232 
The  Nomenclature  of  the  Proteins. 
A.m.  Jour.  Pharm. 
May,  1907. 
8,  Derivatives  of  proteins.  Of  these  the  products  of  protein- 
hydrolysis  (a  term  preferable  to  proteolysis1)  are  those  which  require 
special  attention.    These  should  be  classified  as  follows: — 
(a)  Meta-proteins.  This  is  suggested  in  place  of  albuminate 
(acid-albumin,  alkali-albumin),  which  is  objectionable  because  (i) 
these  products  are  obtainable  from  both  albumins  and  globulins, 
also  (2)  because  the  termination  ate  implies  a  salt. 
(£)  Proteoses.  This  term  includes  albumose,  globulose,  gelatose, 
etc.  The  sub-division  of  these  into  proto-,  hetero-,  deutero-proteoses, 
etc.,  and  the  various  modifications  of  Kiihne's  original  classification 
have  been  considered ;  the  whole  subject  is,  however,  at  present  too 
unsettled  for  any  final  nomenclature  of  these  sub-divisions  to  be 
proposed. 
(c)  Peptones.  This  term  should  be  restricted  to  the  further  pro- 
ducts of  hydrolysis  which  differ  from  the  proteoses  inasmuch  as 
they  cannot  be  salted  out  from  solution  and  usually  resemble  them 
in  giving  the  biuret  test. 
N.B. — It  has  been  pointed  out  that  certain  vegetable  products 
hitherto  regarded  as  peptones  do  not  give  the  biuret  test.  It  does 
not  appear  possible  to  bring  such  exceptional  substances  into  any 
general  classification  at  present.  The  same  difficulty  in  classifying 
arises  in  connection  with  certain  other  vegetable  proteins ;  for 
instance,  those  which  like  gliadin  are  soluble  in  alcohol. 
(d)  Polypeptides.  The  majority  of  the  polypeptides  are  synthet- 
ical substances.  Some,  however,  have  been  separated  from  the 
products  of  protein-hydrolysis,  and  it  is,  therefore,  advisable  to 
include  them  in  the  present  classification.  They  are  .products  of 
cleavage  beyond  the-  peptone  stage,  and  consist  of  two  or  more 
amino-acids  in  association  ;  the  majority  of  those  hitherto  prepared 
do  not  give  the  biuret  test. 
IV.  The  term  caseinogen  should  be  used  for  the  principal  protein 
in  milk  and  casein  for  its  derivative,  which  is  the  result  of  the  action 
of  rennet. 
1  Although  mindful  of  the  unfortunate  fact  that  terms  such  as  proteolysis 
fail  to  convey  a  meaning  in  harmony  with  that  which  is  conveyed  by  the  term 
electrolysis  and  hydrolysis  (on  which  they  are  moulded)  of  decomposition  by> 
the  Committee  have  not  ventured  to  deal  with  the  difficulty ;  they  recognize, 
however,  that  the  practice  is  one  to  be  obviated,  if  possible  (compare  Armstrong, 
Proc,  Roy.  Soc,  1904,  73,  500). 
