What is the difference between the theoretical molecular weight and the observed molecular weight?
The theoretical molecular weight is calculated based on the amino acid sequence of the mature protein. The theoretical molecular weight accounts only for the protein backbone after removal of the signal peptide and any pro-peptides, it does not include any post-translational modifications (PTMs) that may have occurred during the production of the protein. Most PTMs don’t contribute significantly to the molecular weight (MW) of the overall protein. For example, a phosphate group has a MW of 80 Da and acetylation adds 40 Da. The exceptions to this are glycosylation, lipidation, and the addition of ubiquitin. Since all products from Symansis are soluble, lipidation and ubiquitin addition can be ignored. Symansis proteins are expressed out of human cells, facilitating the addition of oligosaccharides (glycans) to the protein backbone. The attachment of glycans to the protein backbone increases the observed molecular weight above the theoretical molecular weight. Most N-linked glycan struct
