GRAVY
Calculate GRAVY (Grand Average of Hydropathy). Positive = hydrophobic, negative = hydrophilic.
Calculate GRAVY (Grand Average of Hydropathy). Positive = hydrophobic, negative = hydrophilic.
Calculate the aliphatic index of protein sequences. A measure of the relative volume occupied by aliphatic side chains, indicating thermostability.
Calculate the molar extinction coefficient of protein sequences at 280 nm. Used for protein concentration determination by UV spectroscopy.
Find potential N-linked glycosylation sites (NX[S/T] sequons) in protein sequences. Identifies asparagine residues in the consensus motif for N-glycosylation.
Calculate the instability index of protein sequences. Values above 40 indicate an unstable protein with a short half-life in vitro.
Calculate the molecular weight (MW) of protein sequences in Daltons. Supports FASTA format input and batch processing.
Calculate the theoretical isoelectric point (pI) of protein sequences. The pI is the pH at which a protein carries no net electrical charge.
Analyze amino acid composition of protein sequences. The tool accepts FASTA sequences and outputs the percentage of each amino acid in the sequence.
Scan protein sequences for biologically important motifs including glycosylation sites, phosphorylation sites, nuclear localization signals, prenylation motifs, and more.
Faithful static-mode Aggrescan3D wrapper for per-residue aggregation propensity analysis from a single protein structure.
Plot net charge vs pH for protein sequences. Visualize how protein charge changes across pH 0-14 and identify the isoelectric point (pI) where the net charge crosses zero.
GRAVY (Grand Average of Hydropathy) is a fundamental metric for quantifying the overall hydrophobicity or hydrophilicity of a protein sequence.
Introduced by Jack Kyte and Russell Doolittle in their seminal 1982 paper, this index has become one of the most widely used protein parameters in protein science.
The GRAVY score provides rapid insight into a protein's solubility, membrane association, and folding behavior. A positive value indicates a hydrophobic protein, while a negative value indicates a hydrophilic protein.
GRAVY is calculated by summing the hydropathy values of all amino acids in a sequence and dividing by the sequence length:
Where is the total number of amino acids and is the hydropathy value of amino acid . This simple arithmetic mean yields a single value that characterizes the entire protein's hydropathic character.
The calculation uses experimentally derived hydropathy values for each amino acid. These values, ranging from +4.5 (most hydrophobic) to -4.5 (most hydrophilic), were determined by combining water-vapor transfer free energies with solvent accessibility data from crystal structures.
| Amino Acid | Value | Amino Acid | Value |
|---|---|---|---|
| Ile (I) | 4.5 | Gly (G) | -0.4 |
| Val (V) | 4.2 | Ser (S) | -0.8 |
| Leu (L) | 3.8 | Trp (W) | -0.9 |
| Phe (F) | 2.8 | Tyr (Y) | -1.3 |
| Cys (C) | 2.5 | Pro (P) | -1.6 |
| Met (M) | 1.9 | His (H) | -3.2 |
| Ala (A) | 1.8 | Glu (E) | -3.5 |
| Thr (T) | -0.7 | Gln (Q) | -3.5 |
The GRAVY score directly correlates with protein solubility and membrane interaction potential:
Most soluble proteins have negative GRAVY scores. Transmembrane proteins and membrane-associated domains typically show positive values due to their enrichment in hydrophobic residues.
| Asn (N) |
| -3.5 |
| Asp (D) |
| -3.5 |
| Lys (K) | -3.9 | Arg (R) | -4.5 |