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Protein Isolation
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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Update: June 2012
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