微过氧化物酶-11的聚集状态对其与Yb^3＋相互作用的影响

Effect of Aggregation Extent of Microperoxidase-11 on Its Interaction with Yb^(3+)

研究了微过氧化物酶-11(MP-11)的聚集状态对其与Yb3+相互作用的影响。紫外-可见(UV-Vis)吸收光谱研究结果表明,在纯水溶液中,由于Yb3+与MP-11分子中血红素卟啉环上的2个丙酸基团的羧基氧发生强的键合作用,使血红素卟啉环的非平面性增加,π-π跃迁所需要的能量减少,但电子跃迁几率降低。因此,MP-11吸收光谱中的Soret带红移10nm,吸光度下降35%。在NaCl溶液中,虽然NaCl能增加MP-11的聚集程度,但大量Na+的存在,大大降低了Yb3+与MP-11的相互作用。加入Yb3+后,MP-11吸收光谱中的Soret带的峰位基本不变,吸光度仅下降5%。甲醇能降低MP-11分子的聚集程度,但由于MP-11分子之间主要由配位作用以无规方式聚集,MP-11聚集程度的降低对MP-11分子中血红素的结构的影响较小。因此,聚集程度的降低对Yb3+与MP-11相互作用的影响较小。

The effect of the aggregation state of microperoxidase-11 （ MP-11 ） on its interaction with Yb^3＋ was investigated. The results of the UV-Vis absorption spectroscopic investigation indicate that Yb^3＋ would be coordinated with carboxylate oxygen of two propionic acid groups of the heme group in an MP-11 molecule, leading to the increase in the non-planarity of the porphyrin ring of the heme group, the decrease in the energy for the π-π transition and the reduction in the electron transition probability. Thus, after the addition of Yb3^~ , the position of the Soret band of MP-11 in the UV-Vis absorption spectrum of MP-11 was red-shifted by 10 nm and its absorbance was reduced by 35%. Although NaCl can increase the aggregation extent of MP-11 molecules, the existence of a large amount of Na^＋ ions would reduce the interaction between Yb^3＋ and MP-11. Thus, after addition of Yb^3＋ , the position of the Soret band was not changed and its absorbance was only reduced by 5%. Methanol can reduce the aggregation extent of MP-11 molecules and thus, increase the exposure extent. Therefore, methanol can increase the absorbance of the Soret band with a certain extent.