Small angle neutron scattering study of globular proteins confined in porous carbons

This article reports measurements of the concentrationdistribution of two model proteins adsorbed from aqueous solution by two different high surface area carbons, using small angle neutron and X-rayscattering (SANS and SAXS). The proteins investigated were bovine serumalbumin (67 kDa), and bovine pancreatic trypsin inhibitor (BPTI), alsoknown under the name aprotinin (6.5 kDa). The two carbon substrates wereC1, an open structured carbon aerogel derived from a resorcinolformaldehydepolymer aerogel, and C2, a commercial nanoporous carbon fromMAST Carbon (UK). Although both C1 and C2 possess a high proportion ofpores that are either closed or inaccessible to low temperature nitrogenvapour, the size distribution of the accessible pores is broad enough toaccommodate BSA molecules. In C1, which is hydrophobic, the BSA moleculesmigrate individually into pores that are compatible with their size,whereas BPTI forms clusters having the same size as BSA. With C2, thehydrophilic internal surface limits the adsorption efficiency. The strongadhesion of proteins to hydrophilic surfaces prevents diffusion of eithermolecule into the micro- and nanopores. In this sample both BSA and BPTIform large clusters.