Sulfate reduction and S-oxidation in a moorland pool sediment

In an oligotrophic moorland pool in The Netherlands, S cycling near the sediment/water boundary was investigated by measuring (1) SO₄ ^2– reduction rates in the sediment, (2) depletion of SO₄ ^2– in the overlying water column and (3) release of³⁵S from the sediment into the water column. Two locations differing in sediment type (highly organic and sandy) were compared, with respect to reduction rates and depletion of SO₄ ^2– in the overlying water.Sulfate reduction rates in sediments of an oligotrophic moorland pool were estimated by diagenetic modelling and whole core³⁵SO₄ ^2– injection. Rates of SO₄ ^2– consumption in the overlying water were estimated by changes in SO₄ ^2– concentration over time in in situ enclosures. Reduction rates ranged from 0.27–11.2 mmol m^–2 d^–1. Rates of SO₄ ^2– uptake from the enclosed water column varied from –0.5, –0.3 mmol m^–2 d^–1 (November) to 0.43–1.81 mmol m^–2 d^–1 (July, August and April). Maximum rates of oxidation to SO₄ ^2– in July 1990 estimated by combination of SO₄ ^2– reduction rates and rates of in situ SO₄ ^2– uptake in the enclosed water column were 10.3 and 10.5 mmol m^–2 d^–1 at an organic rich and at a sandy site respectively.Experiments with³⁵S^2– and³⁵SO₄ ^2– tracer suggested (1) a rapid formation of organically bound S from dissimilatory reduced SO₄ ^2– and (2) the presence of mainly non SO₄ ^2–-S derived from reduced S transported from the sediment into the overlying water. A³⁵S^2– tracer experiment showed that about 7% of³⁵S^2– injected at 1 cm depth in a sediment core was recovered in the overlying water column.Sulfate reduction rates in sediments with higher volumetric mass fraction of organic matter did not significantly differ from those in sediments with a lower mass fraction of organic matter.Corresponding author     

ConA激活小鼠胸腺T淋巴细胞增殖过程中c-myc与核骨架蛋白的结合

采用DNA-蛋白质体外吸附的方法研究伴刀豆球蛋白激活小鼠胸腺T淋巴细胞增殖过程中c-myc与核骨架蛋白的结合.实验结果显示,c-myc与核骨架蛋白的结合具有特异性,在淋巴细胞激活过程中c-myc与P₃₄/P₃₆核骨架蛋白及核纤层蛋白结合,并发生动态变化.     

Energy Crop and Biotechnology for Biofuel Production

Selection of energy crops is the first priority for large-scale biofuel production in China. As a major topic, it was extensively discussed in the Second International Symposium on Bioen-     

重组人MASP2蛋白在大肠杆菌中的表达和纯化

目的:获得酶原形式的重组人甘露聚糖结合凝集素相关丝氨酸蛋白酶2(MASP2)。方法:在大肠杆菌中诱导表达重组人MASP2全长蛋白,包涵体裂解后,经复性、透析、浓缩、考马斯亮蓝染色、SDS-PAGE及Western印迹,鉴定纯化结果及酶活性。结果:复性后的MASP2蛋白经考马斯亮蓝染色未见杂带。自激活实验表明,当MASP2浓度在1μmool/L以下时,无论在4℃还是37℃,都能较稳定地保持酶原形式;蛋白浓度为3.5μmool/L时只能在4℃保持稳定,37℃发生自激活;蛋白浓度达到12μmool/L后,在4℃时已不能稳定存在。结论:获得了较纯的重组人MASP2蛋白,且具有自激活活性。     

不同季节和冬眠时相中达乌尔黄鼠视前区温敏神经元特性和下丘脑内NA代谢的变化

比较了不同季节和冬眠时相中达乌尔黄鼠 (Citelleusdauricus)下丘脑内去甲肾上腺素 (noradrenaline ,NA)代谢和视前区 (POA)脑片中各类温敏神经元的比例、温度敏感性、放电活动的临界温度及下限温度 .结果表明 :与夏季动物相比 ,( 1)冬眠各时相中POA温敏神经元的比例和温敏性产生了与冬眠体温调节特性相关的适应性改变 ;( 2 )冬季和冬眠中POA神经元放电的下限温度和温敏神经元活动的临界温度均显著下移 ;( 3 )冬眠中POA神经元对NA反应的敏感性增高 ,冷敏神经元对NA的反应从夏季的抑制型转变为冬眠时的兴奋型 ;( 4)入眠和深冬眠时下丘脑内NA的含量和代谢水平下降 ,出眠时代谢水平升高 .这些变化可能解释动物入眠时主动降低体温和出眠时从深低体温中快速地升温的温度调节机理 .     

荷木树干CO_2释放通量与木质部液流和CO_2浓度的关系

采用红外气体分析仪,于2008年10月17-19日连续3个昼夜原位监测了荷木的树干CO_2释放通量、树干温度、木质部液流密度和CO_2浓度.结果表明:树干CO_2释放通量(EA)日变化呈S形曲线,不同径级间差异显著.EA与树干温度呈显著幂函数关系(0.24

Abstract：

By using a Li-820 infra-red CO_2 gas analyzer, an in situ measurement of Schima super-ba stem CO_2 efflux was conducted for three consecutive days from 17 to 19 October 2008. In the meantime, the stem temperature, xylem sap efflux density, and xylem CO_2 concentration were measured. The stem CO_2 efflux had a diurnal variation of "S" pattern, and differed significantly with stem diameter. There was a significant exponential relationship between stem CO_2 efflux and stem temperature (0. 24 < R~2 < 0. 78). The temperature coefficient (b) and regression coeffi-cient (R~2) were higher at nighttime than at daytime, and the Q_(10) value ranged from 2. 01 to 2. 79. The stem CO_2 efflux correlated significantly with the xylem CO_2 concentration, and the best regression curve was cubic (R~2= 0. 48). Excluding the effects of stem temperature, the stem CO_2 efflux showed a significant negative correlation with xylem sap flux density (r =-0.462). Therefore, only using simple temperature function to estimate stem CO_2 efflux would yield a significant error, and xylem sap flux should be taken into consideration in the stem CO_2 emux estimation.     

铁皮石斛的离体开花

铁皮石斛(Dendrobium candidum),为一种野生兰科植物,在栽培条件下,从种子萌发到开花通常需要3～4a.研究了多种植物激素和多胺对该种石斛组织培养中花芽形成的影响,结果表明在培养基中加入合适浓度的亚精胺(spermidine)或BA(6-苄基腺嘌呤),或同时加入NAA(萘乙酸)和BA均可诱导原球茎或由之形成的无根小苗在3～6个月开花,频率在31.6%～45.8%.当将原球茎在加有ABA(脱落酸)的培养基上预培养后再移到加有BA的培养基上,花芽形成的频率可提高到平均达82.8%(个别实验中可达100%),这种诱导提早开花的现象也与实验材料的发育阶段(原球茎、无根小苗、已生根的小苗)有关,通常发生在根的形成受到完全或部分抑制的情况中.     

Tyrosine phosphorylation of Munc18‐1 inhibits synaptic transmission by preventing SNARE assembly

Tyrosine kinases are important regulators of synaptic strength. Here, we describe a key component of the synaptic vesicle release machinery, Munc18‐1, as a phosphorylation target for neuronal Src family kinases (SFKs). Phosphomimetic Y473D mutation of a SFK phosphorylation site previously identified by brain phospho‐proteomics abolished the stimulatory effect of Munc18‐1 on SNARE complex formation (“SNARE‐templating”) and membrane fusion in vitro. Furthermore, priming but not docking of synaptic vesicles was disrupted in hippocampal munc18‐1‐null neurons expressing Munc18‐1_Y473D. Synaptic transmission was temporarily restored by high‐frequency stimulation, as well as by a Munc18‐1 mutation that results in helix 12 extension, a critical conformational step in vesicle priming. On the other hand, expression of non‐phosphorylatable Munc18‐1 supported normal synaptic transmission. We propose that SFK‐dependent Munc18‐1 phosphorylation may constitute a potent, previously unknown mechanism to shut down synaptic transmission, via direct occlusion of a Synaptobrevin/VAMP2 binding groove and subsequent hindrance of conformational changes in domain 3a responsible for vesicle priming. This would strongly interfere with the essential post‐docking SNARE‐templating role of Munc18‐1, resulting in a largely abolished pool of releasable synaptic vesicles.     

胸内正压对正常人左室功能影响及其力学原理

目的：探讨胸内正压对正常人左室射血及充盈的影响及其力学原理。方法：超声心动图观测30例正常人初始时与标准乏氏动作张力期10s时左室舒张末容积（LVEDV）、左室收缩末容积（LVESV）、每搏量（SV）、射血分值（EF）、流入道血流速度（E峰、A峰）、E／A值、二尖瓣环舒张早期运动速度（e）及舒张早期充盈压（E/e）的变化。结果：与初始时比较,标准乏氏动作张力期LVEDV、LVESV及SV减低而心率（陬）增快（P均〈0．001）,EF值增加,但无统计学意义（P〉0．05）;E峰与E／A值减低（P均〈O．05）;e没有变化（P〉0．05）．E／e值减低（P〈O．05）。结论：胸内正压对左室游离壁的力学作用促进了左室收缩运动而阻碍了左室舒张运动,会引起EF值增加,E峰及E／A值减低;2,胸内正压降低了肺静脉系统与心脏的跨壁压力,增加了血流阻力也是导致肺静脉系统与左室血液回流减少．E峰减低．E／e值减低的一个原因。     

Identification of an alpha3-fucosyltransferase and a novel alpha2- fucosyltransferase activity in cercariae of the schistosome Trichobilharzia ocellata: biosynthesis of the Fucalpha1-->2Fucalpha1-- >3[Gal(NAc)beta1-->4]GlcNAc sequence

Fucose is a major constituent of the protein- and lipid-linked glycans of the various life-cycle stages of schistosomes. These fucosylated glycans are highly antigenic and seem to play a role in the pathology of schistosomiasis. In this article we describe the identification and characterization of two fucosyltransferases (FucTs) in cercariae of the avian schistosome Trichobilharzia ocellata, a GDP-Fuc:[Galbeta1-- >4]GlcNAcbeta-R alpha1-->3-FucT and a novel GDP-Fuc:Fucalpha-R alpha1-- >2-FucT. Triton X-100 extracts of cercariae were assayed for FucT activity using a variety of acceptor substrates. Type 1 chain (Galbeta1- ->3GlcNAc) based compounds were poor acceptors, whereas those based on a type 2 chain (Galbeta1-->4GlcNAc), whether alpha2'-fucosylated, alpha3'-sialylated, or unsubstituted, and whether present as oligosaccharide or contained in a glycopeptide or glycoprotein, all served as acceptor substrates. In this respect the schistosomal alpha3- FucT resembles human FucT V and VI rather than other known FucTs. N- ethylmaleimide, an inhibitor of several human FucTs, had no effect on the activity of the schistosomal alpha3-FucT, whereas GDP-beta-S was strongly inhibitory. Large scale incubations were carried out with Galbeta1-->4GlcNAc, GalNAcbeta1-->4GlcNAcbeta-O -(CH2)8COOCH3 and Fucalpha1-->3GlcNAcbeta1-->2Man as acceptor substrates and the products of the incubations were isolated using a sequence of chromatographic techniques. By methylation analysis and 2D-TOCSY and ROESY1H-NMR spectroscopy the products formed were shown to be Galbeta1-- >4[Fucalpha1-->2Fucalpha1-->3]GlcNAc, GalNAcbeta1-->4[Fucalpha1-- >2Fucalpha1-->3]GlcNAcbe ta-O-(CH2)8COOCH3, and Fucalpha1-->2Fucalpha1-- >3GlcNAcbeta1-->2Man, respectively. It is concluded that the alpha2- FucT and alpha3-FucT are involved in the biosynthesis of the (oligomeric) Lewisx sequences and the Fucalpha1-->2Fucalpha1-->3GlcNAc structural element that have been described on schistosomal glycoconjugates.