Department of Biochemistry, University College, Cork, Ireland and EMBL-European Bioinformatics Institute, Hinxton, Cambridge CB10 1RQ, UK. emmet@chah.ucc.ie|Department of Biochemistry, University College, Cork, Ireland and EMBL-European Bioinformatics Institute, Hinxton, Cambridge CB10 1RQ, UK. emmet@chah.ucc.ie|Department of Biochemistry, University College, Cork, Ireland and EMBL-European Bioinformatics Institute, Hinxton, Cambridge CB10 1RQ, UK. emmet@chah.ucc.ie