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Name: Ali
Status: student
Grade: 9-12
Location: AL
Country: USA
Date: N/A 


Question:
How do scientists isolate and identify the proteins produced by a particular type of cell?



Replies:
Hi Ali,

Scientists over the years have used a variety of methods to isolate and identify the proteins made by a cell. One of the key advancements in protein biochemistry was the development of a simple way of separating proteins out by size, using a method known as "gel electrophoresis". Put simply, proteins are "loaded" onto a gel and a voltage is applied across the gel in a buffer in which proteins are coated with negatively charged molecules. Proteins will then travel towards the positive end of the gel, and the distance that they travel across the gel will be determined by how large they are. This method therefore allows for the separation of proteins out based on their mass.

Once the proteins are separated out, they can be excised from the gel and sequenced by a chemical method known as Edman degradation, or by a more modern method known as "mass spectrometry", in which the protein is broken down into small pieces whose masses are very precisely measured with a mass spectrometer.

In addition, scientists often fractionate cells by breaking them apart and separating out their components based on properties such as density or solubility. The scientist can then deduce which proteins are found in which parts of the cell, which is an important step to understanding their function.

Ethan Greenbalt


Ali,

There are a lot of different techniques used, depending on which proteins, how much protein, and how much sensitivity you need. Gel electrophoresis is a common and widely used technique. A more complex, but more sensitive, technique is known as mass spectrometry. Finally, chromatography is one of the more common industrial (large scale) methods to separate proteins. All three involve various types of extractions, chemical treatments, or other preparation methods. All three methods are described in detail on the web -- and of course feel free to contact AAS if you have specific questions.

Hope this helps,
Burr



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