Physiochemical Modeling of Vesicle Dynamics upon Osmotic Upshift

Area of Science:

• Biophysics
• Physical Chemistry
• Cell Biology

Background:

• Vesicle dynamics under osmotic stress are crucial for understanding cellular responses.
• Modeling these dynamics requires integrating volume changes, chemical reactions, and membrane transport.

Purpose of the Study:

• To develop a comprehensive model for vesicle relaxation dynamics following osmotic upshift.
• To investigate the impact of permeable and impermeable solutes on vesicle behavior.
• To analyze the influence of physical parameters on relaxation kinetics and rates.

Main Methods:

• Developed a mathematical model incorporating volume variation, chemical kinetics, and passive membrane transport.
• Simulated relaxation dynamics with impermeable osmolytes (e.g., KCl) and permeable weak acids.
• Analyzed the effects of permeability coefficients, pKa values, and vesicle size.

Main Results:

• Dynamic complexity correlates with the number of permeable species.
• Permeability coefficients and weak acid pKa values dictate system dynamics.
• Vesicle size influences relaxation rates but not the fundamental dynamics.
• Heterogeneity in vesicle size leads to stretched relaxation curves.

Conclusions:

• The model accurately predicts vesicle relaxation dynamics and can determine permeability coefficients.
• The extended model accounts for turgor pressure and non-osmotic volume in yeast cells.
• This work provides insights into solute transport and cellular responses to osmotic stress.