The Lotmar–Picken X-Ray Diagram of Dried Muscle

Abstract

THE publication by Lotmar and Picken¹ of an X-ray photograph of a certain dried muscle preparation produced considerable interest and controversy, since, in addition to indicating an unusual degree of crystallinity, the diagram showed no sign of the 5.15 A. meridional arc which hitherto had been regarded almost as a diagnostic feature of the X-ray photographs of α-fibrous proteins. While we do not wish to enter the controversy as to whether or not Lotmar and Picken's photograph is indeed that of myosin, or any other protein, we should in passing like to point out the striking resemblance between their photograph and that of an oriented film of poly-γ-methyl-L-glutamate, published by Bamford, Hanby and Happey². Recently, Pauling and Corey³ have claimed that Lotmar and Picken's results support their suggestion that the polypeptide chains in fibrous proteins have their α-helical configuration, particularly in that the fibre axis translation of 5.65 A. calculated by Lotmar and Picken is in good agreement with the distance in the axial direction between adjacent turns of the α-helix. It is therefore perhaps worth while pointing out that the fibre repeat deduced by Lotmar and Picken is not consistent with certain features of their fibre diagram, and that the true value (or a submultiple) should be about 5.3 A.