||Pauling, L Corey, RB Branson, HR (1951). "The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain". Proceedings of the National Academy of Sciences of the United States of America 37 (4): 205–211 p.209 2nd paragraphPubMed ID14816373
||P.205 top paragraph:"During the past fifteen years [investigators] have been attacking the problem of the structure of proteins in several ways. One Of these ways is the complete and accurate determination of the crystal structure of amino acids, peptides, and other simple substances related to proteins, in order that information about interatomic distances, bond angles, and other configurational parameters might be obtained that would permit the reliable prediction of reasonable configurations for the polypeptide chain."
||P.209 2nd paragraph:"The translation along the helical axis in the 3.7-residue helix is 1.47 Å, and that in the 5.1-residue helix is 0.99 Å. The values for one complete turn are 5.44 Å And 5.03 Å, respectively. These values are calculated for the hydrogen-bond distance 2.72 Å they would have to be increased by a few per cent, in case that a larger hydrogen-bond distance (2.80 Å, say) were present." Keywords:protein,secondary structure,size,length