ProtParam

ProtParam accepts one UniProtKB identifier or a raw single-letter protein sequence; spaces and numbers in raw input are ignored. Identifier input offers annotated chains/domains or start/end positions, with the whole sequence used when both boxes are empty. Results include molecular weight, theoretical pI, composition and derived indices. Post-translational modifications cannot be specified, and multimeric state is not inferred. The documentation's 280 nm extinction estimate gives separate fully oxidized/reduced-cysteine assumptions for proteins in water and warns of larger errors without tryptophan or with other absorbing chromophores. Its half-life estimate follows the N-terminal-residue rule for human, yeast and E. coli models. These are sequence-based predictions with stated model assumptions.