Petrash S, Liebmann-Vinson A, Foster M D, Lander L M, Brittain W J, Majkrzak C F
University of Akron, Institute of Polymer Science, Ohio 44325-3909, USA.
Biotechnol Prog. 1997 Sep-Oct;13(5):635-9. doi: 10.1021/bp970068r.
Neutron and X-ray reflectivity (NR and XR) have been widely used for the investigation of the structure of thin organic films. Here we demonstrate how these sensitive techniques may be applied to the study of protein adsorption to well-characterized self-assembled monolayers (SAMs) with different chemical functionalities. NR can be used for in situ study, while XR provides complementary information on the initial surfaces and dried layers measured in air after protein has been adsorbed. In situ measurements of adsorption of human serum albumin onto a hydrophilic NH2-terminated monolayer clearly show the presence of a thin layer of adsorbed protein next to the SAM. Adsorption of albumin onto a hydrophobic, deuterated, CD3-terminated SAM causes even bigger changes in the NR. Upon replacing the protein solution with protein-free buffer solution, the reflectivities from both kinds of monolayers do not change, demonstrating that the albumin adsorption is irreversible after several hours of contact with the protein solution. X-ray reflectivity measurements of dried substrates performed ex situ in air provide a lower bound estimate of the amount of protein which must be at the interface in situ. This combination of techniques provides a uniquely sensitive approach for studying changes that occur upon protein adsorption at an interface.
中子反射率和X射线反射率（NR和XR）已被广泛用于研究有机薄膜的结构。在此，我们展示了如何将这些灵敏技术应用于研究蛋白质吸附到具有不同化学功能的、特征明确的自组装单分子层（SAMs）上的情况。NR可用于原位研究，而XR则提供关于蛋白质吸附后在空气中测量的初始表面和干燥层的补充信息。人血清白蛋白吸附到亲水性NH2端基单分子层的原位测量清楚地表明，在SAM旁边存在一层吸附的蛋白质薄层。白蛋白吸附到疏水性、氘化的CD3端基SAM上会使NR发生更大的变化。用不含蛋白质的缓冲溶液替换蛋白质溶液后，两种单分子层的反射率都没有变化，这表明与蛋白质溶液接触数小时后，白蛋白的吸附是不可逆的。在空气中异位进行的干燥底物的X射线反射率测量提供了原位时必须存在于界面处的蛋白质数量的下限估计。这种技术组合为研究界面处蛋白质吸附时发生的变化提供了一种独特灵敏的方法。
