No abstract

The isolation, purification and analysis of the lipid A obtained from Mesorhizobium loti Ayac 1 BII strain is presented. Analysis of the carbohydrate moiety after acid hydrolysis by high-pH anion-exchange chromatography with pulse amperometric detection (HPAEC-PAD) showed the presence of glucosamine and galacturonic acid as the only sugar components. Gas chromatographic (GC) and GC/mass spectrometric (MS) analysis of the fatty acids revealed the presence of 3-OH-C12:0; 3-OH-C13:0; 3-OH-C20:0 and 27-OH-C28:0 among the major hydroxylated species. In addition, C16:0, C17:0, C18:0 and C 20:0 were shown as main saturated fatty acids. Different polyacylated species were evidenced by thin layer chromatography of lipid A, allowing the purification of two fractions. Ultraviolet matrix-assisted laser desorption/ionization time-of-flight (UV-MALDI-TOF) MS analysis with different matrices, in the positive- and negative-ion mode, was performed. The fast moving component revealed the presence of hexa-acylated species, varying in the fatty acid composition. Species containing three 3-OH fatty acids and a 27-OH-C28:0 fatty acid were observed. Individual ions within this family differ by +/-14 mass units. The slow moving component was enriched mainly in penta-acylated species. Among them, three subgroups were detected: the major one compatible with the sugar core bearing two 3-OH 20:0 fatty acids, a 3-OH 13:0 or a 3-OH 12:0 fatty acid, a 27-OH 28:0 fatty acid and one saturated fatty acid. Each signal differs in a C18:0 acyl unit from the corresponding hexa-acylated family. On the other hand, a subgroup bearing one 3-OH 20:0 fatty acid, one 27-OH 28:0 fatty acid and two non-polar fatty acids was shown. A minor subgroup compatible with structures containing two hydroxylated and three non-polar fatty acids was also detected. The results obtained showed that nor-harmane was an excellent matrix for charged lipid A structural studies in both, positive and negative ion modes.

Dedicated to Prof. Rosa M. de Lederkremer on occasion of her 70 th anniversaryAbstract A partially cyclized mu/nu-carrageenan from Gigartina skottsbergii was submitted to autohydrolysis and the resulting mixture of oligosaccharides was fractionated using sequential dialysis through tubings of molecular weight cutoff 12000, 3500 and 1000. In this way four fractions were separated and characterized. Structural analysis of the major fraction, obtained from the solution inside the dialysis tubing of molecular weight cutoff 12000 (D120), was carried out. A significant difference was found by 13 C NMR spectroscopy and UV-MALDI-TOF mass spectrometry: in the 13 C NMR spectrum the reducing end-chain unit was the hydrated aldehyde of 3,6-anhydrogalactose while the UV-MALDI-TOF mass spectrum showed an unimodal distribution of even and odd peaks, suggesting fragmentation of glycosidic linkages.

No abstract

No abstract