Limiting Proportions of Hydrations in Irradiated RNA Molecules

The reaction kinetics of irradiated RNA molecules is analysed for the cases when dimer formation (not splitting) and hydration of uracil residues take place. After a sufficient time has elapsed, such molecules consist entirely of dimers and hydrated sites, at which time it is of interest to know the average (over an ensemble of molecules) proportion of hydrated sites. This average is obtained (i) exactly as a function of molecule length and, (ii) to any desired accuracy for infinitely long molecules.