Sulfate substituents naturally occurring in biomolecules, such as oligosaccharides and polysaccharides, can play a critical role in major physiological functions in plants and animals. We show that laminarin, a b-1,3 glucan with elicitor activity in tobacco (Nicotiana tabacum), becomes, after chemical sulfation, an inducer of the salicylic acid (SA) signaling pathway in tobacco and Arabidopsis thaliana. In tobacco cell suspensions, the oxidative burst induced by the laminarin sulfate PS3 was Ca 2þ dependent but partially kinase independent, whereas laminarin triggered a strickly kinase-dependent oxidative burst. Cells treated with PS3 or laminarin remained fully responsive to a second application of laminarin or PS3, respectively, suggesting two distinct perception systems. In tobacco leaves, PS3, but not laminarin, caused electrolyte leakage and triggered scopoletin and SA accumulation. Expression of different families of Pathogenesis-Related (PR) proteins was analyzed in wild-type and mutant tobacco as well as in Arabidopsis. Laminarin induced expression of ethylene-dependent PR proteins, whereas PS3 triggered expression of ethylene-and SA-dependent PR proteins. In Arabidopsis, PS3-induced PR1 expression was also NPR1 (for nonexpressor of PR genes1) dependent. Structure-activity analysis revealed that (1) a minimum chain length is essential for biological activity of unsulfated as well as sulfated laminarin, (2) the sulfate residues are essential and cannot be replaced by other anionic groups, and (3) moderately sulfated b-1,3 glucans are active. In tobacco, PS3 and curdlan sulfate induced immunity against Tobacco mosaic virus infection, whereas laminarin induced only a weak resistance. The results open new routes to work out new molecules suitable for crop protection.
SummaryHAT is the most frequent drug induced immune-thrombocytopenia. We recently identified multimolecular PF4/heparin complexes as the major antigen. In order to evaluate the structural requirements for formation of the antigenic complex, we chemically synthesized 13 glucan sulfates and used 5 heparin fractions (2.4-4.8 kD) and a synthesized pentasaccharide, representing the antithrombin III binding sequence of heparin, to further characterize the HAT antigen. In the presence of glucan sulfates and heparin, HAT antibodies caused platelet activation typically at low but not at high concentrations, as measured by 14C-5HT release. The concentration range giving the activation pattern depended on the degree of sulfation (DS) and molecular weight (MW) of the glucan sulfates but not on the type of glycosidic linkage of a polysaccharide. With linear glucan sulfates with a chain length of 35 monosaccharides, the critical DS to form the HAT antigen ranged between 0.60 and 1.20. Glycosidic branched glucan sulfates were able to form the HAT antigen at a lower DS and a lower MW than linear glucan sulfates. Platelet activation by HAT-antibodies in the presence of linear curdlan sulfate fractions was dependent on their MW. At a low concentration (0.01 µM) medium-size fractions (60 kD) caused platelet activation but neither small (12 kD) nor large fractions (>150 kD) did. At higher concentrations (2 µM) the opposite reaction pattern was observed. In the case of heparin, the optimal chain length for forming the HAT antigen is a hexadecasaccharide (4.8 kD). Antigen generation decreased with larger and smaller fractions. For 50% platelet activation by HAT antibodies increasing concentrations of heparin were necessary using heparins with decreasing MW: 0.02 ± 0.015 µM (4.8 kD), 0.09 ± 0.016 pM (3.0 kD), 0.8 ± 0.21 µM (2.4 kD). In the presence of the pentasaccharide, HAT antibodies did not cause platelet activation atany concentration tested, nor bound to PF4-pentasaccha- ride complexes in a PF4 based ELISA system. We conclude that generation of the HAT antigen is dependent on the ratio of MW and DS of a glucan sulfate. We conclude from this study that a carbohydrate based anticoagulant with a reduced risk of forming the HAT antigen should be linear with a DS<0.6 or a MW <2.4 kD. These data might be important for the design of new drugs for parenteral anticoagulation.
The dependence of gas temperature on gas flow through a direct current, slot-type, atmospheric pressure microplasma in helium or argon was investigated by a combination of experiments and modelling. Spatially resolved gas temperature profiles across the gap between the two electrodes were obtained from rotational analysis of N 2 (C 3 u → B 3 g) emission spectra, with small amounts of N 2 added as actinometer gas. In Ar/N 2 discharges, the N 2 (C 3 u v = 0 → B 3 g v = 0) emission spectra were fitted with a two-temperature population distribution of the N 2 (C) state, and the gas temperature was obtained from the 'low temperature' component of the distribution. Under the same input power of 20 kW cm −3 , the peak gas temperature in helium (∼650 K) was significantly lower than that in argon (over 1200 K). This reflects the much higher thermal conductivity of helium gas. The gas temperature decreased with increasing gas flow rate, more so in argon compared with helium. This was consistent with the fact that conductive heat losses dominate in helium microplasmas, while convective heat losses play a major role in argon microplasmas. A plasma-gas flow simulation of the microdischarge, including a chemistry set, a compressible Navier-Stokes (and mass continuity) equation and a convective heat transport equation, was also performed. Experimental measurements were in good agreement with simulation predictions.
High content of Polysaccharide Hydrocolloids Low content of Polysaccharide Hydrocolloids Althaea officinalis Ti/ia cordata Plantagopsyllium Ti/ia platyphyllos Plantago md/ca Verbascum sp. Plantago ovata Toss//ago farfara Linum us/f atissimum Ma/va si/vest ris Lichen islandicus Plantago lanceolata Symphitum officinalis Chamornilla recutita The polysaccharides actually used for pharmaceutical purposes can be devided in two groups: the natural and the modified natural hydrocolloids (Table 2). The susceptibility of polysaccharides to a broad range of chemical and enzymatic transformations provides additional opportunities for the extension of their utility. Countless methods are being used and developed for polysaccharide modifications resulting in the development of new useful derivatives (3). The importance of various polysaccharide hydrocolloids for pharmaceutical purposes has a long historical background and increased considerably during the last decades (Table 3). This is not only the case for polysaccharides used as excipients essential for specific drug formulations, but also for a series of carbohydrate polymers which have proven to be most useful as physiologically active drugs (4). Many in
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.