Peptide: Difference between revisions
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Eric Martz (talk | contribs) tightened up introductory section, and added link to Wikipedia |
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<applet load="pepb27_4.pdb" size="500" color="white" frame="true" caption="Peptides, small chains of amino acids." align="right" /> | <applet load="pepb27_4.pdb" size="500" color="white" frame="true" caption="Peptides, small chains of amino acids." align="right" /> | ||
Peptides are chains of amino acids linked by peptide bonds. | Peptides are short chains of amino acids linked by peptide bonds. A '''peptide''' is not more than 30-50 amino acids in length. Longer chains of amino acids are called polypeptides or proteins. Wikipedia offers a good discussion of [http://en.wikipedia.org/wiki/Peptide peptides, with examples]. | ||
==Peptides & Backbones== | ==Peptides & Backbones== | ||
This is the '''<scene name='Peptide/Emartz_view1/6'>backbone</scene>''' of 1 amino acid. Adding to the backbone with an additional amino acid on each side gives a '''<scene name='Peptide/Emartz_view2/6'>tripeptide</scene>''' (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 '''<scene name='Peptide/Emartz_view3/4'>Ala-Ala-Ala</scene>''' (tri-alanine). Adding a carbon chain plus an NH3 on the first amino acid gives '''<scene name='Peptide/Emartz_view4/5'>Lys-Ala-Ala</scene>'''. Adding '''<scene name='Peptide/Emartz_view5/4'> three more carbons </scene>''' to the 3rd amino acid gives isoleucine: Lys-Ala-Ile. The 4th amino acid is threonine with its hydroxyl, giving '''<scene name='Peptide/Emartz_view6/2'> Lys-Ala-Ile-Thr</scene>'''. Here is the shape of the '''<scene name='Peptide/Emartz_view7/2'>tetrapeptide</scene>''' (4 AAs). The stick representation has too much detail for larger proteins, so the α-carbons are connected with a line called the '''<scene name='Peptide/Emartz_view8/3'>backbone trace</scene>'''. Showing only the '''<scene name='Peptide/Emartz_view9/5'>backbone</scene>''' makes it easier to see the path of the protein chain (its secondary and tertiary structure). | This is the '''<scene name='Peptide/Emartz_view1/6'>backbone</scene>''' of 1 amino acid. Adding to the backbone with an additional amino acid on each side gives a '''<scene name='Peptide/Emartz_view2/6'>tripeptide</scene>''' (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 '''<scene name='Peptide/Emartz_view3/4'>Ala-Ala-Ala</scene>''' (tri-alanine). Adding a carbon chain plus an NH3 on the first amino acid gives '''<scene name='Peptide/Emartz_view4/5'>Lys-Ala-Ala</scene>'''. Adding '''<scene name='Peptide/Emartz_view5/4'> three more carbons </scene>''' to the 3rd amino acid gives isoleucine: Lys-Ala-Ile. The 4th amino acid is threonine with its hydroxyl, giving '''<scene name='Peptide/Emartz_view6/2'> Lys-Ala-Ile-Thr</scene>'''. Here is the shape of the '''<scene name='Peptide/Emartz_view7/2'>tetrapeptide</scene>''' (4 AAs). The stick representation has too much detail for larger proteins, so the α-carbons are connected with a line called the '''<scene name='Peptide/Emartz_view8/3'>backbone trace</scene>'''. Showing only the '''<scene name='Peptide/Emartz_view9/5'>backbone</scene>''' makes it easier to see the path of the protein chain (its secondary and tertiary structure). | ||
Revision as of 22:49, 3 November 2008
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Peptides are short chains of amino acids linked by peptide bonds. A peptide is not more than 30-50 amino acids in length. Longer chains of amino acids are called polypeptides or proteins. Wikipedia offers a good discussion of peptides, with examples.
Peptides & BackbonesPeptides & Backbones
This is the of 1 amino acid. Adding to the backbone with an additional amino acid on each side gives a (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 (tri-alanine). Adding a carbon chain plus an NH3 on the first amino acid gives . Adding to the 3rd amino acid gives isoleucine: Lys-Ala-Ile. The 4th amino acid is threonine with its hydroxyl, giving . Here is the shape of the (4 AAs). The stick representation has too much detail for larger proteins, so the α-carbons are connected with a line called the . Showing only the makes it easier to see the path of the protein chain (its secondary and tertiary structure).