Primary and secondary protein structure
The primary structure of a protein is the sequence of the amino acids.
A shorthand way of representing primary structure uses three letter abbreviations for amino acids.
The secondary structure is the way in which the peptide chain is folded or coiled in the protein.
The folding and coiling of the peptide chain is due to the attractive forces known as hydrogen bonds between NH and CO groups in the same peptide backbone.
Two important secondary structures are α helices and β pleated sheets.
In β pleated sheets the nitrogen and the two carbons lie in the same plane. The pleat is due to the fact that the geometry of bonds above CH is different to the geometry of bonds about C=O or NH.
A shorthand way of representing primary structure uses three letter abbreviations for amino acids.
A protein containing alanine, serine and leucine in a portion of its chain would have that portion of the chain represented by Ala-Ser-Leu.
The secondary structure is the way in which the peptide chain is folded or coiled in the protein.
The folding and coiling of the peptide chain is due to the attractive forces known as hydrogen bonds between NH and CO groups in the same peptide backbone.
This attraction is due to the H bonded to N being slightly positive and the O bonded to C being slightly negative.
Two important secondary structures are α helices and β pleated sheets.
| In the α helix structure: the hydrogen bonds are between amino acids in the same chain (usually 5 or 6 amino acid residues apart) . |  |
| In β pleated sheets: the hydrogen bonds are between amino acids in parts of the same chain that lie parallel to one another. |  |
In β pleated sheets the nitrogen and the two carbons lie in the same plane. The pleat is due to the fact that the geometry of bonds above CH is different to the geometry of bonds about C=O or NH.