Evidence for a new transition in polyribonucleotides from raman optical activity

✍ Scribed by Alasdair F. Bell; Lutz Hecht; Laurence D. Barron

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 88 KB
• Volume: 30
• Category: Article
• ISSN: 0377-0486
• DOI: 10.1002/(sici)1097-4555(199908)30:8<651::aid-jrs406>3.0.co;2-f

✦ Synopsis

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.