2009 Annual Report Vol.37 - 中研院物理研究所 - Academia Sinica

Gelatin scaffold in red and fibroblast cells are labelled with phalladin in green and
DAPI in blue.
(5). Single Molecule Studies of Highly Confined Biological Macromolecules
The idea of confining long-chain macromolecules to surfaces has always
intrigued polymer scientists. Although lots of efforts have been made in the studies of
bulk characters of confined polymer chains, our knowledge on these molecules at
microscopic level is still very limited. Our research interests are mainly focused on
understanding the static and dynamic behaviors of highly confined polymer molecules.
Two model systems, the densely end-tethered polymer brushes and the fully adsorbed
polymers on glass-supported lipid membranes, have been intensively studied from the
single molecule aspect for past years. A novel assay has been developed to construct
high density end-grafted polymer layers on solid-liquid interface through
end-tethering DNA molecules at grafting density above 25 molecules/ Rg 2 . We have
demonstrated the first single molecule study of polymer brushes with the fluorescent
microscopy technique. We are able to visualize the conformation and the dynamics of
individual polymer molecule in this model polymer coated layer, and understand the
detailed response of the polymer brush to the shear flow. Our very recent finding also
shows the diffusivity of small molecules in such an entropy-driven brush layer could
be strongly retarded. This finding might be relevant to how this tailor-made surface
protects the substrate. Through monitoring the adsorption and the relaxation of DNA
molecules on the glass-supported charged lipid membranes, the response of individual
chain-like macromolecule to the sudden variation of the system geometry has been
studied. Following a rapid adsorption, a multi-stage anomalous swelling governed by
the interplay between the polymer topology and the dynamics of the charged lipid
molecules on the membrane has been observed for the first time. Our analysis also
shows a novel spatial-temporal pattern of the adsorbed DNA molecule at scales of a
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