Dynamics of artificial cell membranes

HAMADA Laboratory
Associate Professor：HAMADA Tsutomu

E-mail：
［Research areas］
Soft matter, Membrane biophysics
［Keywords］
Soft matter, Artificial cell, Biological membrane, Liposome, Phase separation, Molecular robotics

Skills and background we are looking for in prospective students

Basic skills of biochemical experiments, and interest in artificial cell membranes.

What you can expect to learn in this laboratory

1. Experimental skills of artificial cell membranes
2. Physical chemistry of soft matter
3. Operation of optical microscopes
4. Reading and understanding of scientific journals

【Job category of graduates】 Post-doc, Chemicals, Machinery

Research outline

Living cells are a form of self-assembled soft matter. Lipid bilayer membranes are essential components of living organisms. We i) construct artificial lipid vesicles which produce cellular dynamics, such as endocytosis and autophagy, and ii) elucidate the association of biological and nonbiological nano-materials on membrane surfaces.

1. Photo manipulation

We develop a novel system for photocontrol of dynamics of lipid vesicles through the use of a photosensitive molecule. We achieved membrane dynamics: i) triggering of lateral phase segregation, ii) budding vesicular transformation, iii) pore opening through the stabilization of bilayer edge, and iv) membrane fusion. The study could lead to a better understanding of the mechanism of membrane dynamics in living cells and may also see wider applications, such as in drug delivery and biomimetic material design.

2. Interaction with colloids

We investigate the lateral localization and dynamical motion of nano/microparticles within a membrane interface. We found that lateral heterogeneity in the membrane mediates the partitioning of nano/microparticles in a size-dependent manner. The dependence of particle diffusion on the association state was also revealed. The study may lead to a better understanding of the basic mechanisms that underlie the association of nanomaterials within a cell surface.

3. Mechanical response

We study a systematic analysis of lateral phase separation under membrane tension. We applied osmotic pressure directed toward the outside of vesicles to induce membrane tension. Microscopic observations clarified the shifts in phase structures within bilayer membranes with change in tension and temperature. We found that membrane tension can induce phase separation in homogeneous membranes. The study may provide insight into the biophysics of bilayer phase organization under tension, which is an intrinsic mechanical property of membranes.

Figure: Photo-induced fusion of lipid vesicles. (Langmuir 2017)

Key publications

1. "Photo-induced fusion of lipid bilayer membranes" Y. Suzuki, et al., Langmuir, 33, 2671 (2017).
2. "Size-dependent partitioning of nano/micro-particles mediated by membrane lateral heterogeneity" T. Hamada, et al., J. Am. Chem. Soc., 134, 13990 (2012).
3. "Domain dynamics of phase-separated lipid membranes under shear flow" T. Hamada et al., Soft Matter, 18, 9069 (2022).

Equipment

Laser scanning microscope
Optical microscope