Amino Acid Chart

All 20 standard amino acids with one- and three-letter codes, molecular weight, side-chain pKa, pI, Kyte–Doolittle hydropathy, class, polarity, charge, essentiality and codons — sortable, searchable and exportable.

The Amino Acid Chart is a sortable reference table of the 20 proteinogenic amino acids: name, 3-letter and 1-letter codes, molecular weight (free amino acid), side-chain pKa, isoelectric point, Kyte–Doolittle hydropathy index, side-chain class, polarity, net charge at pH 7, whether it is essential in humans, and its codons.

Free, runs in your browser. Nothing you enter is uploaded.

How to use it

1. Search or filter.
2. Click a column header to sort.
3. Copy as CSV for your notes.

What you enter

• None (reference)

What you get

• Codes, MW, pKa, pI, hydropathy, class, charge, codons

Formula

Residue mass in a peptide = free amino acid MW − 18.015 (H₂O lost on peptide-bond formation).

pKa values are for the ionisable side chains; pI is the pH at which the free amino acid carries no net charge. Hydropathy > 0 is hydrophobic.

Worked example

Input: Filter: charged

Result: Arg, Lys, His (positive); Asp, Glu (negative)

Five amino acids carry a side-chain charge at physiological pH.

Questions

Which amino acids are essential?

Nine for adult humans: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine.

Which amino acids are hydrophobic?

By Kyte–Doolittle: Ile, Val, Leu, Phe, Cys, Met and Ala have positive hydropathy.

What are the one-letter codes?

A Ala, R Arg, N Asn, D Asp, C Cys, Q Gln, E Glu, G Gly, H His, I Ile, L Leu, K Lys, M Met, F Phe, P Pro, S Ser, T Thr, W Trp, Y Tyr, V Val.

Limitations

• Values are textbook standards (Lehninger); pKa in a folded protein can shift by several units.

References

• Kyte J, Doolittle RF (1982). A simple method for displaying the hydropathic character of a protein. J Mol Biol 157:105-132.

Related reading

• Amino Acid Structure
• Amino Acid Sequence
• Protein Monomers, Amino Acids, and Peptide Synthesis
• Isoelectric Focusing (IEF) for Protein Analysis

More Molecular Biology

• Codon Table (Interactive Genetic Code)
• qPCR Efficiency & Standard Curve Calculator (Copy Number)
• ΔΔCt Calculator: qPCR Fold Change and Relative Expression
• Ligation Insert-to-Vector Mass Calculator
• Transformation Efficiency Calculator

All free tools · By Dr. Zubair Khalid, DVM, MS, PhD.