The application of five water-soluble, halogen-free, alkylammonium-based ionic liquids (ILs) as additives for advanced crystallization of lysozyme was investigated. Their biocompatibility was determined by long-term measurement of the overall mean relative enzyme activities. These were maximally reduced by about 10-15% when up to 200 g IL l(-1) was added. Sitting-drop vapor diffusion crystallization experiments revealed that the addition of some of the ILs led to less crystal polymorphism and precipitation was avoided reliably even at larger NaCl concentrations. The addition of ILs tended to result in larger crystals. The kinetics of lysozyme crystallization were significantly enhanced using ILs as crystallization additives, e.g. by a factor of 5.5 when 100 g ethanolammonium formate l(-1 )was added. ILs with "soft" anions, such as formate or glycolate, were superior to ILs with "hard" anions, like nitrate.

The use of heptadentate dinucleating ligands is a promising strategy for the synthesis of dinuclear iron complexes that serve as model compounds for metalloproteins. To imitate the respective active sites as well as possible, unsymmetrical ligands are required. The crystallization of the corresponding unsymmetrical iron complexes has proven to be extremely difficult, and to date only two examples, both based on the use of p-phenoxobridged hgdnds. have been described. Latour et al. have successfully synthesized an unsymmetrical Fe"Fe"' complex with terminal phenolato coordination as a model for purple acid phosphatases"] and also prepared a semimet-hemerythrin analogue. ['] We report here on the synthesis and X-ray structure analysis of the first unsymmetrical p-alkoxo-bridged dinuclear iron complex and on its peroxidase activity.

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Fluoroberyllates, Beryllium Fluoride, Ligand Redistribution, NMR Data The composition of aqueous fluoroberyllate solutions has been studied by 9Be and l9F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]_ , and [BeFzi]2 -. These equilibria are shifted towards [BeF4]2_ at high pH. No polynuclear fluo roberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.