The Lotmar–Picken X-Ray Diagram of Dried Muscle

Abstract

DURING the past twenty-five years, four samples of dried muscle have been made which show a striking X-ray diagram, with sharp diffraction maxima superimposed on the α-keratin pattern usually obtained from muscle. These samples of muscle were from the frog (sartorius muscle, Herzog and Jancke¹), the mussel Mytilus edulis (Lotmar and Picken²; we have been informed by these authors that the muscle used was the anterior byssal retractor, rather than the posterior adductor, as stated in their paper), the scallop Pecten (adductor muscle, Bear and Cannan³), and the squid Loligo (funnel retractor muscle, Bear and Cannan³). Lotmar and Picken proposed a mono-clinic unit of structure, with a₀= 11.70 A., b₀= 5.65 A., c₀= 9.85 A., β = 73.5°, and they suggested that the crystalline substance, assumed to be protein, contains nearly extended polypeptide chains, parallel to the β-axis (the fibre axis), with two of these chains (four amino-acid residues) per unit cell. We have also discussed the X-ray pattern, on the assumption that the crystalline substance is a protein, and have suggested that the structure of the protein is that of the 3.7-residue helix⁴.