Low-frequency Raman spectra of guanosine and nucleotides in ordered states: Origin of the lowest-frequency mode

Raman spectra of self-associates of guanosine were investigated in the 5–200 cm−1 region together with crystals of guanosine⋅2H2O, Na2⋅5′–UMP⋅7H2O, Na2⋅5′–GMP⋅7H2O, Na2⋅5′–CMP⋅8H2O, Na2⋅5′–dGMP⋅4H2O, and Na2⋅ATP⋅3H2O, to clarify the origin of the lowest Raman active mode of deoxyribonucleic nucleic acid (DNA). When the bases stack well to form a column, as in guanosine self-associates and crystals of guanosine and adenosine triphosphate (ATP), the spectral patterns are similar to that of DNA. The lowest-frequency bands are sharp and isolated from other bands. The result suggests that the origin of the lowest-frequency mode of DNA is assigned to the motion of bases stacked in a column. Guanosine has no phosphate groups, and ATP has no hydrogen bonds between bases in the crystal state. Therefore, neither hydrogen bonds between bases nor phosphate groups are necessary for the existence of this mode.