Institut Universitari de Ciència Molecular, Universitat de València, Edifici d'Instituts de Paterna, P.O. Box 22085, E-46071 València, Spain.
Anal Chim Acta. 2009 Nov 3;654(1):2-10. doi: 10.1016/j.aca.2009.08.017. Epub 2009 Aug 21.
The role of electrostatics is studied in the adsorption of cationic proteins to zwitterionic phosphatidylcholine (PC) and anionic PC/phosphatidylglycerol (PG) mixed small unilamellar vesicles (SUVs). For model proteins the interaction is monitored vs. PG content at low ionic strength. The adsorption of lysozyme and myoglobin (isoelectric point, pI 7-11) is investigated in SUVs, along with changes of the fluorescence emission spectra of the cationic proteins, via their adsorption on SUVs. In the Gouy-Chapman formalism, the activity coefficient goes with the square of charge number. Deviations from the ideal model could indicate the asymmetric location of the anionic phospholipid in the bilayer inner leaflet, in mixed zwitterionic/anionic SUVs for both lysozyme- and myoglobin-PC/PG systems, in agreement with experiments and molecular dynamics simulations. Fitted effective SUV charge stays constant. Effective-formal difference increases 0.417 e.u. Effective protein charge increases as PC/PG<PC being greater for myoglobin. The molar free energies of the protein in aqueous and lipid phases increase as PC<PC/PG. Both free-energy changes are greater for myoglobin. Effective interfacial charge stays constant for anionic PC/PG SUVs being greater for myoglobin.
静电作用在阳离子蛋白吸附到两性离子磷脂酰胆碱（PC）和阴离子 PC/磷脂酰甘油（PG）混合小单层囊泡（SUV）中的作用。对于模型蛋白，在低离子强度下监测与 PG 含量的相互作用。通过阳离子蛋白在 SUV 上的吸附，研究了溶菌酶和肌红蛋白（等电点，pI7-11）在 SUV 中的吸附以及荧光发射光谱的变化。在 Gouy-Chapman 形式中，活度系数与电荷数的平方成正比。与理想模型的偏差可能表明在混合两性离子/阴离子 SUV 中，阴离子磷脂在双层内层的不对称位置，这与实验和分子动力学模拟一致。拟合的有效 SUV 电荷保持不变。有效形式差异增加 0.417 个单位。有效蛋白电荷随 PC/PG<PC 而增加，对于肌红蛋白则更大。蛋白在水相和脂相中的摩尔自由能随 PC<PC/PG 而增加。对于肌红蛋白，这两种自由能变化都更大。对于阴离子 PC/PG SUV，有效界面电荷保持不变，对于肌红蛋白则更大。
