Characterization of DNA-protein Complex Ionogels using Small Angle Neutron Scattering, Differential Scanning Calorimetry and Rheology

摘要

We have studied the structural and thermo-mechanical properties of DNA-protein (gelatin A, GA) complex gels formed in imidazolium based ionic liquid solutions called ionogels generated has a result of first order phase transition from a complex coacervate. We probed the microscopic structure of these ionogels using Small Angle Neutron Scattering (SANS), differential scanning calorimetry (DSC) and rheological measurements. Data show that around 0.1% (w/v) GA concentration stiffening of DNA-GA complex takes place (optimum binding concentration). At higher temperature, the GA-DNA binding weakens and GA-GA interaction facilitates the reorganization of the material which on heating turns into ionosols. Ionosols when cooled to room temperature formed ionogels. The typical size of the complexes is a 150 nm (radius of gyration, R_g). SANS experiments indicate a mesh size, ξ≈3.8+0.2 nm to these gels independent of protein concentration C_(GA). Viscoelastic studies reveal that the storage and loss moduli (G' and G") values that are comparable, and the viscoelastic length ξ_(el) is typically double the mesh size of the network. It is found that these ionogels were associated with higher gel strength, and specific heat at optimum binding conditions. It is concluded that the DNA-gelatin complex ionogels comprise a unique class of designer soft material stable with respect to protein concentration change, higher gel strength and melting temperature compared to conventional gelatin gels.