Research Interests Evolutionary classification of proteins. Understanding large-scale evolutionary trends in genome evolution. Reconstruction of functional networks of regulatory proteins and metabolic enzyme pathways from genome sequence. Prediction of novel biochemical activities and biological functions of proteins, and inference of organismal biology from comparative sequence and genome analysis. Understanding the fundamental interactions between natural selection and structural/genomic constraints in shaping protein domain diversity. y most important scientific achievements include: Establishment of the deep events in the evolution of topoisomerases and primases, the DNA repair system and diverse DNA binding proteins. Discovery of new domains involved in small molecule binding and elucidation of the evolutionary principles that determine their architectures. The first quantitative estimates of the role of horizontal gene transfer in evolution. Identification of the principal evolutionary events that determined the origin of multicellularity in eukaryotes. Reconstruction of the earliest events that occurred close to the origin of the protein universe. Establishment of the role of lineage specific gene expansions in the emergence of biological diversity. Determination of the principal evolutionary events involved in the emergence of specialized Apicomplexan parasites from a generalized parasitic common ancestor. Elucidating origins of the eukaryotic nonsense mediated RNA degradation system. Elucidating origins of the ubiquitin conjugation system.