Pifat G, Udovicić L, Brnjas-Kraljević J, Jürgens G, Holasek A, Herak J N
Rudjer Bosković Institute, University of Zagreb, Yugoslavia.
Chem Phys Lipids. 1988 Feb;46(2):99-105. doi: 10.1016/0009-3084(88)90119-3.
The electron spin resonance (ESR) technique was used to evaluate binding constants for Ca(II) and Mg(II) in interaction with low density lipoprotein (LDL). The Ca(II) or Mg(II) ions competed with the paramagnetic Mn(II) ions for the same binding sites of two different classes on the LDL surface. For each ion competing with Mn(II), the solutions of eight non-linear competition equations were fit to the experimental titration curves, with two adjustable parameters, the two binding constants. The derived "intrinsic" values (the values corrected for the electrolyte-induced change of the surface potential) for "strong" binding sites for Ca(II) (170 +/- 85 M-1) and Mg(II) (60 +/- 30 M-1) differ significantly from the respective value for Mn(II) (760 M-1). The values for the "weak" binding sites (18 M-1, 15 M-1 and 10 M-1 for Mn(II), Ca(II) and Mg(II), respectively are in the range of the binding constants for these ions in interaction with model membranes.
采用电子自旋共振（ESR）技术评估钙离子（Ca(II)）和镁离子（Mg(II)）与低密度脂蛋白（LDL）相互作用时的结合常数。Ca(II)或Mg(II)离子与顺磁性的锰离子（Mn(II)）竞争LDL表面两种不同类型的相同结合位点。对于每种与Mn(II)竞争的离子，将八个非线性竞争方程的解与实验滴定曲线拟合，有两个可调参数，即两个结合常数。Ca(II)（170±85 M⁻¹）和Mg(II)（60±30 M⁻¹）“强”结合位点的推导“本征”值（针对电解质诱导的表面电位变化校正后的值）与Mn(II)（760 M⁻¹）的相应值有显著差异。“弱”结合位点的值（Mn(II)、Ca(II)和Mg(II)分别为18 M⁻¹、15 M⁻¹和10 M⁻¹）在这些离子与模型膜相互作用的结合常数范围内。
