Proton Affinity Values for Amino Acids

Amino Acid

PA kcal/mol Relative to NH3

(PA = 205 kcal/mol)

Glycine 211.6
Alanine 214.8
Cysteine  
Serine 216.5
   
   
Valine 218.3
Aspartic Acid 218.6
Leucine 218.9
Threonine 219.2
Isoleucine 219.2
Phenylalanine 220.9
Tyrosine 220.7
Methionine 220.9
   
   
Asparagine 222.1
Glutamic Acid 222.3
Proline 222.4
   
   
Tryptophan 224.3
   
   
Glutamine 227.1
Lysine 228.7
Histidine 230.5
   
   
Arginine 245.0