Our research focuses on the evolution and variability of proteins and their function. We examine the relationship between protein sequence, structure and function with a focus on various aspects such as the functional variability of enzyme families. Additionally, we try to predict the effect of non-synonymous (amino acid changing) mutations on the function of a protein: we developed in close cooperation with various groups a tool called "PolyPhen" (Polymorphism Phenotyping) that enables researchers to evaluate the phenotypic effect of mutations. Besides our own research we support and closely cooperate with the other groups of the department. This support includes general tasks such as the analysis of biological data sets, prediction of the function of proteins, or the prediction of protein domains in candidate genes for functional assays and crystallography. This close interaction helps us to develop new bioinformatic tools and to improve and verify our theoretical approach.