Using an iterative solution in Laplace-Fourier space, we supply a rigorous
mathematical proof for the long-time asymptotics of reversible binding in o
ne dimension. The asymptotic power law and its concentration dependent pref
actor result from diffusional and many-body effects which, unlike for the c
orresponding irreversible reaction and in classical chemical kinetics, play
a dominant rule in shaping the approach to equilibrium.