Guzman M R, Liquier J, Taillandier E
Laboratoire BioMoCeTi, UMR CNRS 7033, Universite Paris 13, 74 rue Marcel Cachin, F93017 Bobigny Cedex, France.
J Biomol Struct Dyn. 2005 Dec;23(3):331-9. doi: 10.1080/07391102.2005.10507068.
We have studied by gravimetric measurements and FTIR spectroscopy the hydration of duplexes and triplexes formed by combinations of dA(n), dT(n), rA(n), and rU(n) strands. Results obtained on hydrated films show important differences in their hydration and in the structural transitions which can be induced by varying the water content of the samples. The number of water molecules per nucleotide (w/n) measured at high relative humidity (98% R.H.) is found to be 21 for dA(n).dT(n) and 15 for rA(n).rU(n). Addition of a third rU(n) strand does not change the number of water molecules per nucleotide: w/n=21 for rU(n)*dA(n).dT(n) and w/n=15 for rU(n)*rA(n).rU(n). On the contrary, the addition of a third dT(n) strand changes the water content but in a different way, depending whether the duplex is DNA or RNA. Thus, a loss of four water molecules per nucleotide is measured for dT(n)*dA(n).dT(n) while an increase of two water molecules per nucleotide is observed for dT(n)*rA(n).rU(n). The final hydration is the same for both triplexes (w/n=17). The desorption profiles obtained by gravimetry and FTIR spectroscopy are similar for the rA(n).rU(n) duplex and the rU(n)*rA(n).rU(n) triplex. On the contrary, the desorption profiles of the dA(n).dT(n) duplex and the triplexes formed with it (rU(n)*dA(n).dT(n) and dT(n)*dA(n).dT(n)) are different from each other. This is correlated with conformational transitions induced by varying the hydration content of the different structures, as shown by FTIR spectroscopy. Modifications of the phosphate group hydration and of the sugar conformation (S to N type repuckering) induced by decrease of the water content are observed in the case of triplexes formed on the dA(n).dT(n) duplex.
我们通过重量测量法和傅里叶变换红外光谱法研究了由dA(n)、dT(n)、rA(n)和rU(n)链组合形成的双链体和三链体的水合作用。在水合膜上获得的结果表明，它们的水合作用以及因改变样品含水量而可能引发的结构转变存在重要差异。在高相对湿度（98%相对湿度）下测得的每个核苷酸的水分子数（w/n），对于dA(n).dT(n)为21，对于rA(n).rU(n)为15。添加第三条rU(n)链不会改变每个核苷酸的水分子数：对于rU(n)*dA(n).dT(n)，w/n = 21；对于rU(n)*rA(n).rU(n)，w/n = 15。相反，添加第三条dT(n)链会改变含水量，但方式不同，这取决于双链体是DNA还是RNA。因此，对于dT(n)*dA(n).dT(n)，测得每个核苷酸损失四个水分子，而对于dT(n)*rA(n).rU(n)，观察到每个核苷酸增加两个水分子。两种三链体的最终水合作用相同（w/n = 17）。通过重量法和傅里叶变换红外光谱法获得的rA(n).rU(n)双链体和rU(n)*rA(n).rU(n)三链体的解吸曲线相似。相反，dA(n).dT(n)双链体及其形成的三链体（rU(n)*dA(n).dT(n)和dT(n)*dA(n).dT(n)）的解吸曲线彼此不同。如傅里叶变换红外光谱所示，这与不同结构的水合含量变化引起的构象转变相关。在由dA(n).dT(n)双链体形成的三链体的情况下，观察到含水量降低导致磷酸基团水合作用和糖构象（从S型到N型重新卷曲）的改变。
