Computer Science Department, Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany. rene@bioinf.uni-sb.de|Computer Science Department, Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany. rene@bioinf.uni-sb.de|Computer Science Department, Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany. rene@bioinf.uni-sb.de|Computer Science Department, Center for Bioinformatics, Saarland University, 66041 Saarbrücken, Germany. rene@bioinf.uni-sb.de