SPECiriCITY OF LONDOX-EISENSCHITZ-WANG FORCE 45 



If one considers the closest approach of neighboring molecules with an R equal 

 to twice the 'radius' of the molecule, 



R-' = (7r/6 volume)' (18) 



— AiAiu "X kT 2 (7r/6 volume)". 



{{h^xjy/AkT)[Y. aw - E «tiv]' + [E «ci - E «ci]'} (17a) 

 I II I II 



If one considers, as above, I as an average type molecule of a manifold of mole- 

 cule types, the average rearrangement free energy (of quadruplets of molecule 

 types) is 



(— A4y4iii)Av ^ mean square deviation of 



[2kT ihuuv/^kT)]' (x/6 volume) E «uv 



plus that of 



[2kTf (7r/6 volume) E «ci (17b) 



In order to get an idea of the magnitudes of these quantities, without going 

 into detailed assumptions about the manifold of molecule types under considera- 

 tion, one can estimate the squares of the quantities listed in (17b) for typical 

 molecules instead of their mean square deviations for a manifold of molecules. 

 As a first step in estimating the size of the ultraviolet terms, one can add up 

 the atomic static polarizabilities of the atoms occurring in a glycine residue and 

 gets, (taking as effective oscillator strength E/ ^^^ ^^^^ o^ the number of 

 electrons in the valence shells, i.e. 11) E «uv ~ 7.5-10~24 cml The fre- 



residue 



quency is estimated from the ionization energy as wuv ^ 2-10'^ sec~^ and the 

 volume per residue ^ 60-10~'-'* cm^ This brings the square of the UV term 

 listed in (17b) up to 1.1 kT. 



Actually one has to study molecular electronic states and their polariza- 

 bilities rather than atomic polarizabilities. Of particular interest are electronic 

 transitions in molecules which correspond to high electron mobility. There are 

 several possibilities which might greatly enhance the importance of UV terms 

 and make them stronger than 1.1 kT, in particular the occurrence of low fre- 

 quency electronic transitions, or the presence of excited electronic states which 

 are in reach of thermal excitation. The quantity w( E ")' which characterizes 

 the square of the ultraviolet term listed in (17b), this Cjuantity is proportional 

 to w~^(E/)'- The total E/ is, by Thomas Reiche Kuhn (Kramers Kronig 

 1928) limited by the number of electrons. A shift of the oscillator strengths 

 towards lower frequencies therefore intensifies the interaction. It also provides 

 for a diversification of the distribution of polarizabilities over several ultraviolet 

 regions. 



For large macromolecules, each of which presents a large number of repeti- 



