Cell disruption by nitrogen decompression

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Cell disruption by rapid decompression has been used for many years by investigators who wanted to overcome the limitations imposed by other cell disruption procedures. Although the technique is not new, interest in the decompression method and many new applications for it have grown rapidly in recent years following the introduction of new pressure equipment.

1 Cell disruption By Nitrogen Decompression
2 Applications
3 How It Works
4 Reasons for Effectiveness
5 See also
6 External links

[edit] Cell disruption By Nitrogen Decompression

An effective and rapid way to:

Homogenize cells and tissues
Release intact organelles
Prepare cell membranes
Release labile biochemicals
Produce uniform and repeatable homogenates without subjecting the sample to extreme chemical or physical stress.

[edit] Applications

The nitrogen decompression method is particularly well suited for treating mammalian and other membrane bound cells. It has also been used successfully for treating plant cells, for releasing virus from fertilized eggs and for treating fragile bacteria. It is not recommended for untreated bacterial cells, but this restriction can be eliminated by using various pretreatment procedures to weaken the cell wall. Yeast, fungus, spores and other materials with tough walls do not respond well to this method.

[edit] How It Works

The principle of the method is quite simple. Large quantities of nitrogen are first dissolved in the cell under high pressure within a suitable pressure vessel. Then, when the gas pressure is suddenly released, the nitrogen comes out of the solution as expanding bubbles that stretch the membranes of each cell until they rupture and release the contents of the cell.

[edit] Reasons for Effectiveness

Nitrogen decompression is a gentle method. Although sometimes referred to as explosive decompression, nitrogen decompression is actually a gentle method for homogenizing or fractionating cells since the chemical and physical stresses that it imposes upon the sub-cellular components are held to an absolute minimum. It is much more protective of delicate enzymes and organelles than ultrasonic and mechanical homogenizing methods. In fact, it compares favorably to the controlled disruptive action obtained in a PTFE and glass mortar and pestle homogenizer, but it does the job faster and more uniformly, with the added ability to treat large samples quickly and conveniently.

There is no heat damage. While other disruptive methods depend upon friction or a mechanical shearing action that generates heat, the nitrogen decompression procedure is accompanied by an adiabatic expansion that cools the sample instead of heating it.

In addition, the entire cycle can be conducted at low temperature by pre-chilling or by operating the bomb in an ice bath. The bomb can also be filled with ice to keep the sample cool during the processing period.

There is no oxidation. The blanket of inert nitrogen gas that saturates the cell suspension and the homogenate offers excellent protection against oxidation of any labile cell components. Although other gases: carbon dioxide, nitrous oxide, carbon monoxide and compressed air have been used in this technique, nitrogen is preferred because of its non-reactive nature and because it does not alter the pH of the suspending medium. In addition, nitrogen is preferred because it is generally available at low cost and at pressures suitable for this procedure.

Any suspending medium can be used. The suspending medium can be chosen for its comparability with the end use of the homogenate and without regard for its adaptability to the disruptive process. This offers great flexibility in the preparation of cell suspensions and produces a clean homogenate that will not require intermediate treatment to remove contaminates which might be introduced when using other disruption methods.

Each cell is exposed only once. Once released, subcellular substances are not exposed to continued attrition that might denature the sample or produce unwanted damage. There is no need to watch for a peak between enzyme activity and percent disruption.

The product is uniform. Since nitrogen bubbles are generated within each cell, the same disruptive force is applied uniformly throughout the sample, thus ensuring unusual uniformity in the product. Cell-free homogenates can be produced.