新型银胶基底研究HSA的近红外表面增强拉曼散射

用紫外—可见两步光化学还原法，合成了等离子体共振峰出现在近红外区的新 型绿色银胶．首次用该银胶作为基底研究人血清白蛋白(HSA)的近红外表面增强拉 曼散射(NIR—SERS)，发现银胶中的线状银纳米粒子聚集体有较强的NIR—SERS效应 和生物兼容性，这为研究生物大分子的结构、构象和界面作用提供了一种较为理想 的活性基底．由所得到的NIR—SERS光谱可发现，吸附在银纳米粒子表面的HSA的肽 链骨架仍以α—螺旋结构为主，其二级构象特征基本不变；吸附作用诱导部分芳香 氨基酸残基所处的微环境发生改变，趋于银纳米粒子表面．此外，明显观察到 COO^-与C—S的特征谱带说明HSA中去质子的羧基氧、二硫桥键的硫直接与银纳米粒 子表面作用．

A Novel Silver Colloid as Substrate for Studying Near-infrared Surface Enhanced Raman Scattering of HSA

A novel colloid was synthesized using a two-step photoinduced reducting method with irradiation of ultraviolet and visible light. Characterized by a surface plasmon band in the near-infrared wavelength range, the linear nanoparticle aggregations in the silver colloid was found to occur with high efficient near-infrared surface- enhanced Raman scattering (NIR-SERS) effect and high biocompatibility for human serum albumin (HSA), which provides a potential active substrate for investigating the structure, conformation and interfacial interactions of bio-macromolecules. For the adsorbed HSA, the obtained NIR-SERS spectrum indicates that the majority of peptide- back bone adopts an ct-helical structure, which keeps the native conformation^ characteristic of normal HSA, the microenvironments of some aromatic amino residues are induced to approach the surface of silver nanoparticles. In addition, the detected Raman shifts for COO- and C-S provide evidences that deprotonated carboxyl oxygen atoms and sulphur atoms in the disulfide bridges have the direct interfacial interactions with the silver nanoparticles.