  Ubiquitin, discovered less than 50 years ago, tags thousands of diseased
proteins for destruction. It is small (only 76 amino acids), and is found
unchanged in mammals, birds, fish and even worms. Key features of its
functionality are identified here using critical point thermodynamic scaling
theory. These include Fano interference between first- and second-order
elements of globular surface shape transitions. Comparison with its closest
relative, 76 amino acid Nedd8, shows that the latter lacks these features. A
cracked elastic network model is proposed for the common target shared by many
diseased proteins.
