摘要: THE MOST DETAILED knowledge we have of the secondary and tertiary structure of insulin is derived from the interpretation of an electron-density map calculated in 1969 from X-ray diffraction measurements made on rhombohedral crystals of insulin containing zinc (2, 5, 6). This map provides evidence of the relative positions in space of all the amino acid residues in the insulin molecules in the particular crystals examined. This evidence is limited by the extent of the measurements and calculations made so far; it is very desirable to understand both the strength and limitations of the experiments from which the atomic arrangement is derived.