Evidence for a new transition in polyribonucleotides from raman optical activity

Abstract

Vibrational Raman optical activity (ROA) measurements are reported on single-stranded poly(rA) and double-stranded poly(rA)·poly(rU) in the temperature range 2 -45 • C. The intensities of one ROA couplet in poly(rA) (centred at ca 1329 cm −1 and sensitive to sugar-base conformation) and three in poly(rA)·poly(rU) (two centred at ca 1252 and 1339 cm −1 and sensitive to sugar-base conformation, and one centred at ca 1681 cm −1 and sensitive to base stacking geometry) are plotted as a function of temperature. All four plots reveal a sharp glass-like transition at ca 15 -18 • C which appears to embrace the entire biopolymer. Since both single-and double-stranded polyribonucleotides show the transition, it does not appear to be primarily associated with base-pair opening. Differential scanning calorimetry failed to reveal any latent heat, which suggests that it is not a simple first-order transition. The possibility that the transition might be associated with a freezing of motions between conformational substates, perhaps in conjuction with changes in water structure, is discussed.

Vibrational optical activity

“…This sensitivity of ROA to dynamic aspects of biomolecular structure has proved valuable in monitoring the partially structured intermediate states accessed by proteins as they are induced to unfold under the influence of heat and/or reduced pH [61], and in detecting glass-like transitions in nucleic acids [110]. These special attributes of ROA are providing a new perspective on the important problem of protein misfolding and disease.…”

Recent Trends in Chiroptical Spectroscopy: Theory and Applications of Vibrational Circular Dichroism and Raman Optical Activity

“…Nevertheless, the first ROA spectra of single‐stranded polynucleotides were reported already in 1997, followed by other molecules including double‐stranded DNA . The spectra provided insight into polynucleotide conformational dynamics . Theoretical studies of the link between the spectra and the structure are rather rare so far …”

“…[193] The spectra provided insight into polynucleotide conformational dynamics. [194] Theoretical studies of the link between the spectra and the structure are rather rare so far. [195] An interesting chapter in the spectroscopy was ROA measurement of whole viruses.…”

Raman optical activity: An incisive probe of chirality, and of biomolecular structure and behaviour

“…This enhanced sensitivity of ROA to dynamic aspects of biomolecular structure has proved valuable in monitoring the partially structured intermediate states accessed by proteins as they are induced to unfold under the influence of heat and/or reduced pH [37,40], and in detecting glass-like transitions in nucleic acids [41]. These special attributes of ROA are also providing a new perspective on the important problem of protein misfolding and disease.…”