The French pressure cell press, or French press, is an apparatus used in biological experimentation to disrupt the plasma membrane of cells by passing them through a narrow valve under high pressure. The French Press can also be used for disintegration of chloroplasts, homogenates of animal tissue and other biological particles. It is capable of disrupting cell walls while leaving the cell nucleus undisturbed. The French press was invented by Charles Stacy French of the Carnegie Institution of Washington.
The press uses an external hydraulic pump to drive a piston within a larger cylinder that contains the liquid sample. The highly pressurized sample is then squeezed past a needle valve. As the sample passes through the valve, the fluid experiences shear stress and decompression, causing cellular disruption. The major components of a French press are made of stainless steel to prevent sample contamination.
A French press is commonly used to break the resilient plasma membrane and cell walls of bacteria and other microorganisms for isolation of proteins and other cellular components. The disruption of cells in a French press generates 'inside-out' membrane vesicles which are required for many in vitro biochemical assays. The cell is typically chilled overnight before use to preserve enzymatic activities. Disadvantages of the press include that it is not well suited to processing of large sample volumes, and is somewhat awkward to manipulate and clean due to the weight of the assembly (about 30 pounds (14 kg)). Certain types of samples may clog the valve.
Other technologies, such as sonication and ball mills, are available for many of the same purposes, and have their own advantages and disadvantages. For example, sonication can generate high shear forces that break cellular DNA into small fragments. With a French press, the shear force can be carefully modulated by adjusting the piston pressure. The Press provides a single pass through the point of maximum shear force, limiting damage to delicate biological structures due to repeated shear, as occurs in other disruption methods.
Famous quotes containing the words french, pressure, cell and/or press:
“This has been illustrated copiously each day with photographs taken by the author, reproduced by means of cuts such as only French newspaper-engravers can make, presumably etched on pieces of bread.”
—Robert Benchley (1889–1945)
“The mother whose self-image is dependent on her children places on those children the responsibility for her own identity, and her involvement in the details of their lives can put great pressure on the children. A child suffers when everything he or she does is extremely important to a parent; this kind of over-involvement can turn even a small problem into a crisis.”
—Grace Baruch (20th century)
“What Mrs. Thatcher did for women was to demonstrate that if a woman had enough desire she could do what she wanted, do anything a man could do.... Mrs. Thatcher did not have one traditional feminine cell in her body.”
—Julie Burchill (b. 1960)
“If thou be invited of a mighty man, withdraw thyself, and so much the more will he invite thee. Press thou not upon him, lest thou be put back; stand not far off, lest thou be forgotten.”
—Apocrypha. Ecclesiasticus 13:9-10.