Mechanical measurement of the unfolding of a protein

• Published in: Europhysics letters Vol. 35; no. 8; pp. 633 - 638
• Main Author: Zocchi, G
• Format: Journal Article
• Language: English
• Published: IOP Publishing 10.09.1996; EDP Sciences
• Subjects: 07.07.Df; 36.20.Ey; 87.15.He
• ISSN: 0295-5075; 1286-4854
• DOI: 10.1209/epl/i1996-00163-6

We report the first mechanical measurement of the reversible unfolding of protein molecules. The molecules are confined between a flat plate and a $\rm 10~\mu~m$ sphere, and we measure the displacement of the sphere caused by the unfolding of the molecules in denaturing agents. In the case of bovine serum albumin, this "mechanical” size of the protein increases by 9 nm (a doubling of the folded dimensions) in strong denaturants. The present technique measures a size which is the maximum extent of the molecules, and is thus complementary to other existing methods which measure a radius of gyration. It gives access to the dynamics of conformational changes over time scales from milliseconds to minutes.