Amino acid residue masses and A280 extinction contributions

Notes

• Peptide molar mass is the sum of the residue masses plus one water (18.01528 g/mol) for the terminal ends.
• A280 extinction contributions at 280 nm: tryptophan 5500, tyrosine 1490, and 125 per disulfide bond, all in M^-1 cm^-1.
• A protein with no tryptophan or tyrosine barely absorbs at 280 nm, so an A280 reading on one is not a concentration measurement.

Source

Average residue masses, vendor convention. Extinction contributions: Pace et al., Protein Science 1995, 4(11):2411-2423

These values are imported from the same data the Aliquot calculators use, so this page cannot drift away from what the tools compute.

Calculators that use this data

• Protein extinction coefficient (A280): Sequence to ε280, MW, and E0.1%, the Pace way. Feeds the A280 calculator.
• Protein by A280: Protein concentration from absorbance and extinction coefficient.
• Molar mass, grams and moles: Type an element or formula (Sb, NaCl, C6H12O6) and convert grams to moles. Molar mass is computed from cited atomic weights.

Other reference tables

• 1H NMR residual solvent and trace impurity shifts
• Buffer pKa values and temperature coefficients
• GHS hazard statements (H codes)
• GHS precautionary statements (P codes)