Department of Colloid Chemistry, St. Petersburg State University, Universitetsky pr. 26, 198504 St. Petersburg, Russia.
J Phys Chem B. 2011 Aug 25;115(33):9971-9. doi: 10.1021/jp204956g. Epub 2011 Aug 2.
The dynamic dilatational surface elasticity of mixed solutions of globular proteins (β-lactoglobulin (BLG) and bovine serum albumin (BSA)) with cationic (dodecyltrimethylammonium bromide (DTAB)) and anionic (sodium dodecyl sulfate (SDS)) surfactants was measured as a function of the surfactant concentration and surface age. If the cationic surfactant concentration exceeds a certain critical value, the kinetic dependencies of the dynamic surface elasticity of BLG/DTAB and BSA/DTAB solutions become nonmonotonous and resemble those of mixed solutions of proteins with guanidine hydrochloride. This result indicates not only the destruction of the protein tertiary structure in the surface layer of mixed solution but also a strong perturbation of the secondary structure. The corresponding kinetic dependencies for protein solutions with added anionic surfactants are always monotonous, thereby revealing a different mechanism of the adsorption layer formation. One can assume that the secondary structure is destroyed to a lesser extent in the latter case and hinders the formation of loops and tails at the interface. The increase of the solution's ionic strength by the addition of sodium chloride results in stronger changes of the protein conformations in the surface layer and the appearance of a local maximum in the kinetic dependencies of the dynamic surface elasticity in a relatively narrow range of SDS concentration.
球形蛋白（β-乳球蛋白 (BLG) 和牛血清白蛋白 (BSA)) 与阳离子（十二烷基三甲基溴化铵 (DTAB)）和阴离子（十二烷基硫酸钠 (SDS)）表面活性剂的混合溶液的动态扩张表面弹性作为表面活性剂浓度和表面老化的函数进行了测量。如果阳离子表面活性剂浓度超过一定的临界值，BLG/DTAB 和 BSA/DTAB 溶液的动态表面弹性的动力学依赖性变得非单调，类似于与盐酸胍混合的蛋白质溶液。该结果不仅表明混合溶液表面层中蛋白质三级结构的破坏，而且还强烈干扰二级结构。添加阴离子表面活性剂的蛋白质溶液的相应动力学依赖性始终是单调的，从而揭示了吸附层形成的不同机制。可以假设在后者情况下，二级结构的破坏程度较小，并且阻碍了界面处环和尾的形成。通过添加氯化钠增加溶液的离子强度会导致表面层中蛋白质构象发生更强的变化，并在 SDS 浓度的相对较窄范围内动态表面弹性的动力学依赖性出现局部最大值。
