Investigations aimed at clarifying the nature of geometrical domains of amidic sodium N-dodecanoyl-L-prolinate arc reported. NMR investigations on the association of aromatic solutes with the aggregates formed by the amidic surfactant in water show the selective binding of some solutes to the Z domains. Fluorescence quenching experiments allowed us to measure the aggregation number of the aggregates. SAXS experiments gave the average size and structural features of the aggregates. A NMR ROESY experiment evidenced the mosaic-like nature of the domains inside the same aggregate. (C) 2004 Elsevier Inc. All rights reserved.