Rui Vitorino has been involved in the characterization of saliva using proteomics tools. Saliva is a complex biological fluid enriched in glycoproteins and small peptides. As a first approach, salivary proteins were resolved by two-dimensional gel electrophoresis yielding the publication of one of the first 2DE maps. Following the main goal of this project, salivary peptides were characterized by LC-MS addressing in few identifications. Later, face to the wide range of different peptides, other approaches were developed which allowed the identification of more than 2000 endogenous peptides in saliva. Nowadays, most of his research has been dedicated to pathologies including dental caries, diabetes and head and neck cancer. Although his research is addressed to saliva, in the latest years, he has participated in several projects aiming to develop methodologies or find clues through proteome analysis. Among the methodological works: a) organelles fractionation; b) PTM characterization by mass spectrometry; c) protein complex characterization; d) glycoprotein characterization through nanoparticle-lectin immobilized systems.