利用Tb3+荧光光谱,通过Tb·CaM系统的特征光谱在加入Ca2+、La3+和Al3+前后荧光强度的改变,研究了pH值对Ca2+、La3+和Al3+与拟南芥钙调素 (CaM)竞争结合作用的影响.结果表明,在中性条件下,金属离子与Tb·CaM系统中Tb3+的竞争能力强弱顺序为:La3+＞Ca2+＞Al3+,与钙调素的结合力为:Tb3+＞ La3+＞Ca2+＞Al3+.在pH值等于4.5的酸性条件下,Ca2+、La3+和Al3+与Tb3+的竞争结合能力较中性条件下弱,同时,稀土在酸性条件下的竞争结合力大于Ca2+和Al3+,Al3+与CaM竞争结合能力在酸性条件下大于Ca2+.竞争实验的结果从分子水平上证实了金属离子可取代Ca·CaM中的Ca2+与钙调素产生竞争性结合,模拟Ca2+ 4·CaM的行为,且pH值对金属离子与钙调素竞争结合力产生一定影响,揭示了胞外钙调素在酸性和金属离子浓度较高的生理条件下生物效应可能的分子机制.
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