根癌农杆菌电击转化条件的研究

探索了根癌农杆菌EHA105的高效转化方法.将双元载体质粒pBIN19/glgB经电击转化法导入根癌农杆菌EHA105,研究不同实验条件对转化率的影响.结果表明:在细胞浓度OD600为1.0时进行电转化,转化率最高,达到每微克DNA1.12×105CFU;当电场强度为11 kv/cm,转化率最高,达到每微克DNA1.78×105CFU;在一定的细胞浓度范围内,电击转化率与细胞浓度密切相关,转化率随着细胞浓度的上升而上升;质粒大小能影响电击转化率,转化率随着质粒的增大而下降.应用该优化的电击转化条件将双元载体质粒pBIN19/glgB成功导入根癌农杆菌EHA105,构建了植物双元表达载体.     

Magnetoelectric and converse magnetoelectric res ponses in TbxDy1-xFe2-y alloy ＆ Pb（Mg1/3Nb2/3）（1-x）TixO3 crystal laminated composites

Measured results of magnetoelectric （ME） and converse magnetoelectric （CME） effects of TbxDy1-xFe2-y/ Pb（Mg1/3Nb2/3）（1-x）TixO3/TbxDy1-xFe2-y （TD/PMNT/TD） and PMNT/TD/PMNT laminated composites are presented. ME effect was determined by measuring laminate voltage output under a Helmholtz-generated AC field biased by a DC field （0-1 kOe） （1Oe = 79.58 A/m）. The CME effect was measured by recording the voltage induced in a solenoid encompassing the ME sample while exposed to a DC bias field and PMNT layer driven by a 10 V AC source. The ME and CME responses in the two laminated structure are linear. The highest values of ME coefficients in TD/PMNT/TD and PMNT/TD/PMNT composites are 384 mV/Oe and 158 mV/Oe, respectively, while the highest values of CME coefficients in the two composites are 118 mG/V and 162 mG/V （1 G=10^-4 T）, respectively.     

脉冲电场作用下Hela细胞穿孔率研究

以宫颈癌Hela细胞为实验对象，利用自制脉冲电源和台盼蓝染色法计数，针对不同的电脉冲参数作用于Hela细胞上，研究了细胞可逆和不可逆电穿孔的场强阈值范围，重点研究了脉冲个数、脉冲宽度和电场强度对细胞不可逆穿孔率的影响，并选择了优化的参数组合。实验发现，在固定脉冲宽度50 μs和20个脉冲个数不变的情况下，Hela细胞出现可逆电穿孔（存活）的场强阈值范围分别为500～750 \begin{document}$ \mathrm{V}/\mathrm{c}\mathrm{m} $\end{document}，出现不可逆电穿孔（死亡）的场强阈值范围为750～1 000 \begin{document}$ \mathrm{V}/\mathrm{c}\mathrm{m} $\end{document}。在对电脉冲参数优化组合的实验中，Hela细胞的不可逆穿孔率随着脉冲个数、脉冲宽度和脉冲场强的增加而增加，最终趋于饱和。宜选择场强1 500 \begin{document}$ \mathrm{V}/\mathrm{c}\mathrm{m} $\end{document}、脉宽60 μs和70个脉冲的参数组合，不可逆穿孔率为93.42%。     

Novel high PSRR current reference based on subthreshold MOSFETs

This paper takes full advantages of the I-V transconductance characteristics of metal-oxide semiconductor field effect transistor （MOSFET） operating in the subthreshold region and the enhancement pre-regulator technique with the high gain negative feedback loop. The proposed reference circuit, designed with the SMIC 0.18 μm standard complementary metal-oxide semiconductor （CMOS） logic process technology, exhibits a stable current of about 1.701 μA with much low temperature coefficient （TC） of 2.5×10^-4μA/℃ in the temperature range of-40 to 150℃ at 1.5 V supply voltage, and also achieves a best PSRR over a broad frequency. The PSRR is about - 126 dB at DC frequency and remains -92 dB at the frequency higher 100 MHz. Moreover the proposed reference circuit operates stably at the supply voltage higher 1.2 V and has good process compatibility.     

Regenerating plants from cryopreserved adventitious buds of haploids in rice

A large number of adventitious buds were induced fromin vitro cultured young inflorescences of haploids of rice. Having been subcultured on solidified subculture media at 26°C for 7 days, the adventitious buds were loaded into 1.8 mL plastic cryotubes with cryoprotectant and kept on ice for 45–60 min. After cooled at a rate of 1.0°C/min down to −40°C, the samples, were kept in liquid nitrogen. The adventitious buds which have been cryopreserved for about 30 days were thawed rapidly in 38–40°C water and then plated on solidified MS medium containing 3% sucrose, 0.5 mg/L NAA and 2.0 mg/L kinetin. After plated, 23%–32% of adventitious buds resumed growth and 15%–22% regenerated plantlets. The results of this work indicated that the adventitious buds derived fromin vitro cultured young inflorescences is a critical factor for the success and subculturing adventitious buds on MS medium containing 3% sucrose and 4% sorbitol or 20% potato extract is essential to the procedure. The effective cryoprotectant is 10% DMSO (dimethyl sulfoximide)+0.5 mol/L sorbitol. Supported by the Natural Science Foundation of Hubei Province Zhang Zhihong: born in 1963, Lecturer     

电磁刺激对成骨样细胞UMR-106 DNA合成的作用

为了从细胞水平研究低频电磁场影响成骨样细胞增殖的有效物理参数 ,并为其作用机制的解释提供依据 ,论文就几种类型电磁场对成骨样细胞 UMR- 10 6DNA合成的作用进行了一系列实验 ,通过 3 H-脱氧胸苷掺入检测 DNA合成的改变 ,发现特定频率、场强 (或磁感应强度 )组合的电磁场 (脉宽 0 .2 m s,10 V/cm,12 5 Hz附近的脉冲电场 ;1V/cm,10 Hz附近的交变电场 ;0 .5 m T,5 Hz附近的交变磁场 )能促进细胞 DNA合成水平显著提高 ,表明刺激骨细胞生长的电磁场无需复杂的波形。场强对 DNA合成有重要作用 ,只有在合适的场强范围内 ,一定频率的电磁场对细胞才有刺激作用。交变磁场所诱导的电场很微弱 ,表明磁场不只是通过诱导电场发挥作用的 ,研究磁场对细胞的作用应考虑包括磁场直接作用等全部可能的机制。     

枯草芽孢杆菌突变株IA857高效转化方法的研究

【目的】研究比较枯草芽孢杆菌突变株IA857高效转化的最优方法。【方法】以质粒pHCMC04(大小为8089bp)转化突变型枯草芽孢杆菌IA857,分别用电转化法、原生质体法、电击法诱导的原生质体法、Spizizen低盐环境感受态转化法(简称S法)、低盐环境形成饥饿感受态法及其改良方案在其它突变菌株的试验方法(简称C法)进行实验,通过比较优化得出最优转化方法。【结果】采用S法转化枯草芽孢杆菌突变株IA857,质粒加入量为70ng时,转化后直接摇床培养1h转化率最高达到1.2×104 CFU/μg DNA,可以满足枯草芽孢杆菌高效转化的要求。【结论】得出了枯草芽孢杆菌突变株IA857最优转化方法并提出转化枯草芽孢杆菌的基本框架。     

Hybrid plant regeneration from interfamilial somatic hybridization between grapevine (vitia vinifera L.) and Red Thorowax (Bupleurum scorzonerifolium willd)

The protoplasts of Red Thorowax ( Bupleurum scorzonerifolium) irradiated by ultraviolet light (UV) at an intensity of 260μW/cm2 for 0, 1,2 and 3 min respectively were fused with that of grapevine ( Vitia vinifera). The regenerated 19 clones, every one derived from a single fused cell, were identified as hybrids by phenotype, isozyme, chromosome and 5S rDNA spacer region analysis. The results reveal that all of them are somatic hybrids. 11 hybrid calli including asymmetric and symmetric products regenerated somatic embryos and young leaves after 5 months of culture, of which 4 hybrid cell lines derived from asymmetric fusion regenerated plants with roots after 8-10 months of culture. Inspection of chromosome showed that regeneration of whole plant was related to the decrease of chromosome number. Identification of 5S rDNA spacer region of the plants confirmed that they were interfamilial hybrid plants.     

广西不同林龄马尾松人工林土壤碳储量动态变化

为了解不同林龄马尾松Pinus massoniana人工林土壤碳储量的动态变化,选取广西横县镇龙林场不同林龄（幼龄林、中龄林、成熟林、过熟林）的马尾松人工林为研究对象,对林地土壤有机碳含量及土壤碳储量的变化特征进行研究,并探讨其影响因素。研究表明,随着林龄递增,各土层土壤有机碳含量及土壤碳储量总体表现为增加趋势,且不同林龄的同一土层之间均差异显著。不同林龄0—60 cm土层土壤有机碳含量表现为过熟林（16.82±0.23）g/kg > 成熟林（13.47±0.14）g/kg > 中龄林（10.91±0.38）g/kg > 幼龄林（10.74±0.14）g/kg,且差异显著（P<0.05）。不同林龄0—60 cm土层土壤碳储量表现为过熟林（104.92±18.08）t/hm²>成熟林（100.52±1.18）t/hm² > 中龄林（80.25±5.34）t/hm² > 幼龄林（80.23±4.54）t/hm²,且差异显著（P<0.05）。各林龄土壤有机碳含量、土壤碳储量主要集中在0—20 cm土层,并随土层深度的增加而递减,表现为土壤碳表聚现象,表层（0—20 cm）土壤碳储量所占比例均明显高于其他土层,表明不同林龄主要影响马尾松人工林土壤表层的碳含量;不同林龄土壤有机碳含量、土壤碳储量与乔木、灌木层Shannon-Wiener指数、物种丰富度、凋落物层现存量、总孔隙度、土壤含水量、土壤pH值均无显著相关关系（P>0.05）,与根系生物量呈极显著正相关关系（P<0.01）,与土壤容重呈极显著负相关关系（P<0.01）;群落总生物量、地上部分生物量均与表层（0-20 cm）土壤有机碳含量和土壤碳储量呈极显著正相关关系（P<0.01）,与20-40,40-60 cm土层土壤有机碳含量呈显著正相关关系（P<0.05）,而与后两个土层的土壤碳储量均无显著相关。该结果为研究土壤碳储量动态变化提供科学依据,有利于实现尾松人工林多目标可持续经营。     

Transformation character of ferrite formation by a ledge mechanism under a mixed-control model

A mixed-control model was developed to study the transformation character of ferrite formation by a ledge mechanism. A numerical two-dimensional diffusion-field model was combined to describe the evolution of the diffusion field ahead of the migrating austenite/ferrite interface. The calculation results show that the bulk diffusion-controlled model leads to a deviation from experimental results under large solute supersaturation. In the mixed-control model, solute supersaturation and a parameter Z together determine the transformation character, which is quantified by the normalized concentration of carbon in austenite at the austenite/ferrite interface. By comparing with experimental data, the pre-exponential factor of interface mobility, M₀, is estimated within the range from 0.10 to 0.60 mol·m·J-1·s-1 for the alloys with 0.11wt%-0.49wt% C at 700-740℃. For a certain Fe-C alloy, the trend of the transformation character relies on the magnitude of M 0 as the transformation temperature decreases.     

Nitrogen-fixing inhibition by KCl in a blue-green algaAnabaena cylindrica

Growing in the medium containing 0.10 mol/L KCl for three days, the nitrogen-fixing activity ofAnabaena cylindrica decreased by 95%. Extent of the inhibition was enchanced with increased KCl concentrations. The biggest decrease of nitrogen-fixing activity was between 0.02–0.05 mol/L KCl. The same decline on growth was between 0.05–0.10 mol/L KCl. The longer treating-time was, the lower nitrogen-fixing activity was. A short time of KCl-treatment (for 4 h) resulted in 66.4% decrease of the activity. Under effecting of KCl for three days, the frequency of heterocyst differentiation decreased from 7.2% to 2.1%. Supported by the National Natural Science Foundation of China Yi Ping: born in 1974, Graduate student     

Authigenic sulfide minerals and their sulfur isotopes in sediments of the northern continental slope of the South China Sea and their implications for methane flux and gas hydrate formation

This is a report of the study of the authigenic sulfide minerals and their sulfur isotopes in a sediment core (NH-1) collected on the northern continental slope of the South China Sea, where other geo-physical and geochemical evidence seems to suggest gas hydrate formation in the sediments. The study has led to the findings: (1) the pyrite content in sediments was relatively high and its grain size relatively large compared with that in normal pelagic or hemipelagic sediments; (2) the shallowest depth of the acid volatile sulfide (AVS) content maximum was at 437.5 cm (>2 μmol/g), which was deeper than that of the authigenic pyrite content maximum (at 141.5-380.5 cm); (3) δ 34S of authigenic pyrite was positive (maximum: 15‰) at depth interval of 250-380 cm; (4) the positive δ 34S coincided with pyrite enrichment. Compared with the results obtained from the Black Sea sediments by Jorgen-sen and coworkers, these observations indicated that at the NH-1 site, the depth of the sulfate-methane interface (SMI) would be or once was at about 437.5-547.5 cm and the relatively shallow SMI depth suggested high upward methane fluxes. This was in good agreement with the results obtained from pore water sulfate gradients and core head-space methane concentrations in sediment cores collected in the area. All available evidence suggested that methane gas hydrate formation may exist or may have existed in the underlying sediments.     

Preparation and properties of microencapsulated genetically engineered bacteria cells for oral therapy of uremia

~~Preparation and properties of microencapsulated genetically engineered bacteria cells for oral therapy of uremia~~     

Sequence modification of merB gene and high organomercurial resistance of transgenic tobacco plants

Mercury pollution has caused severe damage to environment and great attention has been paid to its control. Phytoremediation may become one of the most efficient measures to recover the polluted soil since it is economical, highly efficient and friendly to environment. In this report, plant genetic engineering methods were employed to modify the DNA sequence of merB genes that catalyze the conversion of organomercurals into ionic mercury. The modified merBhe genes were introduced into tobacco by Agrobacterium, and the resultant transgenic plants were verified by Southern and Northern hybridization. High level of organomercurial resistance was detected on progenies of transgenic plants, some of which were resistant to PMA (phenyl mercury acetate) of 2.5 μmol/L whereas 0.1 μmol/L PMA killed the seedlings of wild-type tobacco in soiless culrure. With the increase of PMA concentration, the inhibition of the seedling growth became apparent. This result makes it possible to breed mercury-resistant tobacco for phytoremediation of mercury-polluted soil.     

Preliminary study of microscale zircon oxygen isotopes for Dabie-Sulu metamorphic rocks： Ion probe in situ analyses

151 in situ analyses of oxygen isotopes were carried out by ion micro-probe for zircons from 8 localities of HP-UHP metamorphic rocks including eclogites in the Dabie-Sulu terrane. The results show significant heterogeneity in δ^18O values, with variation in different rocks from -8.5‰ to 9.7‰ and within one sample from 2‰ to 12‰. No measurable difference in δ^18O was observed between protolith magmatic (detrital) zircons and metamorphic recrystallized zircons within analytical uncertainties from the ion micro-probe measurements. This indicates that the metamorphic zircons have inherited the oxygen isotopic compositions of protolith zircons despite the HP to UHP metamorphism. According to their protolith ages from zircon U-Pb in situ dating by the same ion micro-probe, two groups of oxygen isotope composition are recognized, with one having δ^18O values of 6‰-7‰ for old protolith of 1.9-2.5 Ga ages and the other 0‰-2‰ for young protolith of 0.7-0.8 Ga ages. The latter anomalously low δ^18O values of zircons indicate that the magma has had the obvious involvement of meteoric water when forming the young protolith of high-grade metamorphic rocks. This may be correlated with the snowball Earth event occurring in South China and the world elsewhere during the Neoproterozoic.     

Transformation of Streptococcus zooepidemicus with Genes Responsible for Polyhydroxybutyrate Synthesis

IntroductionGenetic manipulation of bacteria has become apowerful tool for elucidating fundamentalbiological mechanisms.While many techniques areavailable to introduce foreign DNA into severalbacterial species[1 ] ,some bacteria,such asStreptococcus spp.,have proven to be resistant totransformation with mostprotocols thathave beendescribed.In addition,there are large differencesin the transform ability among various strains ofStreptococcusspp.　Streptococci have been divided into six majorph…     

Atomic force microscopic observation on substructure of pollen exine inCedrus deodara andMetasequoia glyptostroboides

The substructure of pollen exine inCedrus deodara (Roxb.) Loud. andMetasequoia glyptostroboides Hu et Cheng has been examined with an atomic force microscope (AFM). The results indicate that the exine substructure units containing sporopollenin in two species are similar in shape, which are granular, but slightly different in size. InCedrus the substructure unit of pollen exine appears to be 56–99 nm long and 42–74 nm wide, while inMetasequoia it appears to be 81–118 nm long and 43–98 nm wide. It has been observed that the subunits of pollen exine inCedrus arranged tightly to form short-rod-like or spheroidal pollen exine units, several or more than ten of which formed an island-like structure. There are various spaces among these island-like structures which are interconnected to occupy the entire pollen exine. InMetasequoia, the subunits of pollen exine also arranged tightly with a distribution tendency of cluster of 3–10, however, no obvious boundary exists among these clusters. From our results, it is concluded that there is no tendency of helical arrangement for the subunits of pollen exine inCedrus andMetasequoia, and the results support Southworth’ view that subunits of pollen exine are granular shape in lattice structure.     

Surface Dissociation Properties of Short Chain Carboxyl Mercaptan Self-Assembled Monolayers by Impedance Titration

Impedance titration was used to determine the surface dissociation characteristics of short-chain carboxyl mercaptan self-assembled monolayers （SAMs）. Based on the change of the cyclic voltammetric peak current and the charge-transfer resistance, which was related to pH value of the solution, the surface pKa of mercaptoacetic acid（MA）, 3-mercaptopropionic acid（MPA） and ω-mercaptohexanic acid（MHA） self-assembled membranes, with ionic strength being 0.1 mol/L, were determined to be 5.20, 4.80, 7.40, respectively. In addition, factors such as time needed for assembling, structure of monolayers and ionic strength, which effected the surface pKa, were studied as well. Such surface pKa shifts were sufficiently explained by interactions between interfacial molecules and hydrophobicity.     

Detection of methane plumes in the water column of Losatchev hydrothermal vent field, Mid-Atlantic Ridse

During DY105-17 cruise onboard the PJV ＂Da Yang Yi Hao＂ in 2005, methane concentrations in the water column above Logachev hydrothermal vent field were measured by applying stripping/trapping-gas chromatographic （GC） and the distinct methane plumes were detected. Results show that the background methane concentration within the Logachev area is from 1.05 nmol/L to 1.68 nmol/L, significantly higher than the background level of the Atlantic abyssal plain of 0.4-0.5 nmol/L, suggesting that hydrothermal venting is a major source of dissolved methane to the ocean. The highest anomalies of methane concentrations in the water column range from 7.14 nmol/L to 113.9 nmol/L and occur just at 180-500 m above the seafloor. The distribution of methane concentration and the structural characteristics of hydrothermal plumes are strongly influenced by the supply of underlying hydrothermal fluids, the mixing process of ocean bottom currents and the microbial oxidation. Furthermore, the differences in distribution of methane plume between the station MAR-CTD3 and the other stations indicate a probable unknown hydrothermal vent site nearby. There occurs high concentration of methane along with temperature and nephelometry anomalies, which strongly confirms that the subtle measurement of methane concentration in water column is one of the effective ways to locate active sites of hydrothermal venting.