PROTON AFFINITY OF ARGININE MEASURED BY THE KINETIC APPROACH

The proton affinity of arginine is obtained from the kinetic method of dissociation of proton-bound dimers, as 245.2 kcal/mol with an uncertainty of +/-0.5 kcal/mol. This value is about 14 kcal/mol higher than that of histidine, the next most basic of the commonly occurring mammalian amino acids, in contrast to the average difference of 1 kcal/mol between the other 19 amino acids. The order of proton affinity of these 20 amino acids is also determined and discussed.