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Hemocyanins are large multi-subunit copper proteins that transport oxygen in many arthropods and molluscs. Comparison of the amino acid sequence data for seven different subunits of arthropod hemocyanins from crustaceans and chelicerates shows many highly conserved residues and extensive regions of near identity. This correspondence can be matched closely with the three domain structure established by x-ray crystallography for spiny lobster hemocyanin. The degree of identity is particularly striking in the second domain of the subunit that contains the six histidines which ligate the two oxygen-binding copper atoms. The polypeptide architecture of spiny lobster hemocyanin appears to be the same in all arthropods. This structure must therefore be at least as old as the estimated time of divergence of crustaceans and chelicerates, about 540 to 600 million years ago.

Turanose, C 12H22011, is a disaccharide of tt-D-glucose and fl-D-fructose, linked ¢t-1-.3, with fructose as the reducing unit. Turanose is orthorhombic, space group P212~2 . with a = 8.153 (3), b = 9-205 (2), c = 19.251 (7) A and Z = 4. The structure was solved by direct methods and refined to a final R of 0.031 for 1404 counter reflexions. The glucose ring has the usual 4CI pyranoside chair conformation. In contrast to all known fructose-containing oligosaccharides where the fructose moiety occurs in several variations of furanoside twist and envelope conformations, the fructose ring in turanose represents a unique case in that it adopts the 2C 5 pyranoside chair conformation of free fl-o-fructose. The conformations about the exocyclic C-C bonds of the glucose and fructose units are gauche-gauche and gauche-trans respectively and differ from that of it-D-glucose (gauche-trans) and fl-o-fructose (gauche-gauche). The conformation of the glycosidic ~-1-.3 linkage is analogous to that of the t~-l-*4 linkage of maltosides. Of the eight potential hydrogen-bond donors, one hydroxyl group does not act as a donor and another hydroxyl group interacts with an acceptor at a distance of 3-031 ,~ with O-H...O 134 °, and should be considered as a weak interaction. Accordingly, the IR spectrum shows two sharp absorption maxima at frequencies near that of an unperturbed OH-group stretch vibration. One of the hydrogen bonds is intramolecular.

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