Apparent 2-D diffusivity in a ruffled cell membrane.

Area of Science:

• Biophysics
• Cell Biology
• Surface Chemistry

Background:

• Biological cell membranes often possess complex microtopologies, such as ruffled surfaces in leukocytes, to increase surface area.
• This increased surface area can affect the measurement of molecular diffusion coefficients, leading to decreased apparent values when projected onto a 2D plane.

Purpose of the Study:

• To model and quantify the effect of membrane microtopology on molecular diffusion.
• To investigate how the apparent 2D diffusivity of molecules is influenced by the complex surface area of biological membranes.

Main Methods:

• Utilized a parameterized two-dimensional crested cycloid to simulate random-walk diffusion.
• Calculated the apparent 2D diffusivity by projecting the simulated diffusion on the ruffled membrane onto a plane.

Main Results:

• Demonstrated that apparent molecular diffusivity is reduced due to membrane ruffling.
• Quantified the relationship between apparent diffusivity and membrane area, showing a decrease to the -1.4 power.

Conclusions:

• Membrane microtopology significantly impacts measured molecular diffusion rates.
• The complex surface area of cell membranes, like those in leukocytes, leads to a predictable reduction in apparent molecular diffusivity.