A Kyte-Doolittle hydropathy plot averages the standard 20-AA hydrophobicity index across a sliding window to visualize local hydrophobicity along a protein primary sequence. This implementation provides (1) window-size radios 9 / 11 / 19 / 7 plus a custom input (5–21), (2) a GRAVY (Grand Average of Hydropathy) readout, (3) a TM threshold toggle (1.6 default / 1.75 Klein 1985), and (4) automatic TM-domain detection with SVG accent-band overlays.

(1) Locate putative transmembrane (TM) regions (W=19, ≥1.6 or ≥1.75) (2) Probe signal-peptide h-region in the N-terminal 1–30 aa (W=7) (3) Estimate solvent-exposed hydrophilic loops or hydrophobic cores (W=9) (4) Classify soluble vs. membrane proteins from whole-molecule GRAVY (ExPASy ProtParam-compatible)

① Paste protein sequence (1-letter) ② Pick window size: • 9 (surface / exposed loops) • 11 (alpha-helix evaluation) • 19 (TM domain default) • 7 (signal-peptide mode) • Custom 5–21 ③ Toggle TM threshold: 1.6 (default consensus) / 1.75 (Klein 1985 original) ④ Click a Load Example: Bacteriorhodopsin (7TM) or Myoglobin (soluble) ⑤ Output: • GRAVY score (whole-molecule average) • Hydropathy curve (self-drawn SVG) • Threshold horizontal guide • TM candidate regions as accent bands plus start/end/avgScore cards

Example 1) Bacteriorhodopsin (W=19, threshold 1.6) → 7 distinct hydropathy peaks detected → matches the 7 transmembrane alpha-helices of the BR family Example 2) Myoglobin (W=19, threshold 1.6) → 0 regions above threshold → soluble globular protein Example 3) Signal-peptide mode (W=7, N-term 1–30) → auto-marks h-region candidates of secreted / targeting proteins