| 摘要: |
| 于1992年9月-1995年1月将极大、钝顶、盐泽等三种螺旋藻在加4-100 mg/L硒浓度的培养基内培养，研究藻细胞及其蛋白质、多糖和脂类结合硒的量，探讨硒的结合机理。结果表明，极大螺旋藻累积的硒随外加硒的浓度而增加，但累积系数接近平均值2.184；在同样的硒浓度（8 mg/L）条件下，盐泽螺旋藻对硒的累积远大于极大和钝顶两种螺旋藻的，高达696.968×10-6；极大螺旋藻中蛋白质和脂类结合的硒分别占藻细胞含硒量的14.63％和16.05％，两者均高于其它两种藻中相对应的量；三种藻细胞多糖结合硒的能力均很弱，但胞外多糖结合硒的能力较强。根据实验结果推测，螺旋藻累积硒的机理一方面是大分子化合物的吸附作用，另一方面是通过生化过程使硒与蛋白质和脂类结合形成大分子化合物。 |
| 关键词: 螺旋藻 硒 累积 蛋白质 多糖 脂类 |
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| STUDY ON THE ACCUMULATION OF SELENIUM AND ITS BINDING TO TI-IE PROTEINS, POLYSACCHARIDES AND LIPIDS FROM SPIRULINA MAXIMA, SPLATENSIS AND S. SUBSALSA |
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Zhou Zhigang, Li Pengfu, Liu Zhili, Liu Xuexian
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Department of Biological Science and Technology Nanjing University,Nanjing 210093
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| Abstract: |
| The present experiments were carried out from September l992 to January 1995, and the algal species were provided by Laboratory of Algal Research, Department of Biological Science and Technology, Nanjing University. The culture of a blue-green alga Spirulina maxima in the Zarrouk's media with various contents of sodium selenite, i. e. 4, 8, 12, 16, 20, 40, 60, 80 and 100 mg/L selenium, shows that selenium accumulated by this alga increases with added selenite, but the accumulation ratio is close to a mean value of 2.184 (Tab. l). According to this observation, the culture condition of 8 mg/L selenium was chosen to compare the accumulation of selenium in S. maxima, S. platensis and S. subsalsa, to study the mechanisms of this accumulation. In the medium containing 8 mg/L selenium, S. subsalsa accumulated 696.968 μg selenium per gram dry weight (Tab. 2), which was 72 and 5.7 times as much as S. maxima and S. platensis, respectively. After preliminary purification, the crude isolated proteins of these algae were separated on Sephadex G-100 column chromatography into Parts A, B and C (Fig.1), and the lipids on silica gel column into polar and neutral lipids. Selenium bound to proteins and lipids in S. maxima accounted for 14.63% and 16.05% (Tab. 3), respectively, of the total selenium accumulated, much higher than those of S. plalensis and S. subsalsa, although the absolute contents of selenium accumulated by S. maximal were lower than S. platensis and S. subsalsa (Tab.2). Half of selenium bound to proteins was in Part A (Tab. 3), which was almost chlorophyll-bound proteins (Fig.2), while that bound to polar lipid accounted for two thirds of its total content in lipids (Tab. 3). The extracellular polysaccharides were separated into fractions I and II on DEAE-Sephadex A-25 column chromatography, while the endocellular ones also into fractions I and II with the exception of these in S. platensis consisting of only one fraction. The fact that selenium bound to the extracellular polysaccharides was much higher than that to the endocellular ones (Fig.3) indicates that the extracellular polysaccharides are very easy to form coordination compounds with selenium, while the endocellular polysaccharides could not easily do this way. From the above results, the mechanisms of selenium accumulation by these algae are deduced to be physical absorption by macromolecules, e.g. the peptidoglycan of the algal cell walls, and biochemical formation of seleno-macromolecullar compounds with the proteins and lipids, such as the replacement of sulfur by selenium in peptides. S. platensis and S. subsalsa accumulated selenium mainly by the former mechanism, and S. maxima accumulated it dominantly by the latter one. |
| Key words: Spirulina, Selenium, Accumulation, Proteins, Polysaccharides, Lipids |
