2.Shape deformation of vesicle induced by chemical stimuli
3.Three dimensional analysis of lipid vesicle shape
4.Shape deformation of multi-component vesicle
5.Slow Dynamics of nano-meter-sized domains on the membrane
Synthesizing simple living cells that contain the minimal elements necessary
to perform the basic functions of life will provide insight into the biophysical
origins of life. In order to reveal physical basis of the basic functions
of cellular life, we have developed simple model vesicle systems having
membrane traffic and self-reproduction abilities. A key concept of this
model self-reproducing vesicle system is the coupling of the main-chain
transition and the shape of lipids, which controls the reduced volume of
the vesicle and the local curvature of the membrane. To date we have succeeded
to reproduce adhesion, pore formation and self-reproduction functions by
simple binary vesicles.
Adhesion of Binary Giant Vesicles Containing Negative Spontaneous Curvature Lipids
Induced by Phase Separation
Y. Sakuma, M. Imai, M. Yanagisawa, S. Komura
European Physical Journal E, 25, 403-413, (2008).
Pore Formation in a Binary Giant Vesicle Induced by Cone-Shaped Lipids
Y. Sakuma, T. Taniguchi, and M. Imai
Biophys. J. 99, 472-479 (2010).
Model System of Self-Reproducing Vesicles
Yuka Sakuma and Masayuki Imai
Phys. Rev. Lett. 107, 198101(1-5) (2011).
Shape deformation of vesicle induced by chemical stimuli
In the cellular life, the functionalities are triggered by chemical stimuli.
For instance, in various types of migrating cells, an actively generated
intracellular pH gradient exists along the axis of movement. The local
pH is also of great importance in dynamic invaginations called cristae
in mitochondria. We have investigated the chemically triggered shaped deformation
of lipid vesicles using a microinjecting technique. We believe that studying
the response of a biomimetic membrane to a local modification of its environment
will help to shed light onto the relation between cellular phenomena and
small-scale environment changes.
Lipid membrane deformation in response to a local pH modification: theory and experiments
A.-F. Bitbol, N. Puff, Yuka Sakuma, Masayuki Imai, Jean-Baptiste Fournier, and Miglena I. Angelova
Soft Matter, 8, 6073-6082 (2012).
Three dimensional analysis of lipid vesicle shape
Analysis and visualization of the shape of complex microscopic 3D biological
objects is a difficult task. The standard 2D optical or electron microscopy
provides an image of the cross-section of the object that may not capture
many of its features. We have developed and tested a new experimental methodology
to analyze the shape of lipid vesicles. 3D imaging is instrumental in the
analysis of nonaxisymmetric shapes and we used it to systematically explore
the phase diagram, which agrees well with the prediction of the area-difference
Three-Dimensional Analysis of Lipid Vesicle Transformations
A. Sakashita, N. Urakami, P. Ziherl, and M. Imai
Soft Matter, 8, 8525-8796 (2012).
Shape deformation of multi-component vesicle
One of the most fascinating properties of lipid membranes is that they
easily deform their shapes according to external circumstances, which gives
them the basic physical
aspects of biomembrane functionalities. For example, an astonishing parade of shape deformations in giant unilamellar vesicles (GUVs) is induced by the osmotic pressure difference. Another interesting feature is that biomembranes inherently comprise a multicomponent system and the constituents form heterogeneities on the membranes. For example, GUVs composed of saturated phospholipids, unsaturated phospholipids, and Chol exhibit lateral phase separations between the liquid-ordered phase and the Ld liquid-disordered phase. We have investigated shape transition kinetics coupled with phase separation.
Growth Dynamics of Domains in Ternary Fluid Vesicles
M. Yanagisawa, M. Imai, T. Masui, S. Komura and Takao Ohta
Biophysical J. 92, 115-125 (2007).
Shape deformation of ternary vesicles coupled with phase separation
M. Yanagisawa, M. Imai, and T. Taniguchi
Phys. Rev. Lett. 100, 148102(1-4) (2008).
Periodic modulation of tubular vesicles induced by phase separation
M. Yanagisawa, M. Imai, and T. Taniguchi
Phys. Rev. E 82 051928(1-9) (2010).
Slow Dynamics of nano-meter-sized domains on the membrane
In bio-membranes, assemblies of phospholipids, cholesterol and specific
proteins migrate in the sea of lipids. The lateral diffusion of these peptides,
proteins, protein complexes and lipid rafts governs the chemical reactions
among them, and hence their biological functions. Since the diffusion of
the constituents embedded in the cell membrane is a complicated problem,
the first approach is to consider the dynamical nature of Brownian objects
in a two-dimensional fluid sandwiched by three-dimensional bulk water.
We have investigated the diffusion coefficient of nanometer-sized liquid
ordered domains on vesicles using small angle neutron scattering and neutron
spin echo spectroscopy.
Nano-meter-sized domain formation in lipid membranes observed by small angle neutron scattering
T. Masui, N. Urakami and M. Imai
Eur. Phys. J. E 27, 379-389 (2008)
Diffusion of domains on nanometer sized vesicle
Y. Sakuma, N. Urakami, Y. Ogata, M. Nagao, S. Komura, T. Kawakatsu and M. Imai
J. Phys. Conf. Ser. 251, 012036(1-4) (2010).
Hydrodynamic effects on concentration fluctuations in multicomponent membranes
S. Ramachandran, S. Komura, K. Seki and M. Imai
Soft Matter 7, 1524-1531 (2011).