Enzyme activity is altered when proteins are adsorbed onto carbon nanotubes

Being able to attach biological molecules, such as proteins, to carbon nanotubes could lead to the development of a variety of new technologies, including novel biosensors and biomedical devices. But proteins are fairly fragile and could be damaged during attachment, with any damage likely to affect a protein’s activity. Chemists at Rensselaer Polytechnic Institute, Troy, New York, led by Jonathan Dordick, decided to investigate whether this could be a problem by attaching the enzymes a-chymotrypsin (CT) and soybean peroxidase (SBP) to carbon nanotubes and studying in detail how this affected their activity.

Dordick’s team chose CT and SBP because they are well characterised structurally and functionally, and easy to assay for activity. In addition, they are structurally unrelated, and catalyse very different types of reaction. ’This allowed us to show that our results are not specifically limited to a very small range of enzyme structures,’ says Dordick.

After attachment, the chemists tested the activity of the enzymes, and discovered that, while SBP retained much of its activity, CT became inactive. Dordick and colleagues probed the structure of the attached enzymes using Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM). They found substantial structural differences between SBP and CT. The AFM images showed SBP appearing as distinct globular structures on the carbon nanotubes, whereas CT appeared as a layer, indicating that the enzyme had unfolded and spread over the surface of the nanotubes.

Dordick’s team is continuing work in this area. ’We have found some rather astonishing properties of enzymes when adsorbed onto the nanotubes,’ Dordick told Chemistry World, ’and this has allowed us to look at some applications, including anti-fouling materials.’

Jon Evans