Bioinformatics Research Centre, Department of Computer Science, University of Glasgow, Glasgow G12 8QQ, UK.|Bioinformatics Research Centre, Department of Computer Science, University of Glasgow, Glasgow G12 8QQ, UK.|Bioinformatics Research Centre, Department of Computer Science, University of Glasgow, Glasgow G12 8QQ, UK.|Bioinformatics Research Centre, Department of Computer Science, University of Glasgow, Glasgow G12 8QQ, UK.