Raman spectral studies of poly(1-methylinosinic acid).

The synthesis and characterization of poly(1-methylinosinic acid) are described. Laser Raman spectra of poly (mII) were obtained as a function of temperature in D2O solution. Thermal melting profiles derived from the intensity variations of the 712, 795, 814, 986, 1333, 1509, 1550 and 1680 cm-1 bands indicate a cooperative melting temperature of 9 +/- 1 degree C. The low temperature form of poly(mII) exhibits a carbonyl frequency at 1710 cm-I which is decreased to 1680 cm-I upon melting. The Raman hypochromism in the bands reported are equal to or much larger than any reported for other nucleic acids. The data are consistent with the low temperature form of poly(mII) being an ordered single stranded unit with a high degree of basestacking. The melting profiles obtained from the uv and cd spectra are consistent with and support the Raman data. This single stranded RNA exhibits an uncharacteristic behavior in that it melts cooperatively.