Abstract:

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.

SERS观察在Pd OECC薄膜中B-胡萝卜素的基频和高阶拉曼模
刘玉龙1 刘金全1 朱恪1 杨国桢1 单际修2  李良璧2   匡廷云2

（1.  中国科学院物理研究所光物理开放实验室，北京100080；
2.  中国科学院植物研究所光合作用基础开放实验室，北京100093）

摘要：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(Pd OECC)薄层进行了频移在250～3 100 cm-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Pd OECC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Pd OECC薄层与银镜相互作用的其他新振动峰或Pd OECC中其他振动峰峰型的变化,可见Pd OECC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.

关键词： SERS；光合作用；光破坏；β-胡萝卜素；基频和高阶拉曼模

Key words: SERS, photosynthesis, photodamage, β-carotene, fundamental and high order Raman modes