Aqueous solutions of guanosine 5’-monophosphate (GMP) can turn into isotropic gels by the addition of guanine (Gua). The Gua:GMP hydrogel property of including a significant amount of water opens a series of applications in the field of biocompatible nanomaterials, including the trapping of proteins and enzymes. Recently, we have investigated the properties of Gua:GMP hydrogels, with and without trapped bovine serum albumin or myoglobin by using AFM and micro DSC techniques. Depending on composition, proteins can be trapped as monomers, in the large water domains of the gel, or as protein clusters, located at the junction points of the gel fibres. On this basis, we intend to in-deep investigate with SANS structure and aggregation state of proteins trapped in the hydrogel. Experiments will be performed at the optimum matching conditions between D2O/H2O and hydrogel