Specificity of the Loiidoii-Eisenschitz- 

 Waiig Force 



Jerrold M. Yos/ William L, Bade,- and Herbert Jehle^ 

 Department of Physics, University of Nebraska, Lincoln, Nebraska 



IN A NUMBER OF BIOLOGICAL PHENOMENA and in some crystallization and 

 polymerization effects, there is evidence of an attractive intermolecular 

 force which is "specific" in that identical or nearly identical molecules 

 interact more strongly than non-identical ones. H. J. ^fuller (1922, 1937, 1941, 

 1947) pointed out that biological evidence indicates the existence of such a 

 specific attraction acting over distances at which the interacting molecules 

 are not in contact, and urged physicists to investigate whether any of the known 

 intermolecular forces was capable of accounting for such a phenomenon. The 

 present paper investigates the conditions under which the London-van der 

 Waals dispersion force between particles immersed in a medium will constitute 

 such a specific attraction. (The London force between two molecules is due to 

 the net effect of interaction of the fluctuating electric dipole moments in one 

 molecule with those of the other.) In the final section of the paper some of the 

 biological implications of the work are discussed, but these remarks must be 

 regarded as highly speculative until the magnitude of the specific London- 

 van der Waals attraction has been established for the various molecules in- 

 volved. 



Observed specificity effects may involve a variety of forces. If the interact- 

 ing molecules can approach one another closely, the most important interac- 

 tions are bond and bridge formation, in particular those between complemen- 

 tary structures (Watson-Crick helix), electrostatic interaction of complementary 

 charge distributions, and van der Waals stabilization of those complementary 

 structures which permit a closest fit. These interactions account for many 

 biological specificity effects (Pauling, 1940; idem, 1948; Haurowitz, 1950; 

 Breinl and Haurowitz, 1930; ]Mudd, 1932; Alexander, 1931), and usually play 

 the decisive role in crystal formation. The simple lock and key picture charac- 

 terizes these interactions. 



1 NSF predoctoral fellow, 1954-56; at present at Harvard University. 



2 At present NSF postdoctoral fellow, Sterling Laboratory of Chemistry, Yale 

 University. 



^ On leave of absence at Gates, Crellin and Church Laboratories, California Insti- 

 tute of Technology. Paper presented by this author. 



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