Protein Aromaticity

Calculate aromatic F/W/Y residue fraction of a protein sequence.

Description

Aromaticity measures the fraction of phenylalanine, tryptophan and tyrosine residues.

Aromaticity measures the fraction of phenylalanine, tryptophan and tyrosine residues. It is a composition summary rather than an absorbance calculation.^[1]

Calculate aromatic F/W/Y residue fraction of a protein sequence.

When to use Protein Aromaticity

Use this tool to calculate aromatic F/W/Y residue fraction of a protein sequence.

Prepare the canonical sequence, peptide assignments, fitted assay parameters or upstream measurements requested. Keep corresponding entries aligned, use the stated mass and signal units, and remove FASTA headers before entering sequence text.

How to use Protein Aromaticity and understand its results

Prepare the canonical sequence, peptide assignments, fitted assay parameters or upstream measurements requested. Keep corresponding entries aligned, use the stated mass and signal units, and remove FASTA headers before entering sequence text.
Enter sequence using the field table and calculation rules, then run the tool.
Read aromaticResidues, aromaticFraction. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
sequence	Sequence	string	Required

Enter a canonical sequence. Return aromatic count and fraction in 0–1. Histidine is not included in this tool’s aromatic set.

The shared sequence helper trims outer whitespace and uppercases the sequence. It requires at least one residue from ACDEFGHIKLMNPQRSTVWY. Internal whitespace, FASTA headers, ambiguous letters and modified-residue notation are rejected. Sequence indexes refer to the normalized sequence; individual tools may preserve original strings in their returned lists as explained above.

aromaticFraction=(Fcount+Wcount+Ycount)/sequenceLength

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
aromaticResidues	Aromatic residues	number
aromaticFraction	Aromatic fraction	number

json

{
  "input": {
    "sequence": "FWYA"
  },
  "output": {
    "aromaticResidues": 3,
    "aromaticFraction": 0.75
  }
}

Limitations and assumptions

The fraction does not account for structure, chromophores or differing residue extinction coefficients.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Protein Extinction 280: Estimate 280-nm molar extinction coefficient from Trp, Tyr, and cystine. For a complementary task, use Amino Acid Composition: Tabulate amino-acid counts and composition percentages.

References

Protein Aromaticity — tool.io

Similar or alternative tools

Protein Extinction 280
Estimate 280-nm molar extinction coefficient from Trp, Tyr, and cystine.
Amino Acid Composition
Tabulate amino-acid counts and composition percentages.