摘要
Raman spectra of purified oxygen evolution core complexes (Pd OECC) thin films on silver mirror substrates have been taken over the frequency range of 250-3100 cm -1 by surface enhanced Raman scattering (SERS). Besides the fundamental frequency modes of β_carotene in Pd OECC, many weak peaks are observed. According to the selection rules of overtone and combination bands, most of them are attributed to the second_order Raman spectra of β_carotene. Compared with the SERS of normal Pd OECC, the SERS of Pd OECC after strong illumination shows a decrease in scattering intensity and an increase in line widths, indicating changes of conformation and micro_environment of β_carotene. The results of SERS are consistent with the changes of absorption spectrum of Pd OECC induced by strong illumination. There are no changes that can be ascribed to new vibration bands, so it is deduced that Pd OECC on the silver mirror is identical to that in the solution. In summary, SERS proved a good method to study the photodamage mechanism of photosynthesis.
利用有极高检测灵敏度的表面增强拉曼散射 (SERS)技术 ,对吸附在银镜表面上的浓度较低的纯化的放氧核心复合物 (PdOECC)薄层进行了频移在 2 5 0～ 3 10 0cm-1范围内的拉曼光谱测量 ,除得到 β_胡萝卜素分子的基频拉曼振动模外 ,在高频端还得到了许多弱峰。根据泛音和组合谱带选择定则分析 ,这些振动模式来自 β_胡萝卜素分子的高阶拉曼光谱。还进行了PdOECC在强光破坏前后的SERS光谱研究。在强光照射下 ,β_胡萝卜素分子的SERS光谱的散射强度明显降低 ,且线宽增加 ,说明强光照射不但改变了 β_胡萝卜素的构象 ,而且也改变了 β_胡萝卜素分子所处的微环境。其结果与强光照射前后吸收光谱的变化一致。另外 ,没有观察到PdOECC薄层与银镜相互作用的其他新振动峰或PdOECC中其他振动峰峰型的变化 ,可见PdOECC在银镜表面保持原来的状态。这证明SERS技术在光合作用光破坏机理研究中的可行性。
基金
The State Key Basic Research and Developmental Plan(G1998010100).
