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This paper concerns the 13C NMR signal assignment in the DMSO of a neutral polysaccharide, scleroglucan. The previously proposed chemical structure is confirmed. The 13C NMR spectrum shows that scleroglucan is a regular poly (A, B, C, D) type glucan. The relaxation times of the different series of carbon atoms demonstrate that a single, pendant glucose group is attached to each third monomer along the main chain of what is a β(1 → 3)-glucan. Partial acid hydrolysis gives a spectrum analogous to that of the β(1 → 3)-d-glucan, curdlan, and confirms the structure of the polymer backbone.In aqueous solution, no signal has been obtained due to the existence of a rigid, ordered conformation as demonstrated by optical rotation; in the presence of sodium hydroxide, a conformational transition is produced just as with curdlan. The conclusion is that the behaviour of scleroglucan in solution is similar to that of other β(1 → 3)-d-glucans even though it is more soluble. 相似文献
94.
Several new peracetylated pyrimidine N-1 nucleosides containing one or two β-d-hexopyranosyl residues have been synthesized and their physical characteristics are reported. The conformation of these nucleosides has been investigated by high-resolution 13C-n.m.r. analysis after deblocking. It was possible to distinguish between the syn and anti rotamers of 3-β-d-glucopyranosyluracil, and to establish the favored anti conformation in solution of the nucleoside disaccharide, antibiotic anthelmycin. 相似文献
95.
Michel Lagarde Marc Dechavanne Michel Rigaud Jacqueline Durand 《Prostaglandins & other lipid mediators》1979,17(5):685-705
Radioimmunoassays of platelet prostaglandins E1 and F1α in platelet rich plasma or platelet suspension, demonstrate that both PGE1 and PGF1α are present at higher concentrations than prostaglandins E2 and F2α. Gas chromatography — mass spectrometry determinations of prostaglandins E1 and E2 in resting washed platelets confirm this difference. Lastly, there is a greater incorporation of [1-14C] acetate into prostaglandins E1 and F1α compared to that into prostaglandins E2 and F2α. 相似文献
96.
When single mast cells were isolated by micromanipulation, specific H-2 antigen-bearing mast cells were degranulated upon incubation with alloimmune sera (DAAD). When specific alloantigens were presented by lymphoid cells only, no degranulation occurred. Only antigen-bearing mast cells were degranulated, irrespectively of the presence of antigen-bearing lymphoid cells. Therefore, in DAAD, anaphylactic alloantibodies can and must recognize specific H-2 antigens on the mast cell membrane and simultaneously deliver the degranulation signal, through an Fc-Fc receptor interaction on the surface of the same mast cell. 相似文献
97.
Comparisons were made between the efficacy of naloxone to reverse analgesia induced by electrical stimulation (SPA) of the periaqueductal gray matter and analgesia induced by microinjections of morphine into the same brain region. Naloxone at 1 or 10 mg/kg was ineffective in antagonizing SPA during the first two minutes post-stimulation. Although some antagonism did appear 3–5 minutes after stimulation, the effect was neither consistent nor dose-dependent. Morphine, on the other hand, was antagonized in a dose-dependent and complete fashion by naloxone. The assumption that similar mechanisms underlie both opiate and electrical stimulation induced analgesia is discussed. 相似文献
98.
The photocurrent in photosensitive bilayer lipid membranes has been studied as a function of the aqueous acceptor. Correlations are observed between the relative photocurrent and the position of the complex ion visible absorption band and the dipole moment of the ligand. The effect of the ligands is nondirectional: they may be added to either side of the membrane with a corresponding effect on the photocurrent. The effects of the ligands are interpreted using an energy barrier model. 相似文献
99.
100.
The effect of p-chlorophenylalanie (p-CPA) --300 mg/kg-- on reproduction has been studied in the female rat. Groups of animals were injected with a dose of 300 mg/kg of p-CPA 48 hours before proper copulation conditions at different moments along the ovarian cycle. Presence of spermatozoa in the vaginal frotis was negative in treated rats; in the control groups however, positivity was found in variable proportions according to the phase of the ovarian cycle: 30 ad 90% in diestrus and proestrus respectively. Treated animals showed continuous diestrus phases and diffuse luteinitation of the ovary. The results may indicate that a decrease of cerebral 5-HT, caused by p-CPA, lessens the reproductive behaviour of the female rat through mechanisms depending probably on the liberation of gonadrotrophins. 相似文献