  Deep inelastic structure functions have been calculated by Polchinski and
Strassler in gauge/string duality introducing a hard infrared (IR) cut off in
AdS space. Here we investigate this problem using a soft IR cut off that leads
to linear Regge trajectories for mesons. We calculate the structure functions
for scalar particles in the large x regime where supergravity approximation
holds and the small x regime where massive string states contribute. We also
propose a hybrid model to calculate structure functions for fermions in the
supergravity approximation. In the deep inelastic limit our results are in
agreement with those obtained using a hard cut off.
