Asymmetry, Phase Transitions, and Temperature-Dependent Molecular Transport in Cell Membranes
Event details
| Date | 20.10.2023 |
| Hour | 14:00 › 15:00 |
| Speaker | Prof. Hai-Lung Dai, Institute for Membranes and Interfaces, Temple University, Philadelphia, PA (USA) |
| Location | |
| Category | Conferences - Seminars |
| Event Language | English |
BIOENGINEERING SEMINAR
Abstract:
Second Harmonic Light Scattering, a surface-sensitive phenomenon, can be used to observe molecular adsorption and transport at cell membranes with real-time and spatial resolutions. From transport rate measured for a hydrophobic ion (Malachite Green) as a function of temperature in the range of 10-40ºC through 1) the cytoplasmic membrane (CM) of the Gram-negative bacterium E. coli and 2) the membrane of liposomes made of E. coli CM lipid extract, we have observed dramatic decrease of molecular transport rate from human body temperature to refrigerator temperature. The temperature dependent transport rates display effects of two phase transitions from a gel to a mixed to a liquid-disordered phase. The adsorption equilibrium constant measured as a function of temperature also displays characteristics mimicking the two phase-transitions, but the transition temperatures for the two leaflets of the liposome membrane are determined to differ. Based on experimentally measured adsorption equilibrium constants at the pure gel vs the pure liquid-disordered phases, ratios of gel vs liquid-disordered phases in the mixed phase of the two leaflets can be independently determined. All experimental measurements on the adsorption equilibrium at the leaflet surface and the ratio of the gel vs liquid-disordered phases show that the structures of the two leaflets of this liposome are asymmetric.
Bio:
Prof. Hai-Lung Dai, is Laura H. Carnell Professor of Chemistry and Director of the Institute for Membranes and Interfaces at Temple University in Philadelphia, PA (USA).
Research interests:
Nonlinear optical and spectroscopic/microscopic studies of the structure and dynamics of surfaces and interfaces, colloidal particles, aerosols, nanoparticles, micelles, liposomes and biological cells; structure and dynamics of new energy materials including RTIL, DSSS, and organic crystals and thin films; energy transfer and reactions of highly excited molecules.
Education:
1981-1984 Postdoctoral researcher, Massachusetts Institute of Technology
1981 Ph.D. University of California, Berkeley
1974 B.S. National Taiwan University
Selected Awards:
Ellis Lippincott Award in Spectroscopy, Optical Society of America, Society of Applied Spectroscopy, and Coblentz Society. Langmuir Lecturer Award, American Chemical Society Division of Colloid and Surface Chemistry. Coblentz Award in Molecular Spectroscopy. H.L. Dai Festschrift, Journal of Physical Chemistry. American Chemical Society Philadelphia Section Award. Fellow, American Chemical Society. Fellow, American Physical Society. Guggenheim Fellow. Dreyfus Teacher-Scholar Award. Sloan Fellow. Michael P. Malone International Leadership Award, Association of Public and Land Grant Universities. Knight of the Order of the Italian Star, Government of Italy. Distinguished Alumni Award, National Taiwan University.
Abstract:
Second Harmonic Light Scattering, a surface-sensitive phenomenon, can be used to observe molecular adsorption and transport at cell membranes with real-time and spatial resolutions. From transport rate measured for a hydrophobic ion (Malachite Green) as a function of temperature in the range of 10-40ºC through 1) the cytoplasmic membrane (CM) of the Gram-negative bacterium E. coli and 2) the membrane of liposomes made of E. coli CM lipid extract, we have observed dramatic decrease of molecular transport rate from human body temperature to refrigerator temperature. The temperature dependent transport rates display effects of two phase transitions from a gel to a mixed to a liquid-disordered phase. The adsorption equilibrium constant measured as a function of temperature also displays characteristics mimicking the two phase-transitions, but the transition temperatures for the two leaflets of the liposome membrane are determined to differ. Based on experimentally measured adsorption equilibrium constants at the pure gel vs the pure liquid-disordered phases, ratios of gel vs liquid-disordered phases in the mixed phase of the two leaflets can be independently determined. All experimental measurements on the adsorption equilibrium at the leaflet surface and the ratio of the gel vs liquid-disordered phases show that the structures of the two leaflets of this liposome are asymmetric.
Bio:
Prof. Hai-Lung Dai, is Laura H. Carnell Professor of Chemistry and Director of the Institute for Membranes and Interfaces at Temple University in Philadelphia, PA (USA).
Research interests:
Nonlinear optical and spectroscopic/microscopic studies of the structure and dynamics of surfaces and interfaces, colloidal particles, aerosols, nanoparticles, micelles, liposomes and biological cells; structure and dynamics of new energy materials including RTIL, DSSS, and organic crystals and thin films; energy transfer and reactions of highly excited molecules.
Education:
1981-1984 Postdoctoral researcher, Massachusetts Institute of Technology
1981 Ph.D. University of California, Berkeley
1974 B.S. National Taiwan University
Selected Awards:
Ellis Lippincott Award in Spectroscopy, Optical Society of America, Society of Applied Spectroscopy, and Coblentz Society. Langmuir Lecturer Award, American Chemical Society Division of Colloid and Surface Chemistry. Coblentz Award in Molecular Spectroscopy. H.L. Dai Festschrift, Journal of Physical Chemistry. American Chemical Society Philadelphia Section Award. Fellow, American Chemical Society. Fellow, American Physical Society. Guggenheim Fellow. Dreyfus Teacher-Scholar Award. Sloan Fellow. Michael P. Malone International Leadership Award, Association of Public and Land Grant Universities. Knight of the Order of the Italian Star, Government of Italy. Distinguished Alumni Award, National Taiwan University.
Practical information
- Informed public
- Free