Abstract: The Secondary structure of earthworm Calmodulin(CaM) in thin film was measured by using FT-IR spectroscopic method and curve fitting technique, and the effects of Ca²⁺ and Tb³⁺ were investigated in detail. The results show that CaM exhibits lower content of α-helix and relatively higher contents of β-sheet and beta-turn structure in film than that in crystal or water solution. To some extent, the addition of different ratios of Ca²⁺ and Tb³⁺ induced different conformation changes, which indicates that the two ions have different combination mechanisms. Moreover, the activity to stimulate the PDE enzyme and the SDS-PAGE behavior of CaM with different metal ions were also studied. The results show that Tb³⁺ can active CaM under low concentration, but inhibit the activity of CaM under high concentration, which suggests that Tb³⁺ have different physiology role from Ca²⁺.

Key words: FTIR, CaM, secondary structure, Ca²⁺, Tb³⁺

摘要： 运用FT-IR方法的分辨率增强及曲线拟合技术对水化膜中蚯蚓钙调素CaM的二级结构以及加入不同比例Ca²⁺、Tb³⁺后CaM二级结构的变化进行了研究。结果表明，水化膜中CaM及含不同比例Ca²⁺或Tb³⁺的蛋白复合物的α-helix的含量较晶体和溶液中为低，而β-sheet和turn结构的含量相对较高。研究发现不同比例金属离子的加入，引起了CaM二级结构不同程度的变化，但各类结构在总量上观察不到明显的变化规律，且由于结合机制的不同，Ca²⁺和Tb³⁺的影响也各不相同。Tb³⁺可与CaM中的Ca结合位点结合，在一定条件下激活CaM，但在较高浓度下，Tb³⁺的结合抑制CaM的活性。

关键词: FTIR, CaM, 二级结构, Ca²⁺, Tb³⁺