what is ramachandran space?

From: wei <weiz.,at,.mail.rochester.edu>
Organization: university of rochester
Subject: what is ramachandran space?
Date: Mon, 17 Feb 2003 10:43:23 -0500

Dear All:
 Could anybody explain to what is "ramachandran space"? I will
 appreciate it.
 Best Regards
 Wei Zhuang
 University of Rochester