Investigation of the magnetic properties of ferritin by AFM imaging with magnetic sample modulation |
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Authors: | Stephanie L Daniels Johnpeter N Ngunjiri and Jayne C Garno |
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Institution: | (1) Department of Chemistry and the Center for BioModular Multi-Scale Systems, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803, USA |
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Abstract: | Individual ferritin molecules can be sensitively detected using magnetic sample modulation (MSM) combined with contact mode
atomic force microscopy (AFM). To generate an oscillating magnetic field, an alternating current (AC) was applied to a solenoid
placed within the base of the AFM sample stage. When a modulated electromagnetic field is applied to samples, ferromagnetic
and paramagnetic nanomaterials are induced to vibrate. The flux of the AC electromagnetic field causes the ferritin samples
to vibrate with corresponding rhythm and periodicity of the applied field. This motion can be detected and mapped using contact
mode AFM with a soft, nonmagnetic cantilever. Changes in the phase and amplitude of the periodic motion of the sample are
sensed by the tip to selectively map vibrating magnetic nanomaterials. Particle lithography was used to create nanopatterned
test platforms of ferritin for MSM measurements. Regularly spaced structures of proteins provide precise reproducible dimensions
for multiple successive surface measurements at dimensions of tens of nanometers.
Figure Ring patterns of ferritin were used as nanoscale test platforms to characterize magnetic properties at the level of individual
proteins with AFM imaging
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Keywords: | Ferritin Magnetic sample modulation Superparamagnetic Nanomagnetism AFM Protein nanopatterns |
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