peptide-qc

Purpose

peptide-qc turns a standard 20-amino-acid sequence into an inspectable, deterministic report:

• residue composition and elemental formula;
• average and monoisotopic molecular mass;
• approximate net charge at a requested pH and approximate pI;
• Kyte–Doolittle hydropathy values and a smoothed profile.

Quick start

cd packages/peptide-qc
npm ci
npm test
npx peptide-qc analyze --sequence ACDEFGHIK --ph 7 --json

The parser accepts whitespace and hyphens as display separators and rejects unsupported or ambiguous residue codes. An explicit unknown modification can be represented as a mass delta, for example --modification phosphorylation=79.966331.

Interpretation boundary

The mass model sums standard residue formulas plus water. Charge and pI use fixed pKa assumptions and are approximations; they do not model solvent, temperature, ionic strength, aggregation, unusual residues, disulfides, cyclization, terminal caps or instrument-specific ion chemistry. Kyte–Doolittle hydropathy is not a solubility or formulation prediction.

This is research-use-only and educational software. It does not identify an unknown, certify a batch, replace a validated analytical method or provide clinical advice. See the package README and CITATION.cff for references and citation guidance.