One of the major challenges of modern medicine is to understand how the human organism defends itself against invasions and diseases. The biggest mystery is the human immune system, and understanding this ultimately requires knowledge of the sequence repertoire of human antibodies and their respective antigens. The purpose of the TopSpec project is to be the first in the world to solve this challenge, opening up opportunities in medical research and drug development that are today only dreamt about. We will create a breakthrough technology that will revolutionize academic, clinical and industrial proteomics and dramatically advance the development of new generation antibody- and protein-based therapeutics. Antibodies represent the most sophisticated line of natural defense against disease. Knowing exactly which antibodies are produced in response to a particular disease enables us not only to better understand the cause of the disease but also to provide new-generation cures in the form of personalized therapeutic antibodies. The limiting factor for this to truly be achieved is to find a way to analyze and sequence large molecules in the gas phase, and this represents a formidable challenge. The TopSpec project will develop ground-breaking TOP-down tandem mass SPECtrometry (MS/MS) approaches based on novel radical gas-phase ion-electron and ion-atom reactions, and implement them on a unique, hyphenated, ultrahigh-resolution MS platform. Another “killer innovation” is the ability to greatly simplify MS/MS spectra of large molecules by adding another dimension of separation – collisional cross-sections of fragment ions using two parallel approaches. TopSpec will be the first project to implement de-convolution of massively overlapping isotopic clusters, solving one of the greatest challenges in top-down MS of large molecules.