Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class amides [RkE(=O)l(OH)m (l≠0; ≥1 (OH):=(NR2))]
                 Class peptides [H2NCH(R)C(=O)[NHCH(R)C(=O)]nOH]
                   Class polypeptides
                     Class proteins
                       actin
                       bacteriorhodopsin
                       botulinum toxin (BTX)
                       cholera toxin (CTX)
                       diphtheria toxin
                       fibrin
                       fibrinogen
                       globin
                       glycophorin A
                       heat-labile enterotoxin (LT)
                       heat-stable enterotoxin (ST)
                       hemoglobin
                       insulin
                       keratin
                       Class lectins
                       mucin
                       myoglobin
                       myosin
                       Class phycobiliproteins
                       proinsulin
                       prothrombin
                       rhodopsin
                       Shiga toxin (Stx)
                       streptolysin O (SLO)
                       streptolysin S (SLS)
                       tetanolysin
                       tetanospasmin
                       thrombin
                       tropomyosin
                       troponin
                       1 Class scleroproteins
                       2 Class globular proteins