Invented by and named for Alexander Dounce , a Dounce homogenizer or "Douncer", is a cylindrical glass tube, closed at one end, with two glass pestles of carefully specified outer diameters, intended for the gentle

homogenization Homogeneity is a sameness of constituent structure. Homogeneity, homogeneous, or homogenization may also refer to: In mathematics * Transcendental law of homogeneity of Leibniz * Homogeneous space for a Lie group G, or more general transformat ...

eukaryotic cells Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacter ...

(e.g. mammalian cells). Dounce homogenizers are still commonly used today to isolate cellular organelles. The two Dounce homogenizer pestles (known as the "loose" or "A" and "tight" or "B" pestles), have a carefully specified outer diameter, relative to the inner diameter of the cylinder. The "A" (loose) pestle has a clearance from the cylinder wall of (~0.0025 - 0.0055 in.) while the "B" (tight) pestle has a clearance of (~0.0005 - 0.0025 in.). This allows for tissue and cells to be lysed by

shear stress Shear stress, often denoted by (Greek: tau), is the component of stress coplanar with a material cross section. It arises from the shear force, the component of force vector parallel to the material cross section. '' Normal stress'', on ...

with minimal (if any) degree of heating, thereby leaving extracted organelles or heat-sensitive enzyme complexes largely intact. Typically, a soft tissue (e.g. mammalian liver) is cut or broken into smaller pieces and placed into the glass cylinder, alongside a suitable volume of an appropriate

lysis buffer A lysis buffer is a buffer solution used for the purpose of breaking open cells for use in molecular biology experiments that analyze the labile macromolecules of the cells (e.g. western blot for protein, or for DNA extraction). Most lysis buffers ...

. Homogenization is performed by a defined number of "passes" of the pestles, first with the loose pestle, then with the tight pestle, up and down the cylinder. Five to ten passes are typical. Dounce homogenizers are typically produced from borosilicate glass, but are still fragile, and should be used with care. Especially hard or tough tissues should be pre-homogenized before use in a dounce homogenizer. Eukaryotic cells with tough cell walls, such as ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungus microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have been o ...

'', cannot be directly lysed with a dounce homogenizer, unless the cell wall is first broken down (e.g. with lyticase, or zymolyase in the case of ''S. cerevisiae'').

References

{{Reflist Cell biology Biochemistry Laboratory glassware