Lundin Maria, Sandberg Tomas, Caldwell Karin D, Blomberg Eva
Surface and Corrosion Science, Department of Chemistry, Royal Institute of Technology, Drottning Kristinas väg 51, SE-10044 Stockholm, Sweden.
J Colloid Interface Sci. 2009 Aug 1;336(1):30-9. doi: 10.1016/j.jcis.2009.03.061. Epub 2009 Apr 5.
The effect of bovine serum albumin (BSA) as impurity in a commercial bovine submaxillary gland mucin preparation (BSM; Sigma M3895) on the adsorption of BSM to hydrophilic surfaces (mica and silica) has been studied in terms of adsorption kinetics, amount and structure of the formed adlayer. The Surface Force Apparatus (SFA) was used to gain information about the extended and compressed structure of adsorbed "as received" BSM, purified BSM, BSA extracted from the "as received" BSM and mixtures of the latter purified proteins. The adsorbed amount was estimated using a combination of X-ray Photoelectron Spectroscopy (XPS), Enzyme-Linked Immuno Sorbent Assay (ELISA), Enzyme-Linked Lectin Assay (ELLA), Dual Polarization Interferometry (DPI) and Quartz Crystal Microbalance (QCM-D) measurements. Under the used conditions, purified BSM showed very low affinity for silica and only small amounts were found to adsorb on mica. Initially, the BSM molecules adopted an extended conformation on the mica surface with tails extending into the bulk phase. These tails were irreversibly compressed into a very thin (10A) layer upon applying a high load. "As received" BSM formed considerably thicker compressed layers (35A); however, the extended layer structure was qualitatively the same. When mixtures of purified BSM and BSA were coadsorbed on mica, a 9wt-% albumin content gave a comparable layer thickness as the "as received" BSM and from XPS data we draw the conclusion that the albumin content in the layer adsorbed from "as received" BSM was approximately 5wt-%. Adsorption from an equal amount of BSM and BSA revealed that even though the amount of BSM is scarce in the mixed layer, the few BSM molecules have a drastic effect on the adsorbed thickness and structure. Clearly, this study shows the importance of characterizing the mucin used since differences in purity give rise to different adsorption behaviours in terms of both adsorbed amount and layer structure.
研究了市售牛颌下腺粘蛋白制剂（BSM；Sigma M3895）中作为杂质的牛血清白蛋白（BSA）对BSM在亲水性表面（云母和二氧化硅）上吸附的影响，涉及吸附动力学、形成的吸附层的量和结构。使用表面力仪（SFA）获取有关“原样”BSM、纯化的BSM、从“原样”BSM中提取的BSA以及后两种纯化蛋白质混合物的吸附伸展和压缩结构的信息。结合X射线光电子能谱（XPS）、酶联免疫吸附测定（ELISA）、酶联凝集素测定（ELLA）、双偏振干涉测量（DPI）和石英晶体微天平（QCM-D）测量来估算吸附量。在所使用的条件下，纯化的BSM对二氧化硅的亲和力非常低，仅发现少量吸附在云母上。最初，BSM分子在云母表面呈伸展构象，尾部延伸到本体相中。施加高负载后，这些尾部不可逆地压缩成非常薄（10埃）的层。“原样”BSM形成的压缩层要厚得多（35埃）；然而，伸展层结构在定性上是相同的。当纯化的BSM和BSA的混合物共吸附在云母上时，9wt-%的白蛋白含量产生的层厚度与“原样”BSM相当，并且根据XPS数据我们得出结论，从“原样”BSM吸附的层中白蛋白含量约为5wt-%。等量的BSM和BSA的吸附表明，即使混合层中BSM的量很少，但少数BSM分子对吸附厚度和结构有显著影响。显然，这项研究表明了表征所用粘蛋白的重要性，因为纯度差异会导致在吸附量和层结构方面出现不同的吸附行为。
