  Semi-exclusive and exclusive processes are becoming more and more important
in high energy physics since they are excellently suited to study the internal
hadronic structure. To analyze such processes the knowledge of the hadron
distribution amplitudes, which are universal for different reactions, is
essential. Only rather indirect information on these nonperturbative functions
can be obtained from measurements. In this work we report on a lattice QCD
computation of moments of nucleon distribution amplitudes using suitable
three-quark operators. However, these operators have to be renormalized and the
mixing is even more complicated than in the continuum. Using the symmetry group
of the hypercubic lattice we therefore derive and implement irreducibly
transforming three-quark operators, which allow us to control the mixing
pattern and will finally lead to quantitative predictions in the MSbar scheme.
We present preliminary results for leading-twist and next-to-leading twist
nucleon distribution amplitudes based on the QCDSF/UKQCD simulations with 2
flavors of dynamical clover fermions.
