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CAMP Professor Igor Sokolov: From Biophysics
to Nanotechnology
CAMP
Professor Igor Sokolov and his group, in the Department of Physics
at Clarkson University, are studying a variety of phenomena related
to biophysics and nanotechnology. Most of Professor Sokolov's research
involves novel use of Scanning Probe Microscopy (SPM), which is
also known as Atomic Force (AFM) and Scanning Tunneling (STM) microscopy.
The following are brief descriptions of Professor Sokolov's research
topics.
Mechanics
of Human Epithelial Cells
Professor Sokolov, together with Professor Woodworth of Clarkson
University's Department of Biology, is studying the mechanical properties
of human epithelial cells (those found in skin and other tissue
that lines the surfaces in our body). The decrease in elasticity
of epithelial tissues with ageing contributes to many human diseases.
This change was previously explained by the increase in crosslinking
of extracellular matrix proteins that normally provide elasticity.
In their work, Professor Sokolov and his group show that individual
human epithelial cells also become significantly more rigid during
ageing in vitro. Using Atomic Force Microscopy (AFM), they found
that each cell has at least three areas of different rigidity: the
area over the nucleus, the cytoplasm, and the cell edge. The Young's
modulus for each area is consistently 2-4 times higher in old cells
than in young cells. Furthermore, they developed a novel method
for direct visualization of the cytoskeleton of ageing cells using
the AFM. Using that method they can demonstrate that increased rigidity
is associated with a higher density of the cytoskeleton fibers in
both cytoplasmic and edge areas.
Going beyond merely cosmetic concerns, these insights may inspire
new directions in treating age-related diseases, such as hardening
of the arteries, joint stiffness, cataracts, Alzheimer's disease,
and dementia.
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Figure
3. One can clearly see the strong dependence on pH. Studying
these forces for various ionic strengths, position of the
pad, etc., one can obtain a force profile of the surface on
a nanometer scale. This information is important to study,
predict, and optimize various processes involving surface
interactions.
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Enhancing
Bioremediation: Study of Nanoscale Force Interaction between NAPL
and Bacteria
Professor
Sokolov and Ph.D. student Venkatesh Subba-Rao, together with Professors
Stefan Grimberg and Anja Mueller are studying the problem of optimization
of bioremediation of oil contamination.. Spills of organic solvents
in the environment may result in the formation of nonaqueous-phase
liquids (NAPL) in the subsurface. Coal tars or chlorinated solvents
are two NAPLs common at industrial sites in the USA and around the
world, contaminating large amounts of groundwater and ecosystems.
Most of these NAPLs contain known or suspected carcinogens, which
may accumulate in the food chain. Bioremediation is thought to be
one of the most promising technologies for NAPL remediation. However
up to now, its performance is still rather unpredictable. While
significant progress has been made in identifying organisms responsible
for contaminant degradation even at high contaminant concentrations,
little is known about key factors that influence NAPL remediation.
The group's research goal is to understand the role of the bacterial
surface properties in bioremediation. Furthermore they are trying
to identify polymers that induce interfacial property changes and
determine their net significance towards enhancing bioavailability.
The research focuses on coal tars and creosote as model NAPLs. By
functionalizing an AFM tip with NAPL, they will be able to quantify
the heterogeneity of NAPL/bacteria interactions as well as to identify
specific polysaccharides at the cell membrane that dominate interfacial
property changes. Their initial results have shown non trivial interactions
between NAPL and a bacterial surface. Professor Sokolov's previous
work includes a study of the heterogeneity of electrical charge
on the surface of Shewanella putrefaciens, bacteria used for bioremediation
of heavy metals in water.
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