Date of Award
University or Center
Atlanta University (AU)
Dr. John H. Hall, Jr.
The intensity changes and frequency shifts of the 1299, 1456, and 1578 cm-1 absorptions in the pH dependent Raman spectra of adenosine-5'-monophosphate, 8-Br-adenosine-5'- monophosphate indicate that the syn conformation inhibits protonation at N3 of adenine possibly due to steric hinderance. Our results also suggest which resonance forms are present in solution for the protonated species. The vibrational assignments for 8-Br-5'AMP are reported for pH 6.9. Ab initio STO-3G level calculations and localized molecular orbitals from the Partial Retention of Diatomic Differential Overlap method are reported for various protonated and tautomeric forms of adenine. The localized molecular orbitals indicate that the bonding patterns of the pi electrons are highly sensitive to the protonated site. This is consistent with experimental results. The conformational energy results show that N3 protonation is more favorable in the anti conformation by 32.2 kcal/mole than N3 protonation in the syn conformation, and that N3 protonation may cause a change in conformation. The 8-Cl-adenosine results show a smaller range of rotation about the base ribose bond than the range observed for adenosine and N3 protonated adenosine.
Walker, Gerald A., "Laser raman spectroscopy and thoretical calculations of biological molecules" (1986). ETD Collection for AUC Robert W. Woodruff Library. 1160.