French pressure cell press
The French pressure cell press, or French press, is an apparatus used in biological experimentation to disrupt
Cell disruption
Cell disruption is a method or process for releasing biological molecules from inside a cell.- Choice of disruption method:The production of biologically-interesting molecules using cloning and culturing methods allows the study and manufacture of relevant molecules.Except for excreted molecules,...

 the plasma membrane of cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s 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
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...

 within a larger cylinder that contains the liquid sample. The highly pressurized sample is then squeezed past a needle valve
Needle valve
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.- Construction and operation :...

. As the sample passes through the valve, the fluid experiences shear stress
Shear stress
A shear stress, denoted \tau\, , is defined as the component of stress coplanar with a material cross section. Shear stress arises from the force vector component parallel to the cross section...

 and decompression
Decompression has several meanings:* Decompression , the release of pressure and the opposition of physical compression* Decompression sickness, a condition arising from the precipitation of dissolved gases into bubbles inside the body on depressurization* Decompression , a procedure used to treat...

, 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 wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

s of bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 and other microorganisms for isolation of protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s 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 (13.6 kg)). Certain types of samples may clog the valve.

Other technologies, such as sonication
thumb|right|A sonicator at the [[Weizmann Institute of Science]] during sonicationSonication is the act of applying sound energy to agitate particles in a sample, for various purposes. In the laboratory, it is usually applied using an ultrasonic bath or an ultrasonic probe, colloquially known as...

 and ball mill
Ball mill
A ball mill is a type of grinder used to grind materials into extremely fine powder for use in mineral dressing processes, paints, pyrotechnics, and ceramics.-Description:...

s, 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.

External links

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