We study the dynamics of a Rouse polymer chain which diffuses in a three-di
mensional space under the constraint that one of its ends, referred to as t
he slip-link, may move only along a one-dimensional line containing randoml
y placed, immobile, perfect traps. Extensions of this model occur naturally
in many fields, ranging from the spreading of polymer liquids on chemicall
y active substrates to the binding of biomolecules by ligands. For our mode
l we succeed in computing exactly the time evolution of the probability P-s
l(t) that the chitin slip-link will not encounter any of the traps until ti
me t and, consequently, that until this time the chain will remain mobile.