5: Determine the Amino Acid Sequence
|First, the proteins
have to be "digested" into their amino acid pieces. Then
chemical reactions can determine what amino acids are present.
This used to be a time-consuming and laborious process. Nowadays,
laboratory instruments perform this function automatically, identifying not only
what amino acids are present but also their sequence (order.)
|The diagram on the right shows
how atoms in an amino acid are arranged. Carbon atoms are
represented by the letter C, oxygen atoms by O, Nitrogen
by N, and hydrogen by H. The R stands for the rest of the
molecule which is different for each kind of amino acid.
The instruments use a
chemical reaction that strips off one amino acid at a time, starting
at the end with a Nitrogen group. By lopping off one amino acid at
one end, the next amino acid has an exposed Nitrogen group, and it
in turn can be lopped off and identified.