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Interaction properties of tropocollagen are markedly altered by treatment with pepsin. This treatment liberates terminal or near-terminal covalently bonded peptides whose amino acid composition is strikingly different from the composition of the pepsin-resistant triple-helix body of the macromolecule. Pepsin also converts most of the beta-chains to alpha-chains. This fact indicates that the interchain link is also external to the body of the macromolecule and probably involves peptides. The role of these properties in bioregulative mechanisms is briefly discussed.

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Reaction orders have been determined for the oxidation of three aldehydes, four ketones, and two nitroparaffins by alkaline femcyanide. Oxidation occurs only after these substances have been converted into the anions of their enolic or aci-forms. The reacting systems do not catalyse X-inyl polymerisation and it is concluded that the oxidisable anions form complexes with pe(CN),]S-and are then attacked by more ferricyanide. SINCE the system * Red. + (Fe(CN)J3-Ox. + {Fe(CN),}4-involves one-electron