Browsing by Subject "microscopy"

Now showing 1 - 3 of 3

Adhesion promotes phase separation in mixed-lipid membranes
(European Physical Society, 2008-11) Gordon, Vernita D.; Deserno, M.; Andrew, C. M. J.; Egelhaaf, S. U.; Poon, W. C. K.
We investigate the interplay of domain formation and adhesion in mixed-lipid membranes. Giant unilamellar vesicles consisting of two- and three-component lipid mixtures are studied using confocal fluorescence microscopy. Upon driving the system towards the demixing transition, phase separation is invariably found to occur first in regions where membranes adhere to one another, despite identical lipid headgroups and negligible curvature effects. We propose a simple generic mechanism based on the suppression of thermal shape fluctuations to explain these observations. Our findings suggest novel possibilities by which biomembranes can create and utilize lateral lipid heterogeneities.
Broadband boundary effects on Brownian motion
(2015-12) Mo, Jianyong; Simha, Akarsh; Raizen, Mark G.; Mo, Jianyong; Simha, Akarsh; Raizen, Mark G.
Brownian motion of particles in confined fluids is important for many applications, yet the effects of the boundary over a wide range of time scales are still not well understood. We report high-bandwidth, comprehensive measurements of Brownian motion of an optically trapped micrometer-sized silica sphere in water near an approximately flat wall. At short distances we observe anisotropic Brownian motion with respect to the wall. We find that surface confinement not only occurs in the long time scale diffusive regime but also in the short time scale ballistic regime, and the velocity autocorrelation function of the Brownian particle decays faster than that of a particle in bulk fluid. Furthermore, at low frequencies the thermal force loses its color due to the reflected flow from the no-slip boundary. The power spectrum of the thermal force on the particle near a no-slip boundary becomes flat at low frequencies. This detailed understanding of boundary effects on Brownian motion opens a door to developing a 3D microscope using particles as remote sensors.
Protocols in the observing of sealing mechanisms in crayfish giant axons
(2019-05) Kang, Edward; Bittner, George
Polyethylene glycol (PEG) is a fusion agent that is integral to the present and future work of our lab. However, not much is understood about how PEG interacts with membrane in damaged axons. Previous research finds that PEG seals cut axons instantly upon application. To better understand the membrane dynamics that result in this phenomenon, we have developed protocols to examine the effects of PEG on crayfish giant axons after injury.