90 JOSEPH O. HIRSCHFELDER 



there are photo-stationary states of the system that absorb the hght and very 

 possibly do so in some subsequent steps. 



I beUeve that in a few cases paramagnetic resonance has indicated odd elec- 

 tron spins in systems where they might not have been expected and we do not 

 know whether these are important or not. My general impression was that for 

 most of the biochemical systems, all of the component units of the molecules 

 are in their lowest electronic state and that the explanations are probably to 

 be found in terms of the usual energy potential terms which we recognize in 

 small molecules such as hydrogen bonds, rotational potentials, van der Waals 

 forces of a relatively local type, etc. I think I would be most interested to hear 

 if there are numerous cases where excited electronic states have been identified. 



Chairman Pauling: My feeling has been the same as that of Professor Pitzer, 

 that in biological systems, excited states of molecules are not important except 

 as part of reaction mechanisms. 



Professor Jehle: Excited states are indeed interesting only in that thermal 

 accessibility of excited states limits the specificity. We have analyzed this in 

 the paper already referred to, where we stated four conditions for the specificity 

 to be effectively a many-parametric one. A manifold of macromolecules may 

 show specific discrimination if the molecules possess sufficiently diversified 

 (with respect to frequency distribution) and strong polarizabilities, provided 

 these frequencies are well above the classical domain. 



