140 INTRODUCTION TO IMMUNOCHEMICAL SPECIFICITY 



References for Table 10-1 : 



1. Baker, M. C, D. H. Campbell, S. I. Epstein, and S. J. Singer, 1956, 

 /. Am. Chem. Soc. 78, 312. 



2. Boyd, W. C, J. B. Conn, D. C. Grcgs', G. B. Kistiakowsky, and R. M. 

 Roberts, 1941, /. Biol. Chem. 139, 787. 



3. Carsten, M. E., and H. N. Eisen, 1955, /. Am. Chem. Soc. 77, 1273. 



4. Epstein, S. I., P. Doty, and W. C. Boyd, 1956, /. Am. Chem. Soc. 78, 

 3306. 



5. Haurowitz, P., C. F. Crampton, and R. Sowinski, 1951, Federation Proc. 

 10, 560. 



6. Karush, P., 1950, /. Am. Chem. Soc. 72, 2705. 



7. Karush, P., 1956, /. Am. Chem. Soc. 78, 5519. 



8. Karush, P., 1957, /. Am. Chem. Soc. 79, 3380. 



9. Singer, S. J., and D. H. Campbell, 1955, /. Am. Chem. Soc. 77, 3499. 



10. Singer, S. J., and D. H. Campbell. 1955, /. Am. Chem. Soc. 11, 4851. 



11. Smith, E. L., et al., 1952, /. Biol. Chem. 199, 789. 



12. Steiner, R. P., C. Kitzinger, and T. H. Benzinger, 1956, Research Rept. 

 Vaval Med. Research Inst. 14, 73. 



Significance of Thermodynamic Constants 



The figures in Table 10-1 present some unexpected features. Most 

 surprising, perhaps, is that AF° is generally not large ; —9 kcal per 

 mole seems to be about an upper limit. This is not a large value for 

 standard free energy changes. The free energy of formation of water, 

 for example, is — 54.65 kcal. per mole (for two hydrogen-oxygen 

 bonds) ; that of carbon monoxide is —33.0 kcal. per mole (for one 

 carbon-oxygen bond). On the other hand, it can be seen from Fig. 

 10-3 that the free energy changes involved in the formation of the 

 antibody-antigen bond are sufficient to cause the reaction to go sub- 

 stantially to completion if the reagents are concentrated. (This figure 

 shows the relation between the equilibrium constant K and the free 

 energy change. Also shown is the per cent of product B at equilibrium 

 in a hypothetical reaction A ^ B.) 



Not only are the values of AF° small by physical and chemical 

 standards, but the values for the different reactions are surprisingly 

 alike, suggesting that no antibody-antigen reaction is likely to have 

 a large free energy change. If antibody is formed through contact 

 with a molecule or portion of a molecule of antigen or with some 



