随着淋洗水量的增加,土壤及其淋滤液的含盐量均以指数形式下降,为兼顾淋洗效果和节约用水,接近1:1的水土比可以达到较好的改良效果;在脱盐过程中,土壤中Ca~(2+)、Mg~(2+)、K~+、Na~+、Cl~-含量均呈下降趋势,SO_4~(2-)含量呈先上升后下降的趋势,CO_3~(2-)、HCO_3~-含量呈上升趋势;淋滤液中各盐离子浓度与土壤各盐离子变化规律类似;土壤各盐离子脱盐率大小大致表现为Cl~-Na~+K~+Ca~(2+)Mg~(2+)SO_4~(2-)HCO_3~-;随着淋洗水量的增加,土壤中离子组成由原来的Cl~-和Na~+为主先转变为以Na~+、K~+和SO_4~(2-)为主,最后转变为Na~+、HCO_3~-和K~+为主。土壤脱盐过程伴随着土壤碱化现象,因此需要对盐渍土脱盐过程中的碱化现象进行进一步研究。     

对植物矿质营养两个概念的思考

1 生理酸性盐和生理碱性盐理论植物矿质营养盐的生理酸性和生理碱性理论是1881年由A. Mayer提出的,至今已有110年的历史了。这期间矿质营养理论有了长足的进步。因此有必要在新的研究成果的基础上,更深入地了解这一理论。 1.1 根诱生的根际pH变化是怎样发生的植物根际土壤pH变化是由根系活动产生的,原因主要有三个:(1)根排泌H~+或HCO_3~-(OH~-当量);(2)根释放CO_2;(3)根的分泌物(有机酸、氨基酸)。后两种情况不是主要原因,因为在通气的土壤中,CO_2通过充气孔隙迅速扩散掉,而且HCO_3~-仅局限于土壤     

黄河三角洲柽柳植株周围土壤盐分离子的分布

为探讨柽柳的盐分富集效应及其对不同盐分离子分布的影响,以黄河三角洲盐碱地柽柳为研究对象,分析了离植株不同距离不同土层中的盐分离子组成、含量、离子比及不同离子之间的相关性。研究结果表明:各土层阳离子中Na~+含量最高,其次是Ca~(2+)和Mg~(2+),K~(+)最低,Cl~(-)在阴离子中的含量最高,SO_4~(2-)次之,HCO_3~-最低,而未检测到CO_3~(2-)。在柽柳植株周围,尤其是表层土壤中,离植株越近盐分含量越高,显示出柽柳对盐分的富集效应,其中对不同阳离子的富集程度表现为K~+Na~+Mg~(2+)Ca~(2+),而对阴离子的富集程度表现为HCO_3~-Cl~-SO_4~(2-)。冠层下凋落物中盐分的释放和树干径流可能是导致盐分在柽柳植株周围水平方向上存在差异的主要原因。土壤总可溶性盐含量随着土层的加深而升高。阳离子和阴离子向下迁移程度分别表现为Na~+Mg~(2+)Ca~(2+)K+和Cl~-SO_4~(2-)≈HCO_3~-,因而随土层加深而升高的Na~+、Ca~(2+)、Mg~(2+)和Cl~-,显示出底聚特征,而K+、SO_4~(2-)和HCO_3~-含量则随着土层的加深而降低,具有表聚特征。降水淋溶、盐分离子迁移速率的差别和各土层中不同生物量根系对盐分吸收的差异可能是造成盐分在垂直方向上含量变化的主要因素。     

夏季石灰土CO_2昼夜动态及其影响因素

土壤呼吸是土壤释放CO_2的过程,土壤CO_2动态及其控制因素的研究对于陆地生态系统碳收支核算和气候变化研究具有重要意义。本研究以喀斯特地区石灰土为对象,利用红外传感器(Vaisala GMP252)和自动装置高频次观测手段,测定了夏季土壤CO_2浓度和表观土壤呼吸速率(即土壤表面CO_2通量)的昼夜动态变化及其对集中降雨的响应特征,并分析了土壤CO_2浓度、表观土壤呼吸速率与土壤温度和湿度之间的关系。结果表明,土壤CO_2浓度的昼夜变化总体上呈现单峰变化趋势,峰值出现在正午(12:00—13:00)。此外,土壤CO_2浓度在集中降雨过程中呈"V"字型快速响应特征。土壤CO_2浓度与土壤温度呈正相关,而与土壤湿度呈负相关,石灰土偏碱性的环境使降雨时充填于土壤孔隙的水体中HCO_3~-、CO_3~(2-)及CO_2的平衡对土壤CO_2浓度变化具有重要影响。表观土壤呼吸速率的整体变化趋势与土壤温度和CO_2浓度变化一致,但前二者的变化与CO_2浓度相比略为滞后。表观土壤呼吸速率与土壤温度呈显著相关,而与土壤CO_2浓度的相关性不明显。土壤温度和湿度可以解释45%的表观土壤呼吸速率变化。因此,集中降雨影响下的石灰土表观土壤呼吸在短时间尺度上的变化主要受降雨、温湿度等环境因子影响下的土壤CO_2与空气交换过程的控制。     

两株绿藻响应CO2浓度变化的生长和生理特性的研究

以小球藻FACHB-1580和栅藻FACHB-1618为研究对象,比较了两株绿藻在0.04%CO_2、5%CO_2和20%CO_2(v/v)三种通气培养条件下的生长和生理特性的响应,试图阐述与无机碳利用相关生理参数和微藻利用CO_2能力的关系。结果表明,两株绿藻均能高效利用CO_2,在5%(v/v)条件下均表现出最大生物量积累、最大比生长速率和最大二氧化碳固定速率。小球藻FACHB-1580和栅藻FACHB-1618最大生物量分别为3.5和5.4g/L,分别是0.04%CO_2(v/v)条件的1.41和1.46倍。在高达20%CO_2(v/v)条件下,两株绿藻的生物量均显著高于空气组(P0.05)。随着CO_2浓度的增加,两株绿藻的无机碳亲和力、胞内和胞外CA活性、初始Rubisco活性,及Rubisco活化度均有下降趋势,总的Rubisco活性变化不明显。另外,小球藻FACHB-1580存在较高的胞外和胞内CA活性;而栅藻FACHB-1618胞外CA活性几乎为零,胞内CA活性显著低于小球藻FACHB-1580。由此推测,小球藻FACHB-1580能同时吸收介质中的HCO_3~-和CO_2,其胞内CA催化胞内HCO?3快速转化为CO_2,从而为Rubisco提供充足的CO_2来源;而栅藻FACHB-1618主要吸收介质中的CO_2,其胞内CA活性较低,推测其通过提高胞内CA含量,或增强Rubisco对CO_2的亲和力等促进光合固碳作用。     

固碳微生物菌株的分离鉴定及其固碳能力测定

利用微生物回收和固定CO2气体的生物固碳方法,成为解决"温室效应"这一重大环境问题的焦点,本研究目的是分离筛选固碳微生物菌株。利用无碳源无机培养基从活性污泥、沼液和设施土壤中分离筛选出以CO2为碳源的菌株24株,选取其中生长较快的8株菌进行cbbL基因、形态观察、生理生化反应测定和16S rDNA测序分析,将测序结果在BlAST数据库中比对,进行固碳菌株的分子鉴定,并对其菌体含量和RubisCO酶活性进行比较。选取RubisCO酶活性最高的菌株C2-8R,进行土壤施用试验,通过土壤RubisCO酶活性的测定,确定分离筛选的固碳菌的固碳能力。研究表明,可通过无碳源培养基进行固碳微生物菌株的筛选,筛选的固碳菌分别隶属于假单胞菌属和嗜甲基菌属,并可通过RubisCO酶活性来反映微生物的固碳能力。     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Entwicklungsgeschichte und Ultrastruktur von Pollenkitt und Exine bei nahe verwandten entomophilen und anemophilen Angiospermensippen derAlismataceae,Liliaceae, Juncaceae,Cyperaceae, Poaceae undAraceae

Some closely related members of the monocotyledonous familiesAlismataceae, Liliaceae, Juncaceae, Cyperaceae, Poaceae andAraceae with variable modes of pollination (insect- and wind-pollination) were studied in relation to the ultrastructure of pollenkitt and exine (amount, consistency and distribution of pollenkitt on the surface of pollen grains). The character syndromes of pollen cementing in entomophilous, anemophilous and intermediate (ambophilous or amphiphilous) monocotyledons are the same in principal as in dicotyledons. Comparing present with former results one can summarize: 1) The pollenkitt is always produced in the same manner by the anther tapetum in all angiosperm sub-classes. 2) The variable stickiness of entomophilous and anemophilous pollen always depends on the particular distribution and consistency of the pollenkitt, but not its amount on the pollen surface. 3) The mostly dry and powdery pollen of anemophilous plants always contains a variable amount of inactive pollenkitt in its exine cavities. 4) A step-by step change of the pollen cementing syndrome can be observed from entomophily towards anemophily. 5) From the omnipresence of pollenkitt in all wind-pollinated angiosperms studied one can conclude that the ancestors of anemophilous angiosperms probably have been zoophilous (i.e. entomophilous) throughout.

     

Identification and Characterization of the First Equine Parainfluenza Virus 5

正Dear Editor,Parainfluenza virus 5 (PIV5), known as canine parainfluenza virus in the veterinary field, is a negative-sense,nonsegmented, single-stranded RNA virus belonging to the Paramyxoviridae family (Chen 2018). The virus was first reported in primary monkey kidney cells in 1954 (Hsiung1972), then it has been frequently discovered in various