  We study deep inelastic scattering (DIS) of charged leptons from polarised
spin-1/2 hadrons in terms of the gauge/gravity duality. We calculate the
structure functions related to spin-1/2 fermionic operators of ${\cal {N}}=4$
SYM theory in the planar limit and at strong coupling. Specifically, we focus
on the twist-3 operator which is dual to a certain dilatino mode and gives the
leading contribution to the hadronic tensor. We consider the Bjorken variable
within the parametric range $\lambda^{-1/2}_{SYM} \ll x < 1$ where the
supergravity dual description holds. From dimensional reduction of type IIB
supergravity on the five-sphere, we derive the interaction terms involving two
dilatini and a massless vector field mode. This vector field is a linear
combination of certain components of the graviton and the four-form potential.
The angular integrals on the five-sphere lead to selection rules for the
interactions with important consequences on the dynamics. This implies the
existence of new terms contributing to the structure functions that we
explicitly calculate. The leading contribution comes from the Pauli term,
followed by the contributions from the new terms we found.
