Fig 1: Application of Iterative Mapping to measure proteoforms of tau.a, Tau contains a series of splice variants: N1 and N2 tau isoforms (orange and dark navy blue, respectively), as well as 3R and 4R isoforms (light blue), and PTMs. The six dominant splice variants have different molecular weights (MW). Approximate epitope positions for monoclonal antibodies (mAB) used for enrichment or for isoform and PTM site-specific detection are shown. b, Primary imaging data capturing a representative area of 130 µm × 130 µm of flow cell surface showing ~16,000 landing pads. Each illuminated pixel is a single tau–nanoparticle conjugate. Green halos indicate a positive binding event. ‘Proteoform 2’ shows binding with antibodies targeting 0N, pT181 and pS396, leading to an identification as the 0N-3R (pT181, pS396) proteoform group. c, Tau proteoforms standards (0N3R, 2N4R-PKA and 0N4R-ERK) and expected epitope combinations (A–J). Right: the relative abundance of individual proteoforms in cpm. Left: the epitope profile of mixtures of tau proteoforms resolved by Iterative Mapping of proteoforms. Error bars represent standard deviation of the mean, and each sample has three technical replicates.
Fig 2: Proteoforms vs Proteoform Groups.Each individual molecular form of a protein that arises through combinations of genetic variation, alternative splicing and post-translational modifications has been denoted to be a proteoform. The exact chemical formula for a proteoform can be elaborated. Proteoform groups, on the other hand, are a collection of proteoforms that contain a common shared set of observed alterations. For example, a proteoform group may be defined as all the forms of Tau that contain phosphorylation at both positions 217 and 231.
Supplier Page from BioLegend for Recombinant Human Tau-383 (0N4R)