MOLECULAR WEIGHT FRACTIONATION AND SELF-SUPPRESSION OF COMPLEX COACERVATION
MOLECULAR WEIGHT FRACTIONATION AND SELF-SUPPRESSION OF COMPLEX COACERVATION
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DOI：
10.1002/bip.1967.360050106
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发表时间：
1967-01-01
期刊：
影响因子：
2.9
通讯作者：
MUSSELL, S
中科院分区：
文献类型：
--
作者：
VEIS, A;BODOR, E;MUSSELL, S
由于无盐等离子未分馏明胶水溶液的复杂凝聚，其pI[图像]s为5和9，从而产生了明显的分子量分馏或相分离。粘度研究表明，分馏是这样的，浓缩相倾向于保持恒定，均匀的组成。在相体积和浓度测量中看到的第二个特征是，随着混合浓度的增加，凝聚强度有明显的自抑制。这些数据是用稀相骨料模型解释的，该模型假设稀相骨料和浓随机相混合的静电自由能几乎相等。相分离的驱动力是随机相形成时熵的增加，但分离也取决于聚合物-溶剂相互作用参数[chi]，与简单凝聚的方式相同。稀相聚集体模型表明，在聚集体形成过程中发生了剧烈的分子量选择，并解释了自抑制现象。利用分馏的、低分散的高分子量明胶进行相平衡研究，强调了对浓相均匀性的要求，并指出不同分子量的聚集体可以作为不同的组分，因此[chi] P1Q1， PkQk > 0，使体系分离成3个或更多并存的相。同源聚电解质体系中几个共存相的形成以及对相均匀性的非常明显的要求表明，复杂凝聚现象是聚合物聚体生物前组织中一些重要步骤的一个很好的模型。
A marked molecular weight fractionation accompanies the demixing or phase separation resulting from the complex coacervation of mixtures of aqueous solutions of salt-free isoionic unfractionated gelatins with pI[image]s of 5 and 9. Viscosity studies show that the fractionation is such that the concentrated phase tends to maintain constant, homogeneous composition. A 2nd feature, seen in phase volume and concentration measurements, is a marked self-suppression of coacervation intensity with increasing mixing concentration. These data were interpreted in terms of a dilute-phase aggregate model which assumes nearly equal electrostatic free energies of mixing in dilute aggregate and concentrated random phase. The driving force for phase separation is the entropy increase upon formation of the random phase but demixing also depends upon the polymer-solvent interaction parameter [chi] , in the same fashion as in simple coacervation. The dilute-phase aggregate model indicates that the sharp molecular weight selection takes place in the aggregate formation atep and explains the self-suppression. Phase equilibria studies utilizing fractionated, paucidisperse high molecular weight gelatins, emphasize the requirement for concentrated phase homogeneity and indicate that aggregates of different molecular weight may act as different components, so that [chi] P1Q1, PkQk > 0, bringing about a separation of the system into 3 or more coexisting phases. The formation of several coexisting phases from a homologous polyelectrolyte system and the very marked requirement for phase homogeneity suggest that the phenomenon of complex coacervation is a very good model for some of the essential steps in the prebiologic organization of polymeric polylons.