Amino Acid Calculator

This calculator analyzes peptide and protein sequences to determine molecular weight, isoelectric point, net charge, extinction coefficient, and amino acid composition. It's useful for protein characterization, purification planning, and biochemical analysis.

Molecular weight is calculated by summing the atomic weights of all atoms in the peptide sequence, accounting for peptide bond formation (loss of water molecules). Standard amino acid residue weights are used for each amino acid in the sequence.

The isoelectric point (pI) is the pH at which the peptide has no net charge. It's calculated by analyzing the ionizable groups (amino, carboxyl, and side chain groups) and determining the pH where positive and negative charges balance.

Net charge is calculated using the Henderson-Hasselbalch equation for each ionizable group in the peptide. The charges of all groups are summed to give the overall net charge at the specified pH value.

GRAVY (Grand Average of Hydropathy) is the average hydropathy value of all amino acids in the sequence. Positive values indicate hydrophobic proteins, while negative values indicate hydrophilic proteins.

Extinction coefficients are calculated based on the content of tryptophan, tyrosine, and cysteine residues using established formulas. The values are theoretical estimates and may vary slightly from experimental values due to protein folding effects.

Yes, the calculator accepts both standard one-letter amino acid codes (like A, R, N) and three-letter codes (like Ala, Arg, Asn). Mixed formats in the same sequence are also supported.

Calculated properties assume the peptide is in its linear form and don't account for secondary structure, disulfide bonds, or post-translational modifications. Temperature and ionic strength can also affect actual vs theoretical values.