1. Photonic Chinese Medicine Lab, South China Normal University, Guangzhou 510631, China 2. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
Abstract：The Raman spectra of PolyA, PolyU and their double-stranded complex were measured, and the spectral changes upon the formation of double-stranded complex were studied. The experimental results show：(1) Under the experimental conditions used in the present work (0.14 mol·L-1 NaCl, 1 mmol·L-1 Tris solution, neutral pH and 15 ℃), PolyU, PolyA and PolyA·PolyU occur as random-coiled, A-single-stranded helical and A-double-stranded helical conformations, respectively. One of the main spectral differences between the latter two conformations and the former one is the Raman band near 814 cm-1 of ordered structures. Another difference is in the full width at half the maximum (i.e. FWHM) of the band near 1 100 cm-1. The FWHM of the band 1 100 cm-1 of PolyA is the same as that of PolyA·PolyU, while the band of PolyU shows remarkable broadening. In addition, we found that the conformation of PolyA is somewhat not so ordered as that of its duplex, which can be concluded from the value of I814/I1 100 of the two polynucleotides. (2) The formation of duplex makes base-base stacking interactions much stronger, and the conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some corresponding band shift. In this process, PolyU underwent more significant spectral changes than PolyA. As spectral markers, these results can be of great importance in Raman spectral signal detection of gene-chips.
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