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J R Soc Interface. 2017 Oct;14(135). pii: 20170464. doi: 10.1098/rsif.2017.0464.

Off-axis electron holography of bacterial cells and magnetic nanoparticles in liquid.

Author information

1
Division of Materials Sciences and Engineering, Ames Laboratory, Ames, IA 50011, USA tprozoro@ameslab.gov.
2
Department of Earth Science and Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK.
3
Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany.
4
Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany rdb@fz-juelich.de.

Abstract

The mapping of electrostatic potentials and magnetic fields in liquids using electron holography has been considered to be unrealistic. Here, we show that hydrated cells of Magnetospirillum magneticum strain AMB-1 and assemblies of magnetic nanoparticles can be studied using off-axis electron holography in a fluid cell specimen holder within the transmission electron microscope. Considering that the holographic object and reference wave both pass through liquid, the recorded electron holograms show sufficient interference fringe contrast to permit reconstruction of the phase shift of the electron wave and mapping of the magnetic induction from bacterial magnetite nanocrystals. We assess the challenges of performing in situ magnetization reversal experiments using a fluid cell specimen holder, discuss approaches for improving spatial resolution and specimen stability, and outline future perspectives for studying scientific phenomena, ranging from interparticle interactions in liquids and electrical double layers at solid-liquid interfaces to biomineralization and the mapping of electrostatic potentials associated with protein aggregation and folding.

KEYWORDS:

liquid cell TEM; magnetic nanoparticles; magnetotactic bacteria; off-axis electron holography

PMID:
29021160
PMCID:
PMC5665829
DOI:
10.1098/rsif.2017.0464
[Indexed for MEDLINE]
Free PMC Article

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