NONCOINCIDENCE SPLITTING OF THE 1505 CM(-1) ADENINE BASE VIBRATION ISDUE TO COUPLING TO WATER VIA HYDROGEN-BONDING

We have observed a noncoincidence splitting of 1-2 cm(-1) for the 1505 cm(-1) adenine base vibration in poly(rA), poly(dA), 5'rAMP, and 5'dA MP. In double stranded polynucleotides, the noncoincidence splitting i s smaller than 0.3 cm(-1). Noncoincidence splitting is usually associa ted with a transition dipole-transition dipole coupling between identi cal vibrational modes on different molecules of the same species, but any angular dependent intermolecular coupling mechanism mayr cause thi s effect. It is argued that resonant vibrational coupling of 1505 cm(- 1) vibrations on different adenine bases cannot be the source of the n oncoincidence splitting. As the 1505 cm(-1) base vibration does not ha ve a large infrared absorption, it cannot be caused by transition dipo le-transition dipole coupling. We propose that a coupling via hydrogen bonding of the 1505 cm(-1) adenine base vibration to water vibrations yields the angular dependent intermolecular coupling potential. (C) 1 997 American Institute of Physics.