Hydrophobicity

Hydrophobicity computes quantitative hydropathy profiles along protein sequences to identify hydrophilic and hydrophobic regions from amino acid composition for structural interpretation.

Key Features:

• Hydropathy scale: Assigns a hydrophobicity value to each of the 20 amino acid side chains based on aggregated experimental measurements.
• Sliding-window averaging: Uses a moving-window (sliding segment) approach to compute average hydropathy values over fixed-length segments from the N-terminus to the C-terminus.
• Positional hydropathy profile: Generates a continuous profile of positional hydropathy scores along the sequence.
• Reference midpoint: Plots the trace alongside a reference midpoint line representing the grand average hydropathy observed across typical protein compositions.
• Region classification: Identifies sequence segments with consecutive scores above the midpoint as hydrophobic and those below as hydrophilic.
• Structural correlation: Predicted hydrophobic stretches correlate with buried core regions in soluble, globular proteins.
• Transmembrane delineation: Predicted hydrophobic stretches delineate transmembrane segments within lipid bilayers and support identification of membrane-spanning helices.
• Automated scoring: Performs automated computation of positional hydropathy scores.
• Visualization: Produces a plotted hydropathy trace for positional interpretation.

Scientific Applications:

• Structural inference: Infers aspects of protein structural organization directly from primary sequence hydropathy patterns.
• Transmembrane prediction: Predicts and delineates transmembrane segments and putative membrane-spanning helices within lipid bilayers.
• Core residue identification: Aids identification of buried core regions in soluble, globular proteins relevant to folding and solubility assessments.
• Sequence annotation and exploration: Supports annotation of protein sequences for hydrophobicity features and exploratory analysis.

Methodology:

Applies an empirically derived hydropathy scale assigning values to the 20 amino acids from aggregated experimental measurements, computes moving-window average hydropathy over fixed-length segments from N- to C-terminus to produce a continuous positional profile, plots the trace with a grand-average midpoint reference, and classifies segments above or below the midpoint as hydrophobic or hydrophilic.