title: Surface differentiation of ferritin and apoferritin with atomic force microscopic techniques.
abstract: In the study reported herein, we differentiated the structure of ferritin from that of its demetalated counterpart, apoferritin, using field-effect-based atomic force microscopic (AFM) techniques. When ferritin was subjected to conductive-mode AFM analysis, the protein resembled a pancake with a diameter of 10 nm adsorbed on the indium-doped tin-oxide substrate with its fourfold channel perpendicular to the substrate, whereas a flat, empty cavity was revealed for apoferritin. We also attempted to verify the conformational difference with magnetic-mode AFM. However, the resulting phase images failed to differentiate the proteins due to interference from the fringe effect. Despite this, the ferritin analysis revealed a sound correlation between the surface conductivity profiles and the phase profiles. In contrast, apoferritin showed a chaotic relationship in this respect. These results not only suggest that the magnetic domain of ferritin is limited to the iron aggregate in the core, but also demonstrate that AFM is a useful tool for protein conformation analysis.
authors.affiliation: Department of Chemistry, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Ru-Hung
authors.initials: RH
authors.lastname: Ho
authors.forename: Yu-Hung
authors.initials: YH
authors.lastname: Chen
authors.forename: Chong Mou
authors.initials: CM
authors.lastname: Wang
mesh_terms: D000818:Animals; D001052:Apoferritins / Q000737:chemistry*; D005293:Ferritins / Q000737:chemistry*; D006736:Horses; D007501:Iron / Q000737:chemistry*; D060328:Magnetic Phenomena; D018625:Microscopy, Atomic Force; D011487:Protein Conformation; D013154:Spleen / Q000737:chemistry; D013499:Surface Properties
chemical_list: D005293:Ferritins; D001052:Apoferritins; D007501:Iron