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:
“The German intellect wants the French sprightliness, the fine practical understanding of the English, and the American adventure; but it has a certain probity, which never rests in a superficial performance, but asks steadily, To what end? A German public asks for a controlling sincerity.”
—Ralph Waldo Emerson (1803–1882)
“This is a catastrophic universe, always; and subject to sudden reversals, upheavals, changes, cataclysms, with joy never anything but the song of substance under pressure forced into new forms and shapes.”
—Doris Lessing (b. 1919)
“Let man consider what he is in comparison with all existence; let him regard himself as lost in this remote corner of nature; and from the little cell in which he finds himself lodged, I mean the universe, let him estimate at their true value the earth, kingdoms, cities, and himself. What is a man in the infinite?”
—Blaise Pascal (1623–1662)
“Flee from the press and dwell with soothfastness;
Suffice unto thy good though it be small,
For hoard hath hate and climbing ticklishness,
Press hath envy and weal blent overall;”
—Geoffrey Chaucer (1340?–1400)