Wilson Craig D, Roscoe Sharon G
Department of Chemistry, Acadia University, Wolfville, Nova Scotia, Canada B4P 2R6.
Langmuir. 2004 Aug 31;20(18):7547-56. doi: 10.1021/la049478x.
The electrochemical quartz crystal nanobalance (EQCN) was used to measure the adsorption behavior of a series of lipids (stearate, oleate, linoleate, and gamma-linolenate) on a Pt surface from a phosphate buffer pH 7.0 solution at 295 K and to investigate their adsorption/displacement behavior with the proteins, beta-lactoglobulin and alpha-lactalbumin, which are known to cause fouling during milk processing. The EQCN technique and the complementary technique of cyclic voltammetry measured simultaneously provided information on the efficiency of solubilization of the proteins by these lipids. Excellent agreement was obtained for the surface concentration of adsorbed lipid from the surface charge density from cyclic voltammetry measurements and the change in mass from the EQCN frequency measurements. The Gibbs energy of adsorption showed the lipids to have a strong affinity for the platinum surface. Addition of protein to a preadsorbed lipid layer showed alpha-lactalbumin to be able to coadsorb with the lipids, while beta-lactoglobulin was able to desorb some of the unsaturated lipids but appeared to coadsorb with the saturated lipid, stearate. Addition of lipid to a preadsorbed protein layer showed the unsaturated lipids to be able to displace some of the protein. A comparison of the desorption ability of the lipids showed stearate to be very inefficient at removing protein, while the other three lipids were able to remove each of the proteins, with the order of efficiency for protein desorption being oleate > linoleate > gamma-linolenate.
采用电化学石英晶体微天平（EQCN）测定了一系列脂质（硬脂酸、油酸、亚油酸和γ-亚麻酸）在295 K下从pH 7.0的磷酸盐缓冲溶液中在铂表面的吸附行为，并研究了它们与蛋白质β-乳球蛋白和α-乳白蛋白的吸附/置换行为，已知这两种蛋白质在牛奶加工过程中会导致污染。同时采用EQCN技术和循环伏安法这一互补技术，提供了这些脂质对蛋白质增溶效率的信息。通过循环伏安测量得到的表面电荷密度和EQCN频率测量得到的质量变化，对吸附脂质的表面浓度取得了极好的一致性。吸附吉布斯自由能表明脂质对铂表面具有很强的亲和力。向预吸附的脂质层中添加蛋白质表明，α-乳白蛋白能够与脂质共吸附，而β-乳球蛋白能够解吸一些不饱和脂质，但似乎与饱和脂质硬脂酸共吸附。向预吸附的蛋白质层中添加脂质表明，不饱和脂质能够置换一些蛋白质。脂质解吸能力的比较表明，硬脂酸在去除蛋白质方面效率非常低，而其他三种脂质能够去除每种蛋白质，蛋白质解吸效率的顺序为油酸>亚油酸>γ-亚麻酸。
