SynopsisThe values of maximum frequencies, intensities, and other spectral parameters of the main absorption bands of amino acid residue side-chain groups have been obtained in the 1500-1800-cm-1 region for solutions in heavy water at pD 1-12. I t is shown that absorption of residues of asparagine, glutamine, aspartic and glutamic acids, arginine, and tyrosine must be taken into account in quantitative studies of the infrared spectra of polypeptide and protein solutions in heavy water. Examples of separating out the amide I band for ribonuclease A in heavy water are given.

SummaryHaloarchaeal¯agella are composed of a number of distinct¯agellin proteins, speci®ed by genes in two separate operons (A and B). The roles of these¯agel-lins were assessed by studying mutants of H. salinarum with insertions in either the A or the B operon. Cells of the¯gA À mutant produced abnormally short, curved agella that were distributed all over the cell surface. The¯gA2 À strain produced straight¯agella, mainly found at the poles. The¯gB À mutant had¯agella of the same size and spiral shape as wild-type cells, but these cells also showed unusual outgrowths, which appeared to be sacs ®lled with basal body-like structures. In broth cultures of this mutant, the medium accumulated¯agella with basal body-like structures at their ends.

Flagella of the haloalkalophilic archaebacterium Natronobacterium magadii were purified and characterized. The diameter of the flagella was 10 nm. It was shown that the flagella consist of four major proteins with molecular weights of 105 000, 60 000, 59 000, and 45 000. With decreasing NaCl concentration, the flagella dissociated into protofilaments. The structure of dissociated flagella and individual flagellins was studied by limited proteolysis. It was found that proteolytic cleavage of flagellins in dissociated flagella into high molecular weight fragments (about 40 000) did not lead to protofilament degradation. It was shown that the most stable fragment is formed from the 60 000 molecular weight flagellin. Cleavage of this fragment led to complete disappearance of protofilaments. On the basis of the data obtained, possible principles of archaebacterial flagellar construction are discussed.Key words: flagellin, archaebacteria, protofilaments, Natronobacterium magadii.

A method for the difluorohomologation of ketones accompanied by halogenation of a C-H bond is described. The reaction involves silylation, difluorocarbene addition using Me3SiCF2Br activated by a bromide ion, and halogenation of intermediate cyclopropanes with N-bromo- or N-iodosuccinimide. The whole process is performed without isolation of intermediates. The resulting α,α-difluoro-β-halo-substituted ketones can be readily converted into fluorine containing pyrazole derivatives and oxetanes.

Many Archaea use rotation of helical flagellar filaments for swimming motility. We isolated and characterized the flagellar filaments of Haloarcula marismortui, an archaeal species previously considered to be nonmotile. Two Haloarcula marismortui phenotypes were discriminated--their filaments are composed predominantly of either FlaB or FlaA2 flagellin, and the corresponding genes are located on different replicons. FlaB and FlaA2 filaments differ in antigenicity and thermostability. FlaA2 filaments are distinctly thicker (20-22 nm) than FlaB filaments (16-18 nm). The observed filaments are nearly twice as thick as those of other characterized euryarchaeal filaments. The results suggest that the helicity of Haloarcula marismortui filaments is provided by a mechanism different from that in the related haloarchaeon Halobacterium salinarum, where 2 different flagellin molecules present in comparable quantities are required to form a helical filament.