#  Jonathan M. Levin, Barry Robson, Jean Garnier:
#  "An algorithm for secondary structure determination in proteins based on
#  sequence similarity."
#  FEBS Letters 205(2): 303-308 (1986).
#  Figure 1.
#  PMID 3743779
   A  C  D  E  F  G  H  I  K  L  M  N  P  Q  R  S  T  V  W  Y
A  2  0  0  1 -1  0  0  0  0  0  0  0 -1  0  0  1  0  0 -1 -1 
C  0  2  0  0 -1  0  0  0  0  0  0  0  0  0  0  0  0  0 -1 -1 
D  0  0  2  1 -1  0  0 -1  0 -1 -1  1  0  0  0  0  0 -1 -1 -1 
E  1  0  1  2 -1  0  0 -1  0 -1 -1  0 -1  1  0  0  0 -1 -1 -1 
F -1 -1 -1 -1  2 -1 -1  1 -1  0  0 -1 -1 -1 -1 -1 -1  0  0  1 
G  0  0  0  0 -1  2  0 -1  0 -1 -1  0  0  0  0  0  0 -1 -1 -1 
H  0  0  0  0 -1  0  2 -1  0 -1 -1  0  0  0  0  0  0 -1 -1  0 
I  0  0 -1 -1  1 -1 -1  2 -1  0  0 -1 -1 -1 -1 -1  0  1  0  0 
K  0  0  0  0 -1  0  0 -1  2 -1 -1  1  0  0  1  0  0 -1 -1 -1 
L  0  0 -1 -1  0 -1 -1  0 -1  2  2 -1 -1 -1 -1 -1  0  1  0  0 
M  0  0 -1 -1  0 -1 -1  0 -1  2  2 -1 -1 -1 -1 -1  0  0  0  0 
N  0  0  1  0 -1  0  0 -1  1 -1 -1  3  0  1  0  0  0 -1 -1 -1 
P -1  0  0 -1 -1  0  0 -1  0 -1 -1  0  3  0  0  0  0 -1 -1 -1 
Q  0  0  0  1 -1  0  0 -1  0 -1 -1  1  0  2  0  0  0 -1 -1 -1 
R  0  0  0  0 -1  0  0 -1  1 -1 -1  0  0  0  2  0  0 -1  0 -1 
S  1  0  0  0 -1  0  0 -1  0 -1 -1  0  0  0  0  2  0 -1 -1 -1 
T  0  0  0  0 -1  0  0  0  0  0  0  0  0  0  0  0  2  0 -1 -1 
V  0  0 -1 -1  0 -1 -1  1 -1  1  0 -1 -1 -1 -1 -1  0  2  0  0 
W -1 -1 -1 -1  0 -1 -1  0 -1  0  0 -1 -1 -1  0 -1 -1  0  2  0 
Y -1 -1 -1 -1  1 -1  0  0 -1  0  0 -1 -1 -1 -1 -1 -1  0  0  2 
