National ESCA and Surface Analysis Center for Biomedical Problems, Department of Bioengineering, University of Washington, Seattle, Washington 98195, USA.
J Am Chem Soc. 2012 May 30;134(21):8750-3. doi: 10.1021/ja301711w. Epub 2012 May 18.
Extracellular biomineralization proteins such as salivary statherin control the growth of hydroxyapatite (HAP), the principal component of teeth and bones. Despite the important role that statherin plays in the regulation of hard tissue formation in humans, the surface recognition mechanisms involved are poorly understood. The protein-surface interaction likely involves very specific contacts between the surface atoms and the key protein side chains. This study demonstrates for the first time the power of combining near-edge X-ray absorption fine structure (NEXAFS) spectroscopy with element labeling to quantify the orientation of individual side chains. In this work, the 15 amino acid N-terminal binding domain of statherin has been adsorbed onto HAP surfaces, and the orientations of phenylalanine rings F7 and F14 have been determined using NEXAFS analysis and fluorine labels at individual phenylalanine sites. The NEXAFS-derived phenylalanine tilt angles have been verified with sum frequency generation spectroscopy.
细胞外生物矿化蛋白，如唾液中的护牙素，控制着羟磷灰石（HAP）的生长，而 HAP 是牙齿和骨骼的主要成分。尽管护牙素在人类硬组织形成的调控中起着重要作用，但涉及的表面识别机制仍知之甚少。蛋白-表面的相互作用可能涉及到表面原子和关键蛋白侧链之间非常特定的接触。本研究首次证明了将近边 X 射线吸收精细结构（NEXAFS）光谱与元素标记相结合来定量单个侧链取向的强大功能。在这项工作中，护牙素的 15 个氨基酸 N 端结合域被吸附到 HAP 表面，并用 NEXAFS 分析和单个苯丙氨酸位点的氟标记来确定苯丙氨酸环 F7 和 F14 的取向。NEXAFS 衍生的苯丙氨酸倾斜角度已通过和频产生光谱得到验证。
