Calculate the molecular weight of protein sequences including fusion tags and epitope tags.
Paste one or more FASTA sequences (max 200,000,000 characters).
Number of copies of the protein tag to add.
Common protein tags to append to the sequence.
Paste one or more protein sequences in FASTA format (up to 200 million characters). The tool accepts standard amino acid sequences and automatically removes invalid characters.
Select fusion or epitope tags to include in molecular weight calculations. Available tags include FLAG, HA, His6, GST, MBP, SUMO, and many others. This is useful for calculating expected sizes of recombinant proteins.
Click "Execute Tool" to calculate molecular weights. The tool provides average molecular weight (with H2O), molecular weight without water, and extinction coefficient at 280 nm for each sequence.
Review molecular weight values for protein identification, SDS-PAGE predictions, mass spectrometry validation, or protein purification planning. Use extinction coefficients for concentration measurements at 280 nm.
Molecular weight (MW) is the sum of the atomic weights of all atoms in a molecule. For proteins, it is calculated by summing the molecular weights of all amino acid residues plus the weight of a water molecule (H2O) for the protein termini. Typical protein MW ranges from 5 kDa (small peptides) to over 1000 kDa (large complexes).
Epitope tags (FLAG, HA, His6, etc.) and reporter proteins (GFP, GST) are commonly fused to recombinant proteins. You can calculate the molecular weight of the fusion protein by specifying the tag and number of copies.