BARBARA W. LOW AND JOHN T. EDSALL 



residue C„ - C„+i will coincide with the plane of the residue 1-2. 

 The angle between two successive planes is the helical angle 

 2)60 /n = xj/, where n is the number of residues per complete turn. 





Fig. 4. Drawings of the left-handed and right-handed a-helices. 

 The R and H groups on the a-carbon atom are in the correct position 

 corresponding to the known configuration of the L-amino acids in pro- 

 teins. L. Pauling and R. B. Corey, unpubUshed drawings. 



Each residue is tipped down (in the plane) from the horizontal 

 position for Gi - C2 through a vertical distance P/n, where P is 

 the pitch of the final coil. The resultant of the horizontal (180 — 



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