Urea-induced drying of carbon nanotubes suggests existence of a dry globule-like transient state during chemical denaturation of proteins

Atomistic dynamics simulations of purely hydrophobic carbon nanotubes in 8 M urea are performed to dissect the role of dispersion interactions in the denaturing power of urea. The enhanced population of urea and a paucity of water in proximity of nanotubes suggest that the stronger dispersion interaction of urea than water with nanotube triggers drying of its interior. The preferential intrusion of urea over water within nanotube interiors irrespective of their diameters directly implies a "dry globule"-like transient intermediate formation in the initial stage of protein unfolding in urea. © 2010 American Chemical Society.