AFM and TEM observations of alpha-helix to beta-sheet conformational change occurring on carbon nanotubes.
Bacteriorhodopsin (BR), which is rich in alpha-helical structure, was spread onto water with single-wall carbon nanotubes (SCNTs). After a Langmuir trough was used to apply compressive surface pressure to maintain the alpha-helices monolayer of denatured BR, the composite films comprising alpha-helices and SCNTs were transferred horizontally onto substrates. Atomic force microscopy (AFM) and fluorescence microscopy observation suggested that alpha-helices in contact with SCNTs changed into beta-sheets. High-resolution transmission electron microscopy (HR-TEM) showed 0.54 nm periodicity characteristic of the turn of alpha-helical structure in the SCNTs-free alpha-helix monolayer region and showed the 0.70 nm periodicity of beta-sheet pleated structure in the region where SCNTs were covered with unfolded BR. Unique features of carbon nanotubes that trigger conformational changes of a protein were revealed.
Sugiyama
Yukihiro
Y
Graduate School of Electronic Science and Technology, Shizuoka University 3-5-1 Jyouhoku, Hamamatsu, Shizuoka 432-8561, Japan.
Inoue
Yuji
Y
Muneyuki
Eiro
E
Haneda
Hajime
H
Fujimoto
Masayuki
M
D001436:Bacteriorhodopsins / Q000648:ultrastructure*; D018625:Microscopy, Atomic Force / Q000379:methods*; D046529:Microscopy, Electron, Transmission / Q000379:methods*; D037742:Nanotubes, Carbon; D017510:Protein Folding; D017433:Protein Structure, Secondary
D037742:Nanotubes, Carbon; D001436:Bacteriorhodopsins