Xia J, Dubin P L, Kokufuta E, Havel H, Muhoberac B B
Department of Chemistry, Indiana University-Purdue University, Indianapolis 46202, USA.
Biopolymers. 1999 Aug;50(2):153-61. doi: 10.1002/(SICI)1097-0282(199908)50:2<153::AID-BIP4>3.0.CO;2-4.
Quasi-elastic light scattering (QELS), electrophoretic light scattering (ELS), CD spectroscopy, and azide binding titrations were used to study the complexation at pH 6.8 between ferrihemoglobin and three polyelectrolytes that varied in charge density and sign. Both QELS and ELS show that the structure of the soluble complex formed between ferrihemoglobin and poly(diallyldimethylammonium chloride) [PDADMAC] varies with protein concentration. At fixed 1.0 mg/mL polyelectrolyte concentration, protein addition increases complex size and decreases complex mobility in a tightly correlated manner. At 1.0 mg/mL of greater protein concentration, a stable complex is formed between one polyelectrolyte chain and many protein molecules (i.e., an intrapolymer complex) with apparent diameter approximately 2.5 times that of the protein-free polyelectrolyte. Under conditions of excess polyelectrolyte, each of the three ferrihemoglobin-polyelectrolyte solutions exhibits a single diffusion mode in QELS, which indicates that all protein molecules are complexed. CD spectra suggest little or no structural disruption of ferrihemoglobin upon complexation. Azide binding to the ferrihemoglobin-poly(2-acrylamide-2-methylpropanesulfonate) [PAMPS] complex is substantially altered relative to the polyelectrolyte-free protein, but minimal change in induced by complexation with an AMPS-based copolymer of reduced linear charge density. The change in azide binding induced by PDADMAC is intermediate between that of PAMPS and its copolymer.
采用准弹性光散射（QELS）、电泳光散射（ELS）、圆二色光谱（CD）和叠氮化物结合滴定法，研究了高铁血红蛋白与三种电荷密度和电荷符号不同的聚电解质在pH 6.8时的络合情况。QELS和ELS均表明，高铁血红蛋白与聚二烯丙基二甲基氯化铵[PDADMAC]形成的可溶性络合物的结构随蛋白质浓度而变化。在聚电解质浓度固定为1.0 mg/mL时，添加蛋白质会以紧密相关的方式增加络合物大小并降低络合物迁移率。在蛋白质浓度为1.0 mg/mL或更高时，一条聚电解质链与多个蛋白质分子之间会形成稳定的络合物（即聚合物内络合物），其表观直径约为无蛋白质聚电解质的2.5倍。在聚电解质过量的条件下，三种高铁血红蛋白 - 聚电解质溶液在QELS中均表现出单一扩散模式，这表明所有蛋白质分子均已络合。CD光谱表明，络合后高铁血红蛋白的结构几乎没有或没有受到破坏。与无聚电解质的蛋白质相比，叠氮化物与高铁血红蛋白 - 聚（2 - 丙烯酰胺 - 2 - 甲基丙烷磺酸盐）[PAMPS]络合物的结合发生了显著变化，但与线性电荷密度降低的基于AMPS的共聚物络合所引起的变化最小。PDADMAC引起的叠氮化物结合变化介于PAMPS及其共聚物之间。
