An X‐ray diffraction investigation of poly‐ε‐carbobenzoxy‐ l ‐lysine and a complex form of poly‐γ‐methyl‐ l ‐glutamate

X-ray diagrams from oriented fibers of poly-s-carbobenzoxy-T,-lysine and a n e w form of poly7-methyl-T,-glutamate have been obtained. Spacing calculations and rough equatorial intensity measurements from the poly-s-carbobenzoxy-L-lysine photographs indicate tha t the molecules of this substance have the 3.60-residue a-helix configuration with one molecule in a simple hexagonal unit cell, a 0 ----16.69 and c o = 26.90 ~. The interpretation of the poly-y-methyl-L-glutamate photographs is more difficult, but seems to show that a monoclinic unit cell, a = 29.22, b = 8-39, c ---26.84 A, and fl = 110.0 °, is the only one that satisfactorily explains both the X-ray data and the observed density of the fibers. The structure of the molecules in this form is probably based on the 3.60-residue c~-helix, but there is some evidence which indicates that the helical configuration may be distorted slightly.