1. Institute for Bioscience and Biotechnology Research and Department of Cell Biology and Molecular Genetics; University of Maryland; Rockville Maryland 20850
2. Genome Center; University of California; Davis California 95616
3. University of Basel, Biozentrum & SIB Swiss Institute of Bioinformatics; Basel Switzerland
4. Department of Physics and Istituto Pasteur-Fondazione Cenci Bolognetti; Sapienza University of Rome; 00185 Rome Italy