254 



Walter Gordy 



hydrogen bridges have all orientations with the field from to 180°. With this 

 arrangement one would expect the individual components of the doublet to 

 be broader and less well resolved than for the parallel case. These features are 

 not completely in accord with the observed results on silk. The doublet 

 splitting for = (parallel case) is found to be approximately 25 gauss, some- 

 what larger than that previously estimated from the polycrystalline material, 

 and also significantly larger than that expected for the hydrogen bonded model. 



H 



O 



C 



CRN 



H 



/b 



O 



I 



H 



N RIC 



/ \\A \ 



C \ N 



+ 



H 



H 



H 



(I) 



H 



(II) 



Furthermore, the separation of the doublet seems to be greater for the 

 parallel case. 



It should be appreciated that what is proved for silk is simply that the 

 radical formed is one in which the odd electron interacts with one and only one 

 proton, and that this interaction is at least partly anisotropic. Later we 

 hope to obtain more specific evidence from deuterium substitution in glycyl 

 glycine, which appears to have the same doublet as that for silk. 



Irradiated feather quill gives a composite pattern of a doublet and the 

 cysteine-like resonance. However, the doublet is not as widely spaced as that 

 for silk and is not resolved for a polyoriented sample. It has been found (19) 

 that the strong component to the left of the cysteine-like resonance in feather quill 

 (Fig. 11) is partially resolved into a doublet when the feather quill is arranged 

 parallel to the applied magnetic field, whereas it has only about half the width 

 of the unresolved resonance for the perpendicular orientation. Presumably the 

 structure of the feather quill is that of the alpha helix of Pauling and Corey 

 (27), with the helix axis along that of the quill. Interestingly, the cysteine- 

 like component of the resonance is not orientation-dependent. We believe for 

 reasons given later that this situation indicates that the S — S or the C — S bonds 

 of the quill have many different orientations with respect to the quill axis. 



A resonance found to be prominent in x-irradiated proteins which contain 

 sulfur is like that of cystine, shown in Fig. 4. Biological substances such as 

 hair (Fig. 9), hoof, horn, and feather have this as the predominant if not the 



