White A P, Reeves K K, Snyder E, Farrell J, Powell J W, Mohan V, Griffey R H
Department of Physics, Reed College, Portland, OR 97202, USA.
Nucleic Acids Res. 1996 Aug 15;24(16):3261-6. doi: 10.1093/nar/24.16.3261.
Infrared spectroscopy was used to identify hydration-sensitive structural differences between single- stranded phosphorothioate (PS) and phosphodiester (PO) oligodeoxyribonucleotides. Spectra were recorded in the mid-infrared region, 500-1800 cm-1, at relative humidities between 0 and 98%; the PS and PO spectra are substantially different. The hydration effects on spectral bands in these single-stranded oligodeoxyribonucleotides is markedly different from such behavior in double- and triple-stranded oligodeoxyribonucleotides. A strong absorption occurs at 656 cm-1 in the phosphorothioate sample which is completely absent from the PO spectra. Gravimetric measurements were carried out on one PS and one PO sample to monitor and confirm hydration. The calculated BET adsorption constants [Brunauer, S., Emmett, RH. and Teller, E. (1938) J. Am. Chem. Soc., 60, 309-319] are 1.2 and 1.4 water molecules per nucleotide in the first hydration layer of PS and PO respectively. While the gravimetric data indicate that the single-stranded oligodeoxyribonucleotides hydrate very similarly to duplex DNA, the mid-infrared conformational marker bands are strikingly different from those observed for duplex DNA. In particular, the Vas of the phosphate group (PO2) at 1222 cm-1 in the single-stranded PO spectra is independent of relative humidity.
利用红外光谱法鉴别单链硫代磷酸酯（PS）和磷酸二酯（PO）寡脱氧核糖核苷酸之间对水合作用敏感的结构差异。在500 - 1800 cm-1的中红外区域，于0至98%的相对湿度下记录光谱；PS和PO光谱存在显著差异。这些单链寡脱氧核糖核苷酸中光谱带的水合作用影响与双链和三链寡脱氧核糖核苷酸中的此类行为明显不同。在硫代磷酸酯样品中，656 cm-1处出现强吸收峰，而PO光谱中完全没有该峰。对一个PS样品和一个PO样品进行了重量法测量，以监测和确认水合作用。计算得出的BET吸附常数[Brunauer, S., Emmett, RH.和Teller, E.（1938年）《美国化学会志》，60, 309 - 319]分别为PS和PO的第一水合层中每个核苷酸1.2和1.4个水分子。虽然重量法数据表明单链寡脱氧核糖核苷酸的水合作用与双链DNA非常相似，但中红外构象标记带与双链DNA中观察到的明显不同。特别是，单链PO光谱中1222 cm-1处磷酸基团（PO2）的Vas与相对湿度无关。
