Systems for identifying proteoforms of tau protein

A system for identifying proteoforms of Tau protein, comprising:

• one or more solid supports comprising molecules of Tau protein immobilized thereon, wherein individual molecules of immobilized Tau protein are individually addressable;
• a source of a library of a plurality of different affinity reagents, each different affinity reagent having a binding affinity to a Tau protein having a different modification;
• a fluidic system for delivering the plurality of different affinity reagents to the one or more solid supports to contact the affinity reagents with the individual molecules of the Tau protein;
• a detector for detecting whether each of the different affinity reagents binds to individual molecules of the Tau protein;
• and
• a processor programmed to identify a plurality of proteoforms of the Tau protein present on the one or more solid supports by identifying proteoforms of the Tau protein represented by each of the plurality of individual molecules of Tau protein based upon identification of a presence or absence of at least 3 different modifications within each of the individual molecules of the Tau protein.