Ribozymes and RNA catalysis : introduction and primer -- Proton transfer in ribozyme catalysis -- Finding the Hammerhead ribozyme active site -- Hammerhead ribozyme crystal structures and catalysis -- The Hairpin and Varkud satellite ribozymes -- Catalytic mechanism of the HDV ribozyme -- Mammalian self-cleaving ribozymes -- The structure and action of glmS ribozymes -- A structural analysis of Ribonuclease P -- Group I introns : biochemical and crystallographic characterization of the active site structure -- Group II introns : catalysts for splicing, genomic change and evolution -- The GIR1 branching ribozyme -- Is the spliceosome a ribozyme? -- Peptidyl transferase mechanism : the ribosome as a ribozyme -- Folding mechanisms of Group I ribozymes.