Cyclization under mild conditions of anthraniloyl- and N-methyl-anthraniloyl dipeptides

Anthraniloyl- and N-methyl-anthraniloyl dipeptides containing C-terminal L and D proline residues have been synthesized and subjected to cyclization reaction under mild conditions. The influence of substituents and of the chirality of the residues on the output of the reaction is discussed.     

Sequential polymerization of flagellin A and flagellin B into Caulobacter flagella

The mode of polymerization of two species of flagellins, flagellin A and flagellin B, in polar flagella of Caulobacter crescentus was examined. By immunological staining we found that 1 to 1.2 μm of the portion of the flagellar filament proximal to the cell was composed of flagellin B, whereas about 5 μm of the distal portion was composed of flagellin A. This result, together with the previous observation that a flagellin B-less mutant cannot form normal flagella but instead forms stubs in spite of their high level of flagellin A synthesis, indicates that flagellin B is very important for the formation of complete flagella and/or for the initiation of filament formation from the hook.     

Improved technique for the isolation of stable mutants ofZymomonas mobilis

Addition of caffeine to the recovering medium after mutagenesis ofZymomonas mobilis by N-methyl-N-nitrosoguanidine increased 4-fold the number of auxotrophic mutants obtained. Moreover, while the mutants isolated without caffeine survived only a few repeated serial transfers on minimal medium supplemented with the required growth factor, 40 % of those obtained in the presence of caffeine were stable.     

Dystrophin in rod spherules; submembranous dense regions facing bipolar cell processes

 It is known that the retina contains the protein dystrophin in the ribbon synapse, but the ultrastructural analysis is not yet fully elucidated. Our previous study reported that dystrophin is localized under the rod cell membranes in rat retinas. In the present study, we have investigated the relationship between dystrophin-rich regions of rod cell membranes and other neuronal processes in mouse retinas with a monoclonal antibody raised against the human dystrophin C-terminus. Immunoblotting, immunofluorescence stainings, and immunoelectron microscopy were employed. Immunoblotting analysis indicated that mouse retinas possessed some of the dystrophin isoforms of approximately 260 kDa, 140 kDa, and 70 kDa molecular weight. Confocal images showed a punctate appearance in the outer plexiform layer, as previously described. Immunoelectron microscopy showed that dystrophin immunoreactive products were always observed at submembranous dense regions of the rod spherule abutting bipolar processes. These results suggest that retinal dystrophin may be closely involved in signal transmission from rods to bipolar cells. Accepted: 7 May 1997     

A simple and efficient synthesis of puromycin, 2,2′-anhydro-pyrimidine nucleosides,cytidines and 2′,3′-anhydroadenosine from 3′,5′-O-sulfinyl Xylo-nucleosides

Synthesis of antibiotics, puromycin and 3 ′-amino-3 ′-deoxy-N ⁶,N ⁶-dimethyladenosine 11 was achieved by utilizing the cyclic sulfite 6a of the xylo-3 ′,5 ′-dihydroxy group as a new protective group. The key synthetic step is the deprotection of the sulfite moiety through the intramolecular cyclization of 2-α-carbamate 7. In a similar manner, 2,2 ′-anhydro-pyrimidine nucleosides 15, ribo-cytidines 17 and 2 ′,3 ′-anhydroadenosine 14 were prepared in high yields from the corresponding sulfites 4, 5, and 6b, respectively.     

Inhibition of chromosome repair by caffeine or isonicotinic acid hydrazide on chromosome damage induced by mitomycin C in human lymphocytes

The frequency of interchromatic exchanges induced by mitomycin C in cultured human lymphocytes was markedly lowered in the presence of caffeine or isonicotinic acid hydrazide (INH) during a post-treatment period. The autoradiographic experiment showed that the decrease in the exchange frequency did not result from delaying or cell-killing effects by the post-treatment with caffeine or INH. Therefore, it may deduced that the exchange formation closely related to a process sensitive to caffeine or INH.