Roles of electrostatic interaction and polymer structure in the binding of β-lactoglobulin to anionic polyelectrolytes:: Measurement of binding constants by frontal analysis continuous capillary electrophoresis
Roles of electrostatic interaction and polymer structure in the binding of β-lactoglobulin to anionic polyelectrolytes:: Measurement of binding constants by frontal analysis continuous capillary electrophoresis
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DOI：
10.1021/la000648p
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发表时间：
2000-12-12
期刊：
影响因子：
3.9
通讯作者：
Dubin, PL
中科院分区：
文献类型：
--
作者：
Hattori, T;Hallberg, R;Dubin, PL
用前沿分析连续毛细管电泳法测定了线电荷密度相近的聚苯乙烯磺酸钠(PSS)和聚2-丙烯酰胺-2-甲基丙磺酸钠(PAMPS)与β-乳球蛋白(BLG)的结合。得到的结合等温线符合McGhee-von Hippel方程，得到了本征结合常数K-OBS和代表每个结合蛋白的聚合物链段数的结合位置大小n。BLG-PSS的K-OBS的离子强度(I)随pH的变化有两个相反的关系，即在pH为7.0时，K-OBS随I的增大而增大，而在pH为6.3时，K-OBS随I的增大而减小。相反的I依赖关系反映了具有异质带电成分的体系中静电相互作用的作用，但也表明了为蛋白质与DNA结合而提出的简单公式(logK-obs=logK-o-Z(Phi)log[M+])的不适用性。相同pH条件下，PAMPS的K-OBS始终比PSS的小得多。此外，BLG-PSS的n很小，与I和pH无关，而PAMPS的n很大，随I和pH的增加而增加，这两个结果都与BLG与PSS的结合比与PAMPS的结合更紧密一致。这种明显的对比可能是由于聚合物持续长度的影响或疏水相互作用造成的。
Frontal analysis continuous capillary electrophoresis was used to measure the binding of beta -lactoglobulin (BLG) to sodium poly( styrenesulfonate)( PSS) and sodium poly( 2-acrylamido-2-methylpropanesulfonate) (PAMPS), two strong polyanions with similar linear charge densities. The binding isotherms obtained were well-fit by the McGhee -von Hippel equation, yielding the intrinsic binding constant, K-obs, and the binding site size, n, representing the number of polymer segments per bound protein. Two opposite ionic strength (I) dependencies of K-obs for BLG-PSS were found depending upon pH, that is, increase of K-obs with I at pH 7.0, and decrease of K-obs, with I at pH 6.3. The opposite I dependencies reflected the roles of electrostatic interactions for systems with heterogeneously charged components, but also demonstrated the inapplicability of a simple formulation (log K-obs = log K-o - Z(phi) log [M+]) put forward for the binding of protein to DNA. K-obs for PAMPS was always much smaller than that for PSS at equal pH. In addition, n for BLG-PSS was small and independent of I and pH, while n for PAMPS was large and increased with I and pH, both results consistent with "tighter" binding of BLG to PSS than to PAMPS. This marked contrast may arise from the effects of polymer persistence length or from hydrophobic interactions.