In order to develop highly sensitive and high-throughput protein assay systems for proteomics and biosensor systems, we elucidated the relationship between protein structure and activity on various polymer brush surfaces that immobilize proteins through different mechanisms. Various polymer brush surfaces (cationic, hydrophobic, covalent-bonding, and block-type with the cationic and zwitterionic) were synthesized via surface-initiated atom transfer radical polymerization (SI-ATRP), and both the secondary structure and activity of proteins immobilized on each surface were investigated by circular dichroism and equilibrium dissociation constant (K-d) analysis, respectively. There was a strong correlation between the stability of the secondary structures and the activity of the proteins on the polymer brush surfaces. Interestingly, proteins immobilized on the block-type polymer surface (PMPC-block-PAEMA (PMbA)) showed less structural change and higher activity than the other polymer brush surfaces. These results suggest that the prevention of the adsorption-induced structural changes has a great role in improving the activity of immobilized proteins, and underscore the potentials of zwitterionic polymers for creating ideal biointerfaces derived from the functional, surface-immobilized proteins. Such biointerfaces can be useful for improving the specificity and sensitivity of protein microarrays and biosensor systems. (C) 2015 Elsevier B.V. All rights reserved.