Intensity changes of base and backbone Raman modes in the B to Z transition of poly(dG-dm5C).
Raman spectroscopy was employed to investigate the temperature-induced B to Z transition of poly(dG-dm5C). The transition midpoint was about 37 degrees C for a solvent containing 20 mM Mg2+. A 10-fold change in Mg2+ concentration altered the transition midpoint by at least 60 degrees C. Raman spectra of the B and Z forms of poly(dG-dm5C) exhibited characteristics similar to those observed with poly(dG-dC). The 682 cm-1 guanine mode and 835 cm-1 backbone mode were present in the B conformation. In the Z form the intensities of these two bands decrease substantially and new peaks were observed at 621 cm-1, 805 and 819 cm-1. Several bands unique to poly(dG-dm5C) were also observed. Transition profiles of band intensity vs. temperature were determined for fourteen Raman bands. The curves of all of the base vibrations and one backbone mode had the same slope and midpoint. This indicates that conformational changes in the guanine and methycytosine bases occur concurrently.
Brown
D M
DM
School of Physics, Georgia Institute of Technology, Atlanta 30332.
Wartell
R M
RM
D008274:Magnesium; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides; D013059:Spectrum Analysis, Raman; D013696:Temperature
D011089:Polydeoxyribonucleotides; C029988:poly(dG-m(5)dC).poly(dG-m(5)dC); D008274:Magnesium