幽门螺杆菌尿素酶的提取与纯化

采用2种方法分离纯化了幽门螺杆菌尿素酶。第1种方法是以 DEAE-sepharose FF离子交换剂和Superdex 200凝胶为分离介质,用 NaCl盐浓度梯度洗脱法从幽门螺杆菌超声上清液中提取纯化尿素酶抗原,所得到的纯化尿素酶经SDS-PAGE电泳分析,表明它具有很高的纯度,只含有分子质量为64 000 u和31 000 u两种蛋白成分,分别对应于幽门螺杆菌尿素酶的A、B两种亚基。第2种方法是以 DEAE-sepharose FF离子交换剂为分离介质,采用先去掉部分杂蛋白的方法纯化尿素酶,其中的去杂步骤操作简单、快捷且处理样品量大,大大减轻了后面纯化步骤的难度,适合于尿素酶的大量制备。纯化的尿素酶作为抗原采用ELISA间接法检测抗HP蛋黄免疫球蛋白(IgY),实验表明,其仍具有良好的抗原性,是HP主要抗原物质。应用纯化尿素酶抗原或纯化尿素酶抗原与超声粉碎抗原的混合抗原刺激蛋鸡应该能够产生抗HP效价更高的蛋黄免疫球蛋白,可以将其应用于保健或各种与HP相关的胃病的抗菌免疫治疗。

Effect of salt gradients on DNA translocation through solid-state nanopores

Aiming at the issues of controlling the translocation speed of DNA through a solid-state nanopore and enlarging the signal-to-noise ratio of ionic current modulation, which are challenges for the application of nanopore technology in DNA detection, salt concentration gradients are applied across the nanopore to investigate their influence on the DNA translocation time and signal-to-noise ratio. Experimental data demonstrates that, in symmetric concentration conditions, both the current blockade and dwell time for A-DNA translocation through a solid-state nanopore increase along with potassium chloride concentration. When the concentration in the trans chamber is decreased from 1 to 0.1 mol/L, keeping the concentration of the cis chamber at 1 mol/L, the normalized current blockade is found to be increased by one order. The increased dwell time and enhanced signal-to-noise ratio are achieved with salt gradients across the nanopore, which can improve the sensitivity when detecting DNA samples.

Effect of nitrate supply on the facilitation between two salt-marsh plants (Suaeda salsa and Scirpus planiculmis)

Aims In estuarine salt-marshes,nitrate supply and soil salinity,which are known as two main environmental drivers,simultaneously affect the interspecific interactions between plant species.However,to date,their interactive effects on interspecific interactions have not been closely examined for salt-marsh plant species.Methods Juvenile plants of Suaeda salsa L.(Chenopodiaceae)and Scirpus planiculmis Fr.(Cyperaceae)were grown in rinsed river sand to conduct a greenhouse experiment with three treatment categories:interspecific interaction(mixed culture or monoculture),three salinity levels(1,50 and 100 mmol L^(-1))and three nitrate levels(0.5,5 and 10 mmol L^(-1)).First,height and biomass of all plants were measured.Then,the growth data,relative interaction index and competitive important index of the two species were analyzed.Important Findings The interspecific interactions between S.salsa and S.planiculmis were facilitation across the salinity gradients.The promotion of S.salsa growth with high nitrate supply did not enhance the facilitative effect of the species,especially at low salinity.However,high nitrate supply significantly shifted the interspecific interactions of S.planiculmis from facilitation to competition at high salinity.Our results suggest that excessive nitrate application changes the prediction of the stress-gradient hypothesis along a salinity gradient,leading to collapse of the two species coexistence in the salt-marshes.These findings make a contribution to the understanding of how S.salsa and S.planiculmis,as well as salt-marsh communities,respond to the human modification of estuarine nutritional levels.

Transformation and source of nutrients in the Changjiang Estuary

The concentrations of phosphate （PO43 ）, ammonium, nitrite, nitrate, silicate, dissolved organic nitrogen （DON）, dissolved or- ganic phosphorus （DOP）, particulate phosphorus （PP） and particulate nitrogen （PN） along the salinity gradient were measured in the Changjiang Estuary in April 2007. The behavior of nutrient species along the continuum from the freshwater to the coastal zone is discussed. In the mixing zone between the riverine and marine waters, nitrate and phosphate behave non-conservatively, while silicate behaves conservatively. Nutrient import was quantified from the fiver load. Nutrient export to the sea was quantified from fiver discharge and from the salinity-nutrient gradient in the outer estuary. Using these data, a nitrogen and phosphorus budget was made. The internal estuarine fluxes played an important role in the nutrient estuarine fluxes, which accounted for approximately 41% of the nitrogen flux and 45% of the phosphorus flux. The mixing experiments in the laboratory generally reproduced well the inorganic process affecting nutrient dynamics in the Changjiang Estuary, indi- cating that the primary P and N transformation processes were phosphate and nitrate desorption along the salinity gradient.