Archive image from page 452 of Currents in biochemical research (1946). Currents in biochemical research currentsinbioche00gree Year: 1946 ( X-RAY DIFFRACTION part of the pattern. It is therefore customary to stop the primary beam with a small lead plate, the shadow of which can be seen in the center of Figure 1. In addition to these spots, one observes a fairly distinct accumulation of scattered intensity in the immediate neighborhood of the incident beam and a faint, but not negligible, diffuse background upon which the diffraction spots are superimposed. Theoretical considerations (see 9,2
Archive image from page 452 of Currents in biochemical research (1946). Currents in biochemical research currentsinbioche00gree Year: 1946 ( X-RAY DIFFRACTION part of the pattern. It is therefore customary to stop the primary beam with a small lead plate, the shadow of which can be seen in the center of Figure 1. In addition to these spots, one observes a fairly distinct accumulation of scattered intensity in the immediate neighborhood of the incident beam and a faint, but not negligible, diffuse background upon which the diffraction spots are superimposed. Theoretical considerations (see 9,24) and extensive experience with x-ray diagrams of many inorganic and organic materials indicate Fig. 1.—X-ray diagram of commercial silk fibroin (silkworm). Beam normal to fiber axis (24). that, under favorable conditions, conclusions of the following character can be drawn from the analysis of such patterns. Mere qualitative inspection permits the conclusion, on the basis of the existence of distinct spots, that the sample investigated contains geometrically organized areas inside of which long-chain molecules of the silk protein are localized in a strictly periodic manner, like the indi- vidual bristles in a paint brush or the single pencils in a package of pencils. The presence of distinct spots instead of rings indicates that these highly ordered domains all have one of their axes parallel (or very nearly parallel) to the common axis of the investigated fibers, 441
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