Structure and function of enzymes adsorbed onto single-walled carbon nanotubes.

We have examined the structure and function of two enzymes, alpha-chymotrypsin (CT) and soybean peroxidase (SBP), adsorbed onto single-walled carbon nanotubes (SWNTs). SBP retained up to 30% of its native activity upon adsorption, while the adsorbed CT retained only 1% of its native activity. Analysis of the secondary structure of the proteins via FT-IR spectroscopy revealed that both enzymes undergo structural changes upon adsorption, with substantial secondary structural perturbation observed for CT. Consistent with these results, AFM images of the adsorbed enzymes indicated that SBP retains its native three-dimensional shape while CT appears to unfold on the SWNT surface. This study represents the first in depth investigation of protein structure and function on carbon nanotubes, which is critical in designing optimal carbon nanotube-protein conjugates.