52 YOS, BADE AND JEHLE 



and prevent wrong molecules from messing up the correct replication. — When 

 the accuracy of replication of a particular mode of folding is under discussion, 

 it is conceivable that in the case of protein folding, the particular amino acid 

 sequence by itself safeguards a unique way of folding characteristic for that 

 sequence (Pauling); it seems, however, that the London force greatly helps to 

 achieve correct folding in the manner discussed along Fig. 5 below). In short 

 it seems that in addition to intramolecular bond and steric requirements, an- 

 other ordering principle is necessary and the present approach suggests that 

 London force specificity is to be considered to provide for the essential first 

 step, i.e. for the selective collection and adequate orientation of the constituent 

 molecules which are going to form the replica. How the replica formation is to 

 be achieved in detail is certainly an unsolved problem (as is the formation of 

 proteins from the information laid down into nucleic acid genes). A few specu- 

 lative suggestions which may indicate the broad outlines of the assembly proc- 

 ess may be sketched in the following; the scheme may be quite different (a) in 

 the problem of the building of a replica of a helix or of a sheet, and (b) in the 

 problem of folding of a chain or helix, or several chain or helix segments in to 

 a still larger compact unit. 



(b) This assembly process may be considered first. In particular the replica- 

 tion of a globular shaped large compact unit which is made up (top part of Fig. 

 5) from several constituent molecules which might be held together by bonds. 

 Constituent molecules for the daughter unit are selected from the surrounding 

 medium and will be oriented with respect to their counterparts in the original 

 unit as indicated in Fig. 5. But that also makes the relative orientation of the 

 constituent molecules of the daughter unit identical with the relative orienta- 

 tions of their counterparts in the original unit. Thus there is a good chance 

 for the molecules of the daughter unit to assemble correctly. Mistakes made in 



^n^^ 



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