title: Measurement of the length of the a helical section of a peptide directly using atomic force microscopy.
abstract: Using atomic force microscopy (AFM), the length of the alpha-helix structure of poly-L-lysine was investigated by stretching the peptide directly, one molecule at a time. In the absence of urea, many rupturing points that seemed to be due to the breaking of some hydrogen bonds were observed in force-extension curves, while these points were never observed in the presence of 8 M urea. In the presence of 0.4 or 1.6 M urea, both force-extension curve types were observed. Total peptide elongation for each condition was calculated from force-extension curves reflecting the alpha-helix rupturing process. The experimental value of total elongation divided by the theoretical value of total alpha-helix elongation yields the alpha-helix content. This value was compatible with circular dichroism (CD) measurement results. This suggests that peptide conformation and content of the alpha-helix on a single molecule scale can be investigated by direct mechanical measurement using atomic force microscopy.
authors.affiliation: Tissue Engineering Research Center (TERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki, Japan. seiji-takeda@aist.go.jp
authors.forename: S
authors.initials: S
authors.lastname: Takeda
authors.forename: R
authors.initials: R
authors.lastname: Ptak
authors.forename: C
authors.initials: C
authors.lastname: Nakamura
authors.forename: J
authors.initials: J
authors.lastname: Miyake
authors.forename: M
authors.initials: M
authors.lastname: Kageshima
authors.forename: S P
authors.initials: SP
authors.lastname: Jarvis
authors.forename: H
authors.initials: H
authors.lastname: Tokumoto
mesh_terms: D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D018625:Microscopy, Atomic Force; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000648:ultrastructure; D008063:Thioctic Acid / Q000737:chemistry
chemical_list: D010455:Peptides; D011506:Proteins; D008063:Thioctic Acid