Effects of protein-polyelectrolyte affinity and polyelectrolyte molecular weight on dynamic properties of bovine serum albumin-poly(diallyldimethylammonium chloride) coacervates
Effects of protein-polyelectrolyte affinity and polyelectrolyte molecular weight on dynamic properties of bovine serum albumin-poly(diallyldimethylammonium chloride) coacervates
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DOI：
10.1021/bm049174p
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发表时间：
2005-05-01
影响因子：
6.2
通讯作者：
Jaeger, W
中科院分区：
文献类型：
--
作者：
Bohidar, H;Dubin, PL;Jaeger, W
牛血清白蛋白（BSA）和聚（二烯丙基二甲基氯化铵）（PDADMAC）自发形成，在离子强度I和pH值的范围内，致密的流体中富含两种大离子。为了研究它们的纳米结构，这些凝聚体在低I和高pH（强相互作用）或在高I和较低pH（弱相互作用）下制备，聚合物MW范围为90 K至700 K，然后通过动态光散射（DLS）和流变学检查。DLS显示出独立于聚合物MW的占主导地位且令人惊讶的快速蛋白质扩散模式;伴随着稳健的慢模式，慢1-2个数量级，其也对MW不敏感，并且无论I、pH和样品老化如何都存在。通过流变学观察到高MW敏感性的终端时间（毫秒级），这增加以及与聚电解质-蛋白质相互作用的强度。粘弹性行为也表明了一个纤细的网络，固体样在低应变，但重新形成后，剪切断裂。提出了两种模型，它们各有优点和缺点：（I）在渗流极限附近，富大离子畴分散在贫大离子畴的连续体中;（II）PDADMAC链的半稀溶液，其链间摩擦受BSA-PDADMAC缔合作用的调节。
Bovine serum albumin (BSA) and poly(diallyldimethylammonium chloride) (PDADMAC) spontaneously form, over a range of ionic strength I and pH, dense fluids rich in both macroions. To study their nanostructure, these coacervates were prepared at low I and high pH (strong interaction) or at high I and lower pH (weaker interaction), with polymer MWs ranging from 90K to 700K, and then examined by dynamic light scattering (DLS) and rheology. DLS shows a dominant and surprisingly fast protein diffusional mode independent of polymer MW; accompanied by robust slow modes, slower by 1-2 orders of magnitude, which are also insensitive to MW and are present regardless of I, pH, and sample aging. High MW sensitivity was observed by rheology for the terminal time (order of milliseconds), which increased as well with the strength of polyelectrolyte-protein interaction. Viscoelastic behavior also indicated a tenuous network, solidlike at low strain but re-forming after breakage by shear. Two models, both of which have strengths and defects, are put forward: (I) macroion-rich domains dispersed in a continuum of rnacroion-poor domains near the percolation limit and (II) a semidilute solution of PDADMAC chains with interchain friction modulated by transient BSA-PDADMAC association.