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Atomic force microscopy study of the secretory granule lumen
1Mayo Foundation, Department of Physiology and Biophysics, Rochester, Minnesota 55905, USA.
Biophysical Journal
|November 1, 1996
Summary
Mast cell secretory granule matrices exhibit ion-dependent mechanical properties. Their elasticity changes dramatically with cation concentration, behaving like weak ion exchange resins.
Area of Science:
- Biophysics
- Cell Biology
- Materials Science
Background:
- Mast cells store cationic mediators within secretory granules.
- The mechanical properties and storage mechanism of granule matrices are not well understood.
Purpose of the Study:
- To investigate the mechanical properties of mast cell secretory granule matrices.
- To elucidate the role of cations in matrix volume and elasticity.
Main Methods:
- Atomic force microscopy was employed to measure matrix height and elastic modulus.
- Reversible volume changes were induced by varying external cation valency (La3+, Ca2+, Na+).
Main Results:
- Matrices were insoluble with an average height of 474 nm.
- Matrix volume increased tenfold with decreasing cation valency, while elastic modulus decreased 100-fold.
- Elasticity followed a pattern similar to weakly cross-linked polymers.
Conclusions:
- Mast cell granule matrices function as weak ion exchange resins.
- Ion exchange mechanisms likely govern the storage and release of cationic secretory products.