EMBOSS HMOMENT: Hydrophobic Moment

Description: hmoment plots out the hydrophobic moment. The hydrophic moment is the hydrophobicity of a peptide measured for a specified angle of rotation per residue. Periodicities in the polar/apolar character of the amino acid sequence of a protein can be examined by assigning to each residue a numerical hydrophobicity and searching for periodicity in the resulting one-dimensional function. The strength of each periodic component is the quantity that has been termed the hydrophobic moment.

When proteins of known three-dimensional structure are examined, it is found that sequences that form alpha helices tend to have, on average, a strong periodicity in the hydrophobicity of about 3.6 residues, the period of the alpha helix. The angle of rotation per residue in alpha helices is 100 degrees. Similarly, many sequences that form strands of beta sheets tend to have a periodicity in their hydrophobicity of about 2.3 residues, the period typical of beta structure. The angle of rotation per residue in beta sheets is 160 degrees. This means that many protein sequences tend to form the periodic structure that maximizes their amphiphilicity.

The hydrophobic moment is measured within a sliding window using the method of Eisenberg et al. The default angle of 100 degrees is used for the alpha-helix results and the default of 160 degrees is used for the beta-sheet results. These angles can be changed if required using the appropriate options.

Alpha Helix Angle: Beta Sheet Angle: Baseline:
Window: Plot:

Please enter the protein sequence with FASTA format you want to analyze:

If you have any questions please e-mail: Milton Saier - msaier@ucsd.edu