过渡金属离子(Cu2+、Cd2+)对藻红蛋白单体的漂白机制

藻胆蛋白是一组同源捕光色素蛋白,由多肽链及相连的开链四吡咯环色团构成。多肽链对色团的调控形成不同藻胆蛋白的特征吸收及荧光光谱。这些色团是藻蓝胆素(吸收带590～670 nm)、藻红胆素(吸收带530～570 nm)和藻尿胆素(吸收带490～500nm)。藻尿胆素由于在共轭体系中含有较少的双键,所以与前二者比,在较短波长有吸收。它们总是与藻红胆素伴生,在藻胆蛋白中作为敏化基团存在。

STUDY ON THE BLEACHING OF MONOMERS AND SUBUNITS OF R-PHYCOERYTHRIN BY TRANSITION METALS(Cu2+, Cd2+)

The bleaching of the monomers and the separated α and β subnits of R-phycoery-thrin from Polysiphonia urceolata by Cu²⁺, Cd²⁺, has been investigated. Upon the addition of Cu²⁺ and Cd²⁺, the visible absorption bands of the monomers at 496, 538 and 564 nm of R-phycoerythrin was bleached. The change in absorption induced by Cu²⁺ or Cd²⁺ was accompanied by a decreased fluorescence emission intensity. The bleaching capacity of Cu²⁺ is greater than that of Cd²⁺. When monomers and α subunit are bleached by Cu²⁺, there is no appearance of the characteristic absorption of chromophore complex at 648 nm. But this absorption appeares obviously in the case of β subunit. From above results, we conclude the mechanism is that the bleachng of monomers and α subunit is caused by the interaction of Cu²⁺ or Cd²⁺ with the residues of polypeptides, but β subunit is bleached by both of the interaction of Cu²⁺ or Cd²⁺ with residues of polypeptides and the coordination of Cu²⁺ or Cd²⁺ with chromophores.