Survey of the proton affinities of adenine, cytosine, thymine and uracil dideoxyribonucleosides, deoxyribonucleosides and ribonucleosides

The kinetic method was applied to the determination of the proton affinitie s (PAs) of modified deoxy- and dideoxyribonucleosides. A correlation betwee n the measured PAs and the replacement of one of the three hydroxyl groups of the ribose unit is presented. A PA scale was obtained which shows that t he replacement of the primary or of one or both secondary hydroxyl groups o f a ribonucleoside with a hydrogen atom induces the lowering or the enhance ment of the nucleoside PA, respectively, The scale extends over a very narr ow range of similar to 2 kcal mol(-1), thus demonstrating the sensitivity o f the kinetic method in the evaluation of small differences in thermodynami c parameters. Copyright (C) 2000 John Wiley & Sons, Ltd.