THERMAL INACTIVATION OF VIRUSES 



105 



breaking of one bond does not seem to destroy the configuration. 

 The nearby breaking of several does produce a marked collapse, 

 and it is tempting to think of this as the process involved in 

 denaturation. 



Now each bond vibrates, or can do so, and, because it is a 

 confined system, the laws of quantum mechanics require that 



Covalent Bonded Backbone 

 Hydrogen Bonds in Helix 

 Interhelix Bonds 



Fig. 4.1. Schematic representation of the three classes of bond in a protein. 

 The helix has considerable binding energy per bond but the hydrogen bonds 

 in each chain, and the interchain bonds, are weaker. 



only certain restricted vibrational energy levels are possible. We 

 definitely do not intend to go into this whole subject, but we do 

 need to assume that there is a ladder of levels for each form of 

 vibration, and so we will assign to the rth level of a ladder the 

 energy Er. If n of the possible bonds are in the energy level r, 

 and no in that of the ground state, then the most likely configura- 

 tion at a temperature T degrees Kelvin is one for which 



-— = g-Er/kT 



riQ 



(4.1) 



