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Infrared Nanospectroscopy of Phospholipid and Surfactin Monolayer Domains
journal contribution
posted on 2018-04-12, 17:48 authored by Bernd Kästner, C. Magnus Johnson, Peter Hermann, Mattias Kruskopf, Klaus Pierz, Arne Hoehl, Andrea Hornemann, Georg Ulrich, Jakob Fehmel, Piotr Patoka, Eckart Rühl, Gerhard UlmA main
challenge in understanding the structure of a cell membrane
and its interactions with drugs is the ability to chemically study
the different molecular species on the nanoscale. We have achieved
this for a model system consisting of mixed monolayers (MLs) of the
biologically relevant phospholipid 1,2-distearoyl-sn-glycero-phosphatidylcholine and the antibiotic surfactin. By employing
nano-infrared (IR) microscopy and spectroscopy in combination with
atomic force microscopy imaging, it was possible to identify and chemically
detect domain formation of the two constituents as well as to obtain
IR spectra of these species with a spatial resolution on the nanoscale.
A novel method to enhance the near-field imaging contrast of organic
MLs by plasmon interferometry is proposed and demonstrated. In this
technique, the organic layer is deposited on gold and ML graphene
substrates, the latter of which supports propagating surface plasmons.
Plasmon reflections arising from changes in the dielectric environment
provided by the organic layer lead to an additional contrast mechanism.
Using this approach, the interfacial region between surfactin and
the phospholipid has been mapped and a transition region is identified.
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Keywords
cell membraneplasmon interferometrynear-field imaging contrastspeciesIR spectraInfrared NanospectroscopyphospholipidSurfactin Monolayer Domainsdielectric environmentnanoscalenovel methoddomain formationcontrast mechanismML graphene substratestransition regionantibiotic surfactinforce microscopy imagingPlasmon reflectionspropagating surface plasmonsmodel system
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