EFFECTS OF VARIATION IN TEMPERATURE. I. ON THE BIOCHEMICAL COMPOSITION OF EIGHT SPECIES OF MARINE PHYTOPLANKTON1

The influence of temperature on the biochemical composition of eight species of marine phytoplankton was investigated. Thalassiosira pseudonana Hasle and Heim-dal, Phaeodactylum tricornutum Bohlin and, Pavlova lutheri Droop (three of eight species studied) had minimum values of carbon and nitrogen quotas at intermediate temperatures resulting in a broad U-shaped response in quotas over the temperature range of 10 to 25°C. Protein per cell also had minimum values at intermediate temperatures for six species. For T. pseudonana, P. tricornutum, and P. lutheri, patterns of variation in carbon, nitrogen, and protein quotas as a function of temperature were similar. Over all species, lipid and carbohydrate per cell showed no consistent trends with temperature. Only chlorophyll a quotas and the carbon: chlorophyll a ratios (θ) showed consistent trends across all species. Chlorophyll a quotas were always lower at 10°C than at 25°C. Carbon: chlorophyll a ratios (θ) were always higher at 10°C than at 25°C. We suggest that although θ consistently increases at lower temperatures, the relationship between temperature and θ ranges from linear to exponential and is species specific. Accordingly, the interspecific variance in θ that results from species showing a range of possible responses to temperature increases as temperature declines and reaches a maximum at low temperatures. High photon flux densities appear to increase the potential interspecific variance in the carbon: chlorophyll a ratio and therefore exacerbate these trends.     

EFFECTS OF HELPER PROTEINS ENCODED BY p19 AND orf1-orf2 GENES ON Cyt1Aa PROTEIN EXPRESSION IN ACRYSTALLIFEROUS STRAIN OF BACILLUS THURINGIENSIS

A series of plasmids were constructed to examine the effects of p19 and orf1‐orf2 genes from Bacillus thuringiensis on Cyt1Aa synthesis and inclusion formation. The plasmids expressed the cyt1Aa gene along with either p19 or orf1‐orf2, or each of them coordinatively with p20 in the acrystalliferous strain of B. thuringiensis subsp. israelensis 4Q7. No effect on the expression of Cyt1Aa protein was found when P19 or Orf1‐Orf2 co‐expressed with Cyt1Aa. However, when including p20 gene, the constructs with p19 or orf1‐orf2 gene produced lower yield of Cyt1Aa proteins than without p19 or orf1‐orf2 gene. Electron microscopy observation and bioassay showed that P19 and Orf1‐Orf2 have no influence on the crystal size and toxicity of Cyt1Aa protein. It is presumed that P19 and Orf1‐Orf2 might have negative effects on Cyt1Aa synthesis in B. thuringiensis.     

Purification, biochemistry and molecular cloning of an insect glycosylasparaginase from Spodoptera frugiperda

Glycosylasparaginase (EC 3.5.1.26 [EC] ) from Sf9 cells (Spodopterafrugiperda) was purified to homogeneity with a specific activityof 2.1 unit/mg. The enzyme is composed of two non-identical     

Mutational studies of conserved residues in the dimer interface of nerve growth factor.

An understanding of the structure-function relationship of nerve growth factor (NGF) requires precise knowledge of all the residues and regions that participate in NGF receptor binding, receptor activation, and biological activity. Seven recombinant human NGF mutants having alanine substituted for residues located either in the NGF dimer interface or beta-strand region were studied to determine the role of each amino acid residue in NGF biological activity. F86A, T91A, R100A, and R103A remained nearly full active with 61, 120, 91, and 73% of wild-type activity, respectively, in the PC12 cell bioassay. Hydrophobic core and dimer interface residues Y52, F53, and F54 were studied in more detail. Y52A and F54A were expressed in very low levels, suggesting that these two residues may be important for protein stability. Y52A retained full biological activity (91%). F53A had a 20- and 70-fold reduction in biological activity and TrkA phosphorylation, respectively, with only a 5- to 10-fold effect on TrkA binding and no effect on low-affinity receptor binding. F54A had significantly decreased TrkA phosphorylation and biological activity (40-fold). The results suggest that F53 and F54 may play a structural role in TrkA receptor activation subsequent to binding.     

双水相电泳分离蛋白质的研究

近几年来,随着生物技术的迅速发展,制备型电泳技术的研究得到了重视。然而由于技术上的原因,大规模的制备型电泳技术的研究还未能取得突破。阻碍电泳放大的一个主要问题是由于电加热作用而导致的热对流对电泳分离的破坏。为解决这一问题,人们提出了许多方法。例如,在太空的微重力环境下进行电泳,应力稳定自由流动电泳,循环等电聚焦和区带电泳,色谱电泳和等电膜等电聚焦等。这些方法在电泳放大上都取得了一定的进展,但各有其局限性。最近,Clark提出利用双水相的液液界面阻止热对流的设想,为开发大规模的制备型电泳技术开辟了一条新途径、Raghava Rao等在两种双水相体系上施加电场后成倍地缩短了分相时间。Levine和Bier采用U型管电泳装置研究了双水相体系中血红蛋白的电泳迁移率,观测到界面有阻滞作用。Clark在柱型电泳装置中进行了一组双水相萃取肌红蛋白的简单实验。在10mA的恒电流下电泳40min之后,肌红蛋白的分配系数为7.5,而当电场反向后,分配系数变为0.04,界面阻力并不显著,两者结论并不一致。     

固定化细胞分布对动力学影响的模型化研究

通过对固定化Gluconobacter oxydans和Bacillus cereus的活细胞系统的研究,提出了固定化细胞不均匀分布模型,将此类分布与均匀分布(最劣分布模型)进行比较,分析了它们对固定化细胞内部的基质浓度分布、有效速率因子和选择率的影响,指出不均匀分布和均匀分布对于该固定化活细胞系统的动力学行为无显著影响,这一模型分析结果在实验中得以验证。通过无因次化分析,建立了适用于固定化生物催化剂动力学研究的模型方法。     

DISCOVERY OF VERTEBRATE FOSSILS AND PALEOLITHIC ARTIFACTS IN DANJIANG SUBMERGING AREA AND ITS IMPLICATIONS

IntheareatobefloodedinthesecondengineeringstagefortheDanjiangreservoir,wediscovered16vertebratefossillocalitiesand52Paleolithicsitesin1994,andcollected603artifactsandmanyfossils.Ofthel6new1yfoundvertebratefossillocalities,threearereptilesitesrepresentedbydinosaureggsandlimbbones,andl3producemamma1s,including4Pale0gene,2Ne0geneand7Quaternarysites'ThemammalianlocalitiesareofPale0cene,Eocene,EarlyMiocene,andPli0ceneorEarlyPleistocene,MiddleandIntePleistocene,respectively.Theyfillinsomestrat…     

Nature of Enhanced Severity of Anthurium Root Rot by Diuron Treatment for Weed Control

Diuron treatment for weed control greatly increased anthurium root rot caused by Pythium splendens, P. spinosum, P. vexans and Calonectria crotalariac. Diuron in agar medium was inhibitory to the growth of mycelium, formation and germination of sporangia of P. splendens. Sporangia of P. splendens produced in diuron-amended medium did not differ in pathogenecity to anthurium roots from those produced in diuron-free medium. When diuron was applied to kill weeds in the planting medium, the population of P. splendens in it was not decreased during the test. Diuron was inhibitory to a number of micro-organisms in the platiting medium. Exudation of anthursum roots was not increased by diuron treatment. Increase in severity of anthurium root rot by diuron treatment was similar whether the experiments were performed in the presence or absence of planting medium, suggesting that the enhancing effect of diuron on root rot is mainly due to an increase in susceptibility of the host plants.     

小麦返白系与不同基因型小麦品种杂交后代IPO表达的研究

以小麦返白系和对照矮变１号以及返白系与各不同生态类型的冬性、半冬性、春性小麦的杂交、回交Ｆ１、Ｆ２代为材料,研究这些不同基因型品种在返白期间过氧化物酶同工酶（ＩＰＯ）基因表达模式的动态变化特点。结果表明,在返白期间以返白系为母本的各杂交、回交品种的白化苗中,ＩＰＯ的个别酶分子表现了可逆的基因阻遏和去阻遏的表达现象。这种表达特点在正、反杂交后Ｆ１代中表现一致,从遗传模式上分别属于质－核互作型的分子遗