Proteins Get Attached to Nanotubes

[nanoorg]

Proteins Get Attached to Nanotubes

A new way to attach proteins on to the tip of carbon nanotubes has been devised by researchers in Japan. Not only is the technique simpler than existing methods to attach biomaterials to nanotubes, it also eliminates the annoying problem of proteins attaching to the nanotube sidewalls. The protein-nanotube tips could be used to manipulate individual biomolecules and measure single biomolecule dynamics – something that is impossible with conventional silicon probes and laser tweezers.

The radius of carbon nanotube tips is about the same size as many nanobiomaterials. This means that nanotubes can be used to probe the structure of biomaterials such as proteins. What is more, CNTs have a very high mechanical strength and so can be used as force measurement probes attached to single protein molecules.

Although researchers have attached proteins to CNTs before now, the procedures they employed were complex. Moreover, there was the problem of "sidewall decoration", where proteins become attached to the sides of the nanotubes through Van de Waals attractions. Now, Yoshikazu Nakayama of Osaka University and colleagues have overcome this challenge by developing a simple route to covalently attach proteins onto the sharpened tips of multiwalled carbon nanotubes (MWCNTs) without sidewall decoration.

The researchers began by sharpening and opening the tip of a MWCNT via oxidation. Next, they bonded the open-ended tip to a carboxyl (COOH) group. The tip was then activated so that it could bond to amine (NH2) bases and a protein was covalently bonded to the tip by attaching it to the NH2.

According to the scientists, the proteins at the nanotube tip are held there by covalent forces. Since covalent forces are stronger than the Van de Waals interactions holding proteins at the nanotube sidewalls, the excess proteins can simply be washed away by rinsing the structures under running water.

Attaching the nanotube-CO-NH-protein structure to a scanning probe microscope (SPM) would allow individual biomolecules to be manipulated. "This would allow us to measure the dynamics of single biological molecules," Nakayama told nanotechweb.org. "Such manipulations have been impossible using conventional silicon probes and laser tweezers."

The Japan team says that it is now working on a process to activate the tip of a SPM thin nanotube probe to NH2 bases. "We will then demonstrate the precise manipulation of individual biomolecules using SPM," said Nakayama.

The work was reported in J. Appl. Phys.


Source: http://www.nanotechweb.org/

Story posted: 11th February 2008

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