The infiltration of RNA macromolecules was investigated first (Figure ). In all three cases, a clear increase in reflectivity was observed in the mid-Q range, with a more prominent fringe emerging near 0.02 Å -1 . This was particularly clear after µg/mL injection of RNA in all cases, but these changes were more modest at 3 µg/mL in the case of mRNA (Figure ). The minima of reflectivity, observed in pristine brushes near 0.035 Å -1 , were systematically found to increase and shift to 0.04 Å -1 , even for injections of 3 mg/mL RNA. Fitting of these changes were found to be particularly sensitive to an increase in hydration of the median 2 layer (directly above the initiator layer) and a reduction of its roughness (although the reduction of the roughness of all three brush layers was required to fully fit the reflectivity changes observed). Full details of the parameters used to fit these data are gathered in Table . In addition to the significant increase in hydration of the median 2 layer (inner core layer of the brush), a mild swelling of this layer was also observed in all cases. However, only the top layer of brush complexes formed in the presence of mRNA was observed.