Feng Manliang, Tachikawa Hiroyasu
Department of Chemistry, Jackson State University, 1400 Lynch Street, P.O. Box 17910, Jackson, Mississippi 39217, USA.
J Am Chem Soc. 2008 Jun 11;130(23):7443-8. doi: 10.1021/ja8006337. Epub 2008 May 20.
Surface-enhanced resonance Raman scattering (SERRS) spectra of biological species are often different from their resonance Raman (RR) spectra. A home-designed Raman flow system is used to determine the factors that contribute to the difference between the SERRS and RR of met-myoglobin (metMb). The results indicate that both the degree of protein-nanoparticles interaction and the laser irradiation contribute to the structural changes and are responsible for the observed differences between the SERRS and RR spectra of metMb. The prolonged adsorption of the protein molecules on the nanoparticle surface, which is the condition normally used for the conventional SERRS experiments, disturbs the heme pocket structure and facilitates the charge transfer process and the photoinduced transformation of proteins. The disruption of the heme pocket results in the loss of the distal water molecule, and the resulting SERRS spectrum of metMb shows a 5-coordinated high-spin heme. The flow system, when operated at a moderately high flow rate, can basically eliminate the factors that disturb the protein structure while maintaining a high enhancement factor. The SERRS spectrum obtained from a 1 x 10 (-7) M metMb solution using this flow system is basically identical to the RR spectrum of a 5 x 10 (-4) M metMb solution. Therefore, the Raman flow system reported here should be useful for characterizing the protein-nanoparticles interaction and the native structure of proteins using SERRS spectroscopy.
生物物种的表面增强共振拉曼散射（SERRS）光谱通常与其共振拉曼（RR）光谱不同。使用自行设计的拉曼流动系统来确定导致高铁肌红蛋白（metMb）的SERRS和RR之间差异的因素。结果表明，蛋白质与纳米颗粒的相互作用程度以及激光照射都有助于结构变化，并导致了metMb的SERRS和RR光谱之间观察到的差异。蛋白质分子在纳米颗粒表面的长时间吸附，这是传统SERRS实验通常使用的条件，会扰乱血红素口袋结构，并促进电荷转移过程和蛋白质的光致转变。血红素口袋的破坏导致远端水分子的丢失，由此产生的metMb的SERRS光谱显示出一个五配位的高自旋血红素。当以适度高的流速运行时，流动系统基本上可以消除干扰蛋白质结构的因素，同时保持高增强因子。使用该流动系统从1×10（-7）M的metMb溶液中获得的SERRS光谱与5×10（-4）M的metMb溶液的RR光谱基本相同。因此，这里报道的拉曼流动系统对于使用SERRS光谱表征蛋白质与纳米颗粒的相互作用以及蛋白质的天然结构应该是有用的。
