Protein Structure and Information Content 121 



specify the identity and sequence of high-gradient transitions. On this basis 

 energy from an absorbed quantum, ionization or thermal process would 

 migrate through the molecule in a fashion represented mainly by a 'low 

 gradient' trajectory. However, once the energy or charge becomes localized 

 in a bond of low ionization potential involved in latching large segments 

 of the molecule together, a 'high-gradient' transition, not readily reversible, 

 would occur. The inactivation efficiency of absorbed energy will thus be 

 a function both of the locus of the molecular state at the time energy is 

 absorbed as well as its resulting trajectory; where the trajectory depends 

 upon the amount of energy introduced, the point of absorption and any 

 external factors which affect the contours on the ED planes. For instance, 

 the quantum efficiency of UV varies considerably with pH for a number of 

 enzymes (47). 



The interdependence of energy, configuration and probability proposed 

 here provides a formalism for depicting enzyme action. It is fairly typical 

 of enzyme, as well as other types of catalysis, that reactions proceed which 

 are normally not feasible because of steric or energetic hindrances. It is entirely 

 possible that because of their large size, enzymes act as large energy reservoirs 

 whose function is to "deliver" a quantity of energy to a particular site or com- 

 plex in an irreversible fashion. Another possibility is that energy may not 

 be delivered per se but as a change in configuration of the enzyme with a 

 corresponding alteration in the spatial relationship between reactants complexed 

 to the enzyme. Within these proposals the formation of the enzyme-substrate 

 complex could have an important function. It could act as an external agent 

 affecting the ED contours so as to cause a directed alteration in trajectory, 

 leading finally to a completed enzyme catalysis. Effective, i.e. rapid and 

 essentially irreversible, enzyme catalysis will likely depend upon (1) an E — S 

 complex formation which involves a high-gradient transition, so as to enhance 

 a drastic alteration in the trajectory of molecular state, and (2) the directed 

 trajectory passing through a high-gradient region, preferably just before 

 completion of catalysis, in order to make reversibility unlikely. 



REFERENCES 



1. H. Branson: Information theory and the structure of proteins. In: Information Theory in 

 Biology, ed. by H. Quastler, 84-104, University of Illinois Press, Urbana (1953). 



2. R. Roberts: Carnegie Institution Yearbook:, No. 55, 110-148 (1956). 



3. D. Cowie: Carnegie Institution Yearbook, No. 55, 110-148 (1956). 



4. L. AuGENSTiNE, H. BRANSON, and E. Carver: A search for intersymbol influences in 

 protein structure. In: Information Theory in Biology, ed. by H. Quastler, 105-118, 

 University of Illinois Press, Urbana (1953). 



5. G. Gamow, a. Rich, and M. Ycas: The problem of information transfer from the 

 nucleic acids to proteins. In: Advances in Biological and Medical Physics 4, ed. by J. H. 

 Lawrence and C. Tobias, 23-68 (1956). 



6. H. MoROwiTZ, et al.: personal communication. 



7. M. Ycas: (preceding paper in this volume). 



8. L. Pauling, R. Corey, and H. Branson: The structure of proteins. Proc. Nat. Acad. 

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9. W. Kauzmann: In: The Mechanism of Enzyme Action, ed. by W. McElroy and B. Glass, 

 Johns Hopkins Press, Baltimore (1954). 



