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Preparation of Synaptic Plasma Membrane and Postsynaptic Density Proteins Using a Discontinuous Sucrose Gradient
Published on: September 3, 2014
Ultra-slow water diffusion in aqueous sucrose glasses
Bernhard Zobrist1, Vacharaporn Soonsin, Bei P Luo
1Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland. bernhard.zobrist@env.ethz.ch
Physical Chemistry Chemical Physics : PCCP
|January 14, 2011
Summary
Single sucrose particles show slow water uptake/release at low humidity and temperature, controlled by liquid-phase diffusion. This reveals glassy skins and concentration gradients, crucial for food, pharma, and atmospheric aerosol stability.
Area of Science:
- Physical Chemistry
- Materials Science
- Atmospheric Science
Background:
- Aqueous solutions are ubiquitous in nature and technology.
- Understanding water transport in concentrated solutions is vital for various applications.
- Sucrose particles serve as model systems for complex amorphous solids.
Purpose of the Study:
- To measure water uptake and release kinetics in single sucrose particles.
- To investigate the influence of low temperatures and humidities on these processes.
- To determine the translational diffusion coefficient of water in concentrated sucrose solutions.
Main Methods:
- Utilized an electrodynamic balance for contactless particle manipulation.
- Employed optical techniques with 0.2 nm sensitivity to track particle size changes.
- Simulated particle growth/shrinkage using a liquid-phase diffusion model.
Main Results:
- Observed retarded water uptake and release at low relative humidities and/or temperatures.
- Determined water diffusion coefficients as low as 10⁻²⁴ m²/s down to 203 K, deep in the glassy state.
- Inferred strong concentration gradients and the formation of glassy skins on particles.
Conclusions:
- Liquid-phase diffusion of water controls kinetics in these systems.
- Glassy skins significantly slow down water exchange, leading to long equilibration times.
- Developed a new parameterization for water diffusion relevant to food, pharmaceuticals, and atmospheric aerosols.
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