Tarasevich Barbara J, Lea Scott, Bernt William, Engelhard Mark, Shaw Wendy J
Pacific Northwest National Laboratory, 908 Battelle Boulevard, Richland, Washington 99352, USA.
J Phys Chem B. 2009 Feb 19;113(7):1833-42. doi: 10.1021/jp804548x.
The interactions of proteins at surfaces are of great importance to biomineralizaton processes and to the development and function of biomaterials. Amelogenin is a unique biomineralization protein because it self-assembles to form supramolecular structures called "nanospheres", spherical aggregates of monomers that are 20-60 nm in diameter. Although the nanosphere quaternary structure has been observed in solution, the quaternary structure of amelogenin adsorbed onto surfaces is also of great interest because the surface structure is critical to its function. We report studies of the adsorption of the amelogenin onto self-assembled monolayers (SAMs) with COOH and CH(3) end group functionality and single crystal fluoroapatite (FAP). Dynamic light scattering (DLS) experiments showed that the solutions contained nanospheres and aggregates of nanospheres. Protein adsorption onto the various substrates was evidenced by null ellipsometry, X-ray photoelectron spectroscopy (XPS), and external reflectance Fourier transform infrared spectroscopy (ERFTIR). Although only nanospheres were observed in solution, ellipsometry and atomic force microscopy (AFM) indicated that the protein adsorbates were much smaller structures than the original nanospheres, from monomers to small oligomers in size. Monomer adsorption was promoted onto the CH(3) surfaces, and small oligomer adsorption was promoted onto the COOH and FAP substrates. In some cases, remnants of the original nanospheres adsorbed as multilayers on top of the underlying subnanosphere layers. Although the small structures may be present in solution even though they are not detected by DLS, we also propose that amelogenin may adsorb by the "shedding" or disassembling of substructures from the nanospheres onto the substrates. This work suggests that amelogenin may have a range of possible quaternary structures that interact with surfaces.
蛋白质在表面的相互作用对于生物矿化过程以及生物材料的发育和功能至关重要。釉原蛋白是一种独特的生物矿化蛋白，因为它能自组装形成称为“纳米球”的超分子结构，即直径为20 - 60纳米的单体球形聚集体。尽管在溶液中已观察到纳米球的四级结构，但吸附在表面的釉原蛋白的四级结构也备受关注，因为表面结构对其功能至关重要。我们报告了关于釉原蛋白吸附到具有COOH和CH(3)端基功能的自组装单分子层（SAMs）以及单晶氟磷灰石（FAP）上的研究。动态光散射（DLS）实验表明，溶液中含有纳米球和纳米球聚集体。通过零椭偏仪、X射线光电子能谱（XPS）和外反射傅里叶变换红外光谱（ERFTIR）证明了蛋白质吸附到各种底物上。尽管在溶液中仅观察到纳米球，但椭偏仪和原子力显微镜（AFM）表明，蛋白质吸附物是比原始纳米球小得多的结构，尺寸从单体到小寡聚体。单体吸附在CH(3)表面上得到促进，小寡聚体吸附在COOH和FAP底物上得到促进。在某些情况下，原始纳米球的残余物以多层形式吸附在下层亚纳米球层之上。尽管即使DLS未检测到，小结构也可能存在于溶液中，但我们还提出，釉原蛋白可能通过纳米球上的亚结构“脱落”或分解到底物上而吸附。这项工作表明，釉原蛋白可能具有一系列与表面相互作用的可能四级结构。
