The structure of capsular polysaccharide of the Pneumococcus type II.

The pneumococcus type II capsular polysaccharide (SII) is composed of singly-branched hexasaccharide repeating units, for which three alternative structures have been proposed. The correct structure has now been determined by consecutive eliminations of the sugar residues in the side chain. The terminal D-glucuronic acid group was eliminated by treating the fully methylated and esterified SIIpolysaccharide first with base, and then with weak acid. The hydroxyl group at C-6 in the penultimate D-glucose residue released by this elimination was transformed into the 6-deoxy-6-tosyl derivative, and the residue thereafter eliminated by treatment with base. As the side-chains were eliminated by these reactions, it is considered that they contain only two sugar residues, which thus excludes two of the three alternative structures. Structure 1 was further confirmed by subjecting SII to a Smith degradation, which yielded the tetrasaccharide L-Rhap-(1 yields 3)-L-Rhap-(1 yields 3)-L-Rhap-(1 yields 2-erythritol, characterised by methylation analysis.     

Structural studies of the O-specific polysaccharide from Plesiomonas shigelloides strain CNCTC 113/92.

The structure of the O-specific side chain of the lipopolysaccharide (LPS) of Plesiomonas shigelloides, strain CNCTC 113/92 has been investigated by NMR spectroscopy, matrix-assisted laser desorption/ionization time of flight mass spectrometry and sugar and methylation analysis. It was concluded that the polysaccharide is composed of a hexasaccharide repeating unit with the following structure: in which D-beta-D-Hepp is Dglycero-beta-Dmanno-heptopyranose and 6d-beta-D-Hep is 6-deoxy-beta-Dmanno-heptopyranose. This structure represents a novel hexasaccharide repeating unit of bacterial O-antigen that is characteristic and unique to the Plesiomonas shigelloides strain. Using the high-resolution magic angle spinning technique, 1H-NMR spectra were also obtained for the O-polysaccharide components of isolated LPS and in their original form directly on the surface of bacterial cells.     

The predatory behavior of Pheidole megacephala

We studied the foraging and predatory behaviors of the invasive African myrmicine ant, Pheidole megacephala (F.) in its native range. Workers can singly capture a wide range of insects, including relatively large prey items. For still larger prey, they recruit at short range those nestmates situated within reach of an alarm pheromone and together spread-eagle the insect. These behaviors are complimented by a long-range recruitment (of nestmates remaining in the nest) based on prey size. P. megacephala scouts also use long-range recruitment when they detect the landmarks of termites and competing ant species, thus permitting them to avoid confronting these termites and ants solitarily.     

Morphological and physiological correlates of the colony foundation mode and reproductive role differentiation in <Emphasis Type="Italic">Belonogaster juncea juncea</Emphasis> (Vespidae,Polistinae)

A study on the reproductive status of Belonogaster juncea juncea individuals was conducted in Cameroon on 21 pre- and 15 post-emergence colonies. We compared the females’ size and ovarian development, and verified if they were inseminated or not. Dominant females were inseminated, had well developed ovaries, and were the largest individuals in pre-emergence colonies; in post-emergence colonies their size did not differ significantly from that of non-dominant females. Most subordinate females of both pre- and post-emergence colonies had thread-like ovaries, but a few had well developed ovaries. In pre-emergence colonies 13 subordinates had thread-like ovaries and several yellow bodies indicating that they had already laid eggs. We deduced that subordinates with well developed ovaries joined the foundations shortly before our study, while those with several yellow bodies had arrived some time before and their ovaries had regressed. At the end of the post-emergence phase appear non-dominant females with well developed ovaries. They are the future foundresses. Some females can disperse just after emergence and join a new foundation without mating. Nevertheless, most co-foundresses were inseminated when they joined the foundations, and so had the potential to reproduce, negating the hypothesis of swarm founding in B. j. juncea. Received 8 November 2006; revised 14 February 2007; accepted 16 February 2007.     

(1)H NMR studies of hydroxy protons of the V[beta-Gal(1-->3)-alpha-GalNAc(1-->O)]THPGY glycopeptide.

The hydroxy protons of the disaccharide moiety in the glycopeptide Val-[beta-Gal(1-->3)-alpha-GalNAc(1-->O)]-Thr-His-Pro-Gly-Tyr (1) have been investigated in aqueous solution using (1)H NMR spectroscopy. The chemical shifts (delta), coupling constants ((3)J(CH,OH)), temperature coefficients (d delta/dT), exchange rates (k(ex)), and NOEs have been measured. The data show that the O(2')H of Gal has a reduced contact with water due to steric interference caused by the 2-acetamido group of GalNAc. No interaction, in terms of hydrogen bonding exists between the disaccharide and the peptide moieties, but the rotation around the sugar-peptide linkage is restricted.     

A DNA-recombinogenic activity in human cells.

A DNA recombining protein has been partly purified from cell lines derived from patients suffering from the hereditary disease, Bloom's syndrome. The protein induces the formation of displacement loops in phi X174 RFI DNA molecules after the addition of single-stranded DNA fragments. A filter binding method and electron microscopy were used to determine the reaction. The recombinogenic protein is dependent on divalent cations and ATP for activity.     

Mapping of the binding specificity for five monoclonal antibodies recognizing 3-deoxy-D-manno-octulosonic acid in bacterial lipopolysaccharides

Mouse mAb were produced against the deep rough strains Salmonella minnesota R 595, Salmonella typhimurium SL 1102, and Escherichia coli D21f2 and screened by enzyme immunoassay against LPS of several chemotypes. Five antibodies were selected for their ability to bind to chemotype deep rough (Re) LPS which has two 3-deoxy-D-manno-octulosonic acid (Kdo) residues in its nonreducing end. Structurally verified oligosaccharides isolated from rough LPS and synthetic analogues of Kdo were used in an enzyme immunoassay inhibition test to determine the binding epitopes for the antibodies. According to their specificities, the antibodies could be divided into three groups. For two of the groups, the recognized structure was the alpha-Kdo (2----4) Kdo disaccharide and for one group the alpha-Kdo (2----4) alpha-Kdo beta-D-GlcN (1----6) alpha-D-GlcN tetrasaccharide, representing a partial structure of the Re LPS. Inhibition studies with synthetic analogues of Kdo showed that the anomeric configuration and the free carboxyl group of the Kdo residue are important features for antibody binding. Changes in the C-1 to C-6 region of the Kdo molecule do influence the antibody recognition considerably whereas changes in the exocyclic C-7 to C-8 region are of secondary importance. Calculation of the conformation of the inner core region showed that the alpha-Kdo (2----4) alpha-Kdo (2---- disaccharide was free and accessible in chemotype Re LPS, but that linkage of a L-glycero-D-manno-heptose to O-5 of the subterminal Kdo both changes the conformation of the Kdo-disaccharide and covers it thereby making it less accessible.     

Structural studies of the Vibrio cholerae o-antigen

The dominant part of the O-antigen of Vibrio cholerae is a homopolysaccharide composed of (1→2)-linked 4-amino-4,6-dideoxy-α-d-mannopyranosyl (perosaminyl) residues, the amino groups of which are acylated by 3-deoxy-l-glycero-tetronic acid. Most of the amino sugar is decomposed during acid hydrolysis. Treatment of the polymer with anhydrous hydrogen fluoride, which cleaves the glycosidic linkages but does not cause N-deacylation, followed by acid hydrolysis under mild conditions, produced the monomer in good yield. Treatment of the N-deacylated polysaccharide with nitrous acid caused deamination with concomitant rearrangements, typical of 4-amino-4-deoxyhexopyranosyl residues in which the amino group occupies an equatorial position.     

Structure of the extracellular polysaccharide from xanthomonas campestris

Xanthan gum, the extracellular polysaccharide from Xanthomonas campestris, has been reinvestigated by methylation analysis, and by uronic acid degradation followed by oxidation and elimination of the oxidized residue. The polysaccharide is composed of pentasaccharide repeating-units with the following structure: