La3＋或Eu3＋与微过氧化物酶-8相互作用强弱的研究

研究了La3＋或Eu3＋与微过氧化酶-8(MP-8)相互作用并比较了它们与MP-8相互作用的强弱. 紫外-可见(UV-Vis)吸收光谱和电化学的结果表明, 不论在不含NaCl或含NaCl的溶液中,一个La3＋或Eu3＋优先与MP-8分子中血红素上两个丙酸基中的羧基氧发生强的键合作用,而过量的La3＋或Eu3＋与肽链上的羰基氧发生弱的相互作用.实验结果还清楚地证明Eu3＋与MP-8的相互作用要强于La3＋与MP-8的相互作用.

Study on the Interaction Strength of La3+ or Eu3+ with Microperoxidase-8

The interaction of La3＋ or Eu3＋ with MP-8 was studied and the interaction strength of La3＋ or Eu3＋ with MP-8 was compared. Comparing with the UV-Vis absorption spectrum of the MP-8 solution without La3＋ or Eu3＋,the position of the Soret band for the MP-8 solution with La3＋ or Eu3＋ shifts to the red direction and the absorbance decreases. The extents of the red shift of the band position and the decrease in the absorbance for Eu3＋ in the solutions without or with NaCl are larger than that for La3＋. In 0.10 mol?L－1 NaCl solution, La3＋ or Eu3＋ could completely coordinate with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule when the molar ratio of La3＋ or Eu3＋ and MP-8 is 10 and 5, respectively. In addition, the cyclic voltammetric results showed that the redox peak area of Eu3＋ decreased 20％ after adding MP-8 into the solution. These results clearly illustrated that one La3＋ or Eu3＋ ion would coordinate strongly with carboxylate oxygen of two propionic acid groups of the heme group in an MP-8 molecule and the excessive La3＋ or Eu3＋ ions weakly interact with the carboxylate oxygen in the peptide chain. The interaction between Eu3＋ and MP-8 is stronger than that between La3＋ and MP-8.