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The crystal structure of deuterated benzene has been refined by single-crystal neutron diffraction analysis at 15 and 123 K. The unit-cell dimensions were also measured at 52.6 and 80 K, and the thermalexpansion coefficients at all four temperatures were calculated. The molecules have C 3v symmetry with a small chair-distortion from D 6h , which is possibly significant for the carbon atoms and significant for the deuterium atoms. The mean observed bond lengths at 15 K [123 K] are C-C = 1.3972(5) Å [1.3940(9) Å] (1 Å = 10 -10 m = 10 -1 nm); C-D = 1.0864(7) Å [1.0838(10) Å]. When corrected for molecular libration, the corresponding rest values are 1.3980 Å [1.3985 Å]; 1.088 Å [1.088 Å]. Ab initio molecular orbital calculations at the MP-2/6-31G* level gave energy-optimized bond lengths of 1.395 and 1.087 Å for the isolated molecule at rest, in agreement with the corrected values from the crystal structure within the experimental errors.

Ferritin is the major iron-storage protein present in all cells. It generally contains 24 subunits, with different ratios of heavy chain (H) to light chain (L), in the shape of a hollow sphere hosting up to 4500 ferric Fe atoms inside. H-rich ferritins catalyse the oxidation of iron(II), while L-rich ferritins promote the nucleation and storage of iron(III). Several X-ray structures have been determined, including those of L-chain ferritins from horse spleen (HoSF), recombinant L-chain ferritins from horse (HoLF), mouse (MoLF) and bullfrog (BfLF) as well as recombinant human H-chain ferritin (HuHF). Here, structures have been determined of two crystal forms of recombinant human L-chain ferritin (HuLF) obtained from native and perdeuterated proteins. The structures show a cluster of acidic residues at the ferrihydrite nucleation site and at the iron channel along the threefold axis. An ordered Cd2+ structure is observed within the iron channel, offering further insight into the route and mechanism of iron transport into the capsid. The loop between helices D and E, which is disordered in many other L-chain structures, is clearly visible in these two structures. The crystals generated from perdeuterated HuLF will be used for neutron diffraction studies.

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