| 摘要: |
| 于1996年8-12月，从钝顶螺旋藻中分离纯化C-藻蓝蛋白，并用荧光光谱法对C-藻蓝蛋白分子内不同基团间的能量传递进行研究。结果表明，C-藻蓝蛋白分子内芳香族氨基酸残基能将能量传至与脱辅基蛋白共价结合的色基，从而使色基产生相应的荧光；C-藻蓝蛋白分子240-245nm的荧光激发峰产生于二硫键，它也能将吸收的能量传至色基；同时还发现，溶液状态下的C-藻蓝蛋白分子内，色氨酸残基可能位于分子内部的疏水区，而二硫键则位于分子表面的非荷电区域。这些均可作为开展C-藻蓝蛋白分子天然构象研究的结构表征。 |
| 关键词: 钝顶螺旋藻 C-藻蓝蛋白 二硫键 芳香族氨基酸残基 荧光光谱 |
| DOI： |
| 分类号: |
| 基金项目:国家自然科学基金资助项目，39700010号 |
附件 |
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| STUDIES ON ENERGY TRANSFER BETWEEN DIFFERENT GROUPS IN SPIRUNINA PLATENSIS C—PHYCOCYANIN |
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WANG Guang-ce,ZENG Cheng-kui (C. K. Tseng)
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Experimental Marine Biological Laboratory, The Chinese Academy of Sciences, Qingdao, 266071
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| Abstract: |
| From August to December of 1996, C-phycocyanin was purified from spirulina platensis, and energy transfer between different groups in C-phycocyanin was studied in terms of its fluorescence spectra. The purification of the C-phycocyanin was based upon the use of a hydroxylapatite chromatography and the purity was 5 (A620/A280). The C-phycocyanin showed two fluorescence peaks at 355 nm and 650 nm at the excitation wavelength of 280 nm, which is attributed to the absorption of aromatic amino acid residues in apoprotein of the C-phycocyanin; this is also the case for the C-phycocyanin when excited at 240 nm. If the C-phycocyanin was denatured, then the fluorescence peak at 650nm decreased greatly, whilst the fluorescence peak at 355 nm was shifted to 380 nm and the relative fluorescence intensity increased. However, if the C-phycocyanin was denatured or DTT was added to the C-phycocyanin solution, then all fluorescence peaks disappeared at the excitation wavelength of 240 nm. The results show that the energy which is absorbed by the aromatic amino acid residues can be transferred from the aromatic amino acid residues to the chromophore which is conjugated to apoprotein in C-phycocyanin in solution to make it produce fluorescence; it is found that the fluorescence excitation peak at 240 - 245 nm results from disulfide bonds in C-phycocyanin and the energy can also be transferred from disulfide bonds to chromophore of C-phycocyanin. With the help of some quenchers, the location of the tryptophan residues of the C-phycocyanin was found in the hydrophobic region of the inner molecules and that of disulfide bonds in the nonelectrostatic part of the C-phycocyarnin molecule surface. The mechanism of energy transfer between the aromatic amino acid residues in apoprotein of C-phycocyanin and the chromophore of C-phycocyanin may be associated with the Forster Dipole-dipole resonance because of the overlap of fluorescence emission peak of tryptophan residues at 355 nm with the absorption peak of the chromophores of C-phycocyanin, which are called phycocyanobilin, at 360 nm. On the other hand, the mechanism of energy transfer between the disulfide bonds of the apoprotein of C-phycocyanin and the chromophore of C-phycocyanin may be related to excitation coupling because the disulfide bonds in apoprotein do not produce fluorescence. Thus, the energy transfer between different groups can serve as structure characters in phycobiliproteins. |
| Key words: Spirulina platensis, C-phycocyanin, Disulfide bond, Aromatic amino acid residues, Fluorescence spectra |
