Molecule Tutorials - Herong's Tutorial Examples - v1.26, by Herong Yang
Alpha Helix and Beta Sheet
This section provides a quick introduction of protein secondary structures, alpha helix and beta sheet. Both structures are stabilized by hydrogen bonds between oxygen atoms and hydrogen atoms of two amino acid residues lined up side by side.
What Is Alpha Helix? - An alpha helix is a secondary structure in a protein, where a section of the protein sequence is twisted into a coil conformation. The oxygen of the carboxylic acid group of an amino acid residue is lined up to the hydrogen of the amino group of another amino acid residue located one circle away on the coil conformation to form a hydrogen bond.
Those hydrogen bonds keep an alpha helix stabilized.
The picture below provides a good illustration of an alph helix (source: researchgate.net):
What Is Beta Sheet? - A beta sheet is a secondary structure in a protein, where a section of the protein sequence is positioned side by side with another section of the protein sequence into a pleated sheet conformation. The oxygen of the carboxylic acid group of an amino acid residue is lined up to the hydrogen of the amino group of another amino acid residue from the adjacent section on the pleated sheet conformation to form a hydrogen bond.
Those hydrogen bonds keep a beta sheet stabilized.
The picture below provides a good illustration of a beta sheet formed with 3 sections of the protein sequence (source: researchgate.net):
If two adjacent sections of the protein sequence in a beta sheet are running in the same direction from N-terminal to C-Terminal, they have a parallel beta sheet relation. For example, the top two sections of the protein sequence in the above picture have a parallel beta sheet relation.
If two adjacent sections of the protein sequence in a beta sheet are running in different directions from N-terminal to C-Terminal, they have an anti-parallel beta sheet relation. For example, the bottom two sections of the protein sequence in the above picture have an anti-parallel beta sheet relation.
Table of Contents
Molecule Names and Identifications
Peptide, Peptide Bond, Amino Acid Residues
Protein Visualization - Ribbon Diagram
Composed Proteins or Protein Complexes
wwpdb.org - Worldwide PDB (Protein Data Bank)
Nucleobase, Nucleoside, Nucleotide, DNA and RNA
ChEMBL Database - European Molecular Biology Laboratory
PubChem Database - National Library of Medicine
INSDC (International Nucleotide Sequence Database Collaboration)
HGNC (HUGO Gene Nomenclature Committee)