(last update: Jan. 2009)
Center for Cell Dynamics, Department of Physics, Korea University
Sungbuk-Ku, Anam-Dong 5-1, Seoul, Korea 136-701
Tel: (82 2) 3290-4294
Fax: (82 2) 3290-3534
E-mail: (1) jinsungp AT gmail.com (2) jspark AT complex.korea.ac.kr
Positions Held
- Research assistant professor (2007~)
Center for cell dynamics (Director: Prof. Kyoung J. Lee), Department of Physics, Korea University
- Visiting Scientist (2005~)
Molecular biophyiscs laboratory, Department of Physics, Korea University
(Collaboration with Prof. Seok-Cheol Hong)
- Postdoctoral research associate (2004~2007)
Center for neurodynamics (Director: Prof. Kyoung J. Lee), Department of Physics, Korea University
- Ph. D. in Physics (2004), Korea University, Seoul, Korea
Thesis "Unusual spiral waves and their line defects in complex oscillatory system"
Advisor: Prof. Kyoung Jin Lee
- M. D. in Physics (1999), Korea University, Seoul, Korea
- B. A. in Physics (1997), Kon-Kuk University, Seoul, Korea
Research Interests
1. Nonequilibrium pattern formation in complex-oscillatory reaction-diffusion systems
During the past Ph. D. course, my experimental studies had been
focused on complex spiral waves with "line-defects" revealed in a
Belousov-Zhabotinsky (BZ) chemical reaction. The spiral wave in complex
oscillatory media are far more complicated than the much studied simple
spiral waves in simple oscillatory or excitable media. Among others,
the most salient feature of a complex periodic spiral wave is the
existence of line defects across which the phase of the local
oscillation changes by a multiple of 2 &pi .In fact, the line defects
are an essential property of complex periodic spiral waves, just as
the topological (phase) singularity is a fundamental property of a
simply periodic P-1 spiral wave. A few later, strikingly similar example
of complex spiral waves having line defects was observed in cardiac
cell cultures. This observations supports the notion that line defects
are a generic feature in a broad class of complex periodic systems
including biological systems. Our comprehensive review paper regarding
our experimental results on complex oscillatory BZ spiral waves were
published in [ Phys. Rev. E (2006)].
Figure 1. Snapshot images of spiral waves (left) and processed
images revealing their associated line-defects (right) observed
in a BZ reaction-diffusion system: (a)
P-1 spiral wave with no line defect; (b) continuous P-2 spiral wave
and associated line-defect with a shape of P-1 spiral wave; (c)
discontinuous P-2 spiral wave and associated line-defect with
a shape different from P-1 spiral. The processed images is now
revealing the existence of line defects (narrow black strips) and
domains of P-1 (black) and P-2 (bright).
Movies
- [A typical P-1 spiral wave observed in a simple (P-1) BZ reaction]
- [A P-2 spiral wave observed in a P-2 oscillatory BZ reaction]
- [A processed image showing a rotating line defect in a P-2 oscillatory BZ reaction]
- [Transition to a line defect mediated spatio-temporal chaos in a BZ system]
- [Line-defect mediated spatio-temporal chaos reproduced in a generic model system]
2. Single molecule biophysics and Cell dynamics
Currently, I am interested in two differnt biological issues,
one is to understand physical properties of cell motility in relation
with focal adhesions (FAs), and the other is a field of single molecule
biophysics studying the direct interaction between DNA-anticancer drugs,
or DNA-proteins.
A series of recent studies augments the role of glia as regulatory agents
of neuronal activity, undertaking active roles in brain computation.
Intercellular and extracellular calcium kinetics are believed to be an
important mediator for the interplay among neurons and glia. In mature
of neuron-glia co-culture systems, populations of neurons often exhibit
globally synchronized fast "calcium spikes" that are accompanied by
electrical bursts of action potentials. While the glia in the same culture
systems do often show slower "calcium wave" activities that possibly
modulate the neuronal activity. We examine the property of these slowly
propagating calcium waves in pure glia networks under various
pharmacological conditions and with different extrinsic stimulations.
Figure 2. Small irregular wavelets emerging in the wake of some dominant
pacemakers observed in a layer of purely cultured astrocytes:
(a) sequential images showing a spontaneously generated
calcium wave (96-99 sec) and small irregular wavelets circulating along
local recurrent network, and (b) local timeseries obtained from two
different sites (A and B) in (a) This experiments were conducted in
extracellular free calcium and magnesium buffer condition.
Movies
- [Synchronized neuronal calcium activities observed in a neuron-glia co-cultured layer]
- [Slowly propagating glial calcium waves observed in a neuron-glia co-cultured layer]
- [Spontaneous calcium puffs observed in a layer of purely cultured astrocytes]
Microglia are a type of glia cell, acting as representatives of
the immune system in the brain. This cell is very motile, constantly
moving to destroy pathogenes and to remove damaged neurons and plaques.
In this process, dynamic assembly and disassembly of focal adhesions
(FAs) plays a central role. FAs are large, dynamic
complex protein assembly through which cytoskeleton of cell inside
directly connect to extracellular matrix and path to transmit
mechanical force and regulatory signals. Currently, we have investigating
on (i) the relation of a directional motion of single microglia and
dynamic process of FAs,
and (ii) collective dynamics in population of microglia through
cell-to-cell signaling in the absence of external signal.
Figure 3. A typical morphology of cultured microglia with a cell body
of round shape and a long tail (left and center), and a thin trail
pattern formed spontaneously through cell-to-cell interaction
in population of cultured microglia (right).
Movies
- [ A oscillating locomotion of cultured microglia with a tripolar shape in the early stage]
- [ Single cell motility of cultured microglia with a long directional persistent motion]
- [ Single cell motility of cultured microglia with a random walk]
- [ Multi-cellular tracking in the population of highly motile microglia cells]
Single molecule biophysics has been well known as a powerful technique
to understand physical principles behind a wide range of biological
phenomena. Recently, we have investigated on salt dependent activity
of cisplatin observed through micromanipulation of a single bare DNA
molecule with magnetic tweezers. Cisplatin, a potent mutagenic
anti-cancer drug, induces a DNA kink by intra- or inter-strand
crosslinks, especially at two neighboring purine sites, which induces
apotosis of proliferating cancer cells. Now, we have studying on
modification in chromatin structure by irreversibly crosslinking DNA
and histones to understand an anti-cancer activity of cisplatin in more
realistic in vivo state - DNA compacted by wrapping the histons.
Our studies shed light on understanding the efficacy of drugs that induce
conformational changes in DNA.