Low-frequency Raman Optical Activity of Nucleic Acids and Protein Crystals

拉曼旋光性（罗阿）被观察为右旋和左旋圆偏振入射光之间的差异拉曼光谱。这种效应预计将是占主导地位的集体振动的螺旋结构，出现在低频区域。为了对核酸、蛋白质等生物分子进行低频罗阿光谱的测量，我们设计了一套专门用于低频测量的系统，该系统由1/4 λ机械旋转波片、线偏振片、波扫描双单色器和光子计数电路组成，为了避免样品损伤，降低了激光功率，但长时间曝光会导致性能下降。我们需要透明的、大的样品，以免干扰偏振，这使得样品制备困难。我们测量了富含螺旋的蛋白质溶液，如PHIO中的聚-L-赖氨酸、胰岛素、脱铁铁蛋白和细菌视紫红质。我们找不到任何重要的信号。溶菌酶晶体的罗阿光谱显示，希望，微小的信号。我们将继续提高信噪比，在熔点以上保持螺旋结构的纯液体似乎是低频罗阿的未来目标。

Raman optical activity (ROA) is observed as the difference Raman spectra between right and lefthanded circularly polarized incident lights. This effect is expected to be dominant for collectivevibrations of helical structure, which appear in the low-frequency region. We aimed to observelow-frequency ROA of biological molecules, such as nucleic acids, and proteins.The system is specially designed for low-frequency region measurements, consisting of amechanically rotating 1/4 λ, wave plate with linear polarizer, and a double monochrofnator with wave scan, and photon counting electronics.To avoid sample damage, the laser power is lowered, nevertheless , the long time exposure resulted degradation. We need transparent, and big sample not to disturb the polarization, which makes it difficult to prepare samples.We measured a helix rich protein solutions, such as poly-L-lysine in PHIO, insulin, apoferritin,and bacterio rhodopsin. We could find no trace ofnon-trivial signals. The ROA spectra of lysozyme crystals showed, hopefully, tiny signals. We will proceed to increase the S/N ratio.The neat liquids that maintain helical structure just above the melting points seem to be a future target for low-frequency ROA.