X-ray analysis, circular dichroism, receptor binding and biological potencies of chemically modified insulins suggest that the conformation of the insulin molecule is critical to the formation of both the zinc insulin hexamer and the insulin-receptor complex. Results are consistent with an insulin receptor-binding region including many of the hydrophobic residues important to dimerisation in addition to more polar surface residues. There is a further possibility of formation of an antiparallel sheet structure between the insulin and receptor molecules in the complex similar to that between monomers in the insulin dimer.

A hexapeptide obtained from human casein by enzymatic digestion has been purified, sequenced and synthesized; its structure is: Val‐Glu‐Pro‐Ile‐Pro‐Tyr. In vitro this hexapeptide stimulates the phagocytosis of opsonized sheep red blood cells by murine peritoneal macrophages. Administered intravenously to adult mice, it enhances the resistance to infection with Klebsiella pneumoniae.

Staying in the tradition of Astbury's hypothesis about the role of the α ⇔ β transformation for the stress/ strain-curve of wool fibers and of Feughelman's X/Y-zones model, the interrelation between the morphological structure of keratin fibers and the shape of their stress/strain-curve in water is reevaluated. The yield and post-yield regions can be attributed to the opening up of two distinctly different and well defined portions of the monomer of the intermediate filament; the increased slope in the postyield region can be attributed to the influence of the sulfur bonds in one of the segments.The role of the sulfhydryl-disulfide interchange reaction for the appearance of the post-yield region is pointed out and the molecular mechanisms for achieving the maximum possible strain are discussed.J. B. Speakman was the first prominent protagonist of the theory that the mechanical properties of wool fibers have an important influence on their processing performance. In consequence, he placed a major emphasis on measuring stress/strain-curves and their changes with physical and chemical modifications [ 29 ] . The upper curve in Figure 1 shows somewhat schematically the stress/strain curve of a wool fiber in water. FIGURE 1. Stress/strain curve of a wool fiber in water (schematically ) and the components of the two-phase model. Stress and strain are not drawn to scale. _ On the molecular level, structural investigations using x-ray diffraction led to the discovery of axially oriented a-helices by Pauling and Corey and of the ahelix b 0-pleated sheet transformation with strain by Astbury and Woods. Studies by transmission electron microscopy revealed the existence of lightly stained cylindrical structures, traditionally referred to as &dquo;microfibrils,&dquo; embedded in a more darkly stained &dquo;matrix&dquo; phase [ 16 ] .On the basis of knowledge of the microscopic and molecular morphology of a-keratin fibers, major attempts have been made, especially by Hearie et al. [ 21,22 ] and Feughelman [ 15 ] , to consistently interpret the shape of the stress/strain-curve in relation to fiber structure. Both these approaches are based on the twophase model proposed by Feughelman [ 10 ] , where the filament phase dominates the stress/strain curve in the wet state, while the amorphous matrix phase either plays a minor role [ 15 or exhibits a significant contribution only at high strains [ 21,22 ] .Si nce these versions of the structure / property relationships [ 15,22 ] , more detailed information has become available on the structure of the &dquo;microfibrils,&dquo; in modern semantics referred to as &dquo;intermediate filaments.&dquo; This has enabled us, when expanding a previous account of our research [ 39 ]. to reevaluate the models on a molecular level. The model refinement, which stays in the tradition of Feughelman's X/Yzones model [ 1 l ,15 ] , achieves an improved consistency of the property / structure relationship. Structural Principles and Stress/Strain Properties of Fibrous Keratins a-Keratin f...

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The most prominent view of the diffusion mechanism of dyes into wool fibers assumes that the molecules primarily enter the fiber in a fast process along the cell membrane complex (CMC), that is, by an intercellular mechanism. From the CMC, they are subsequently distributed in a slower process throughout the other morphological components according to their respective diffusion coefficients and dye affinities. This view, referred to here as the CMC-diffusion model, is based on investigations of the diffusion performance of heavy metal complex and fluorescent dyes under anhydrous and aqueous conditions. An evaluation of various key aspects of the evidence for this model suggests that, due to differences in the glass transition and fluorescence quenching performance of the various morphological components in a wool fiber, there is, in fact, little evidence to support the CMC-diffusion model. Instead, the evidence supports the alternative, more general view that under normal dyeing conditions, diffusion proceeds primarily by means of all the nonkeratinous components of the wool fiber according to a restricted transcellular diffusion mechanism.

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