利用晶格动力学方法，首次计算了具有三螺旋结构的poly(dT)·poly(dA)·poly(dT)的低频振动模式.结果表明Watson-Crick氢键的呼吸模式位于90 cm-1附近，而Hoogensteen氢键除了在90 cm-1附近存在呼吸模式外，还在更低频率上存在着几个更为强烈的呼吸模式.这一结果定性地解释了低盐度下poly(dT)·poly(dA)·poly(dT)的两步热融化.

Low-frequency vibritional modes are calculated for poly (dT). poly (dA).poly(dT) triple helix by the lattice dynamical theory. Long-range interaction is found tobe important for low-ftequency vibtitional mode. Both Watson-Crick hydrogen-bond andHoogensteen hydrogen-bond have a cluster of breathing modes centered about 90 cm-1,but Hoogensteen hydrogen-bond has another several very strons breathing modes in lowerfrequency. This result explains qualitatively the melting of poly(dT).poly(dA).poly(dT) in low salt solution.