Computational Biology Center, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA. ruhongz@us.ibm.com|Computational Biology Center, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA. ruhongz@us.ibm.com|Computational Biology Center, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA. ruhongz@us.ibm.com|Computational Biology Center, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598, USA. ruhongz@us.ibm.com