Peptide: Difference between revisions
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<applet load="pepb27_4.pdb" size="300" color="white" frame="true" caption="Peptides are small chains of amino acids." align="right" /> | <applet load="pepb27_4.pdb" size="300" color="white" frame="true" caption="Peptides are small chains of amino acids." align="right" /> | ||
Peptides are chains of amino acids linked by peptide bonds. Long peptides, or polypeptides, are called proteins. | |||
==Peptides & Backbones== | |||
This is the backbone of 1 amino acid. Adding to the backbone with an additional amino acid on each side gives a tripeptide (3 amino acids). No side groups are shown, and most hydrogens are omitted. Now each amino acid has a 1 carbon side group so we have Ala-Ala-Ala (tri-alanine). Adding a carbon chain plus an NH3 on the first amino acid gives Lys-Ala-Ala. Adding three more carbons to the 3rd amino acid gives [[isoleucine]]: Lys-Ala-Ile. The 4th amino acid is threonine with its hydroxyl, giving Lys-Ala-Ile-Thr. Here is the shape of the tetrapeptide (4 AAs). The stick representation has too much detail for larger proteins, so the α-carbons are connected with a line called the backbone trace. Showing only the backbone makes it easier to see the path of the protein chain (its secondary and tertiary structure). | |||
