Synopsis'"C-nmr spectra of red seaweed galactans, belonging to the agar and carrageenan groups or having the "intermediate" type of structure, were interpreted on the basis of ':'C-nmr spectra of model compounds. Signal assignments have been made for most of the known extreme structures of such galactans. 'T-nmr spectroscopy was shown to be a rapid and convenient method of structural analysis, which permits one to determine the type of galactan structure, the absolute configurations of its constituents (galactose and 3,6-anbydrogalactose), and the positions of the sulfate and 0-methyl groups in a polysaccharide molecule.
The cell-wall teichoic acids of Nocardiopsis dassonvillei IMRU 509T, IMRU 504 and IMRU 1250 and Nocardiopsis antarcticus VKM Ac-836T have the same unique structure that has not heretofore been found in bacteria. The polymer is built of 10 to 13 repeating units: -1snGro3-P-3-beta-D-GalNAc1-2snGro3-P-. The structure has been established by chemical analysis and with NMR spectroscopy. A study of the cell-wall monosaccharide composition, peptidoglycan, and cell phospholipids also provides evidence for the close similarity of these two species.
In a number of bacteria an unusual glycosyl pyrophosphate (31P NMR signal chemical shift at about −15 ppm) was detected when the cells were subjected to oxidative stress. This substance from Brevibacterium ammoniagenes has now been identified as 2‐methyl‐butan‐1,2,3,4‐tetraol‐2,4‐cyclopyrophosphate, which is accumulated in the cell under certain conditions in concentrations of about 50 mM. It is now suggested that this compound is the long sought after bacterial antistressor.
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