Proton Transfers in Hydrogen-Bonded Nucleic Acids

摘要

A research group found that selective hydrogen bonds between nucleic acid bases are formed even in non-aqueous solvents and that base pair formation is not a specific characteristic of polynucleotides but rather of the purine and pyrimidine bases. By using infrared and nuclear magnetic resonance spectroscopy the structure distribution and thermodynamic function of the base pairs have been determined on the model systems. Recently it was found by use of the saturation transfer method in NMR that the amino and imino protons in the A-T, G-C base pair exchange with each other at a rate of 100/sec. The frequency of the proton transfer seems to relate to the ease of forming the tautomeric form. The proposed mechanism suggests that proton rearrangements by tunneling occur as an initial step. It is interesting that the phenomenon is most remarkable between adenine (A) and 5-bromouracil, a known mutagenic agent. Work consisted mainly in the design and improvement of the optical and spectroscopic system. The heart of the system is the optical parametric oscillator (OPO) which employs an angle-tuned LiNbO3 crystal pumped by a Nd:YAG laser. Improvements in fabrication techniques have resulted in LiNbO3 crystals up to 20 mm in diameter and 6 cm in length.