Die Polyuronsäuren der Braunalgen (Kohlenhydrate der Algen I)

Fischer, Franz; Dörfel, Helmut

doi:10.1515/bchm2.1955.302.1-2.186

“…In all titration steps, alginate was added in small volumes so that the increase in sample volume could be neglected. A 15 N-HSQC spectrum was recorded for each titration step, and spectral changes were quantified according to Equation 1.…”

Section: Methodsmentioning

confidence: 99%

NMR Structure of the R-module

Aachmann

¹

,

Svanem

²

,

Güntert

³

et al. 2006

Journal of Biological Chemistry

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In the bacterium Azotobacter vinelandii, a family of seven secreted and calcium-dependent mannuronan C-5 epimerases (AlgE1-7) has been identified. These epimerases are responsible for the epimerization of ␤-D-mannuronic acid to ␣-L-guluronic acid in alginate polymers. The epimerases consist of two types of structural modules, designated A (one or two copies) and R (one to seven copies). The structure of the catalytically active A-module from the smallest epimerase AlgE4 (consisting of AR) has been solved recently. This paper describes the NMR structure of the R-module from AlgE4 and its titration with a substrate analogue and paramagnetic thulium ions. The R-module folds into a right-handed parallel ␤-roll. The overall shape of the R-module is an elongated molecule with a positively charged patch that interacts with the substrate. Titration of the R-module with thulium indicated possible calcium binding sites in the loops formed by the nonarepeat sequences in the N-terminal part of the molecule and the importance of calcium binding for the stability of the R-module. Structure calculations showed that calcium ions can be incorporated in these loops without structural violations and changes. Based on the structure and the electrostatic surface potential of both the A-and R-module from AlgE4, a model for the appearance of the whole protein is proposed.Alginates are unbranched copolymers of 134-linked ␤-D-mannuronic acid (M) 3 and its C-5 epimer ␣-l-guluronic acid (G) (1, 2). Alginates are initially produced as a linear polymer of M-subunits only. Thereafter, single M-subunits in the polymeric chain are converted to G-subunits by enzymes called mannuronan C-5 epimerases. The mechanical and chemical properties of alginates depend on the composition and sequence of the two subunits, in particular, whether they are arranged in MM-, MG-, or GG-blocks. GG-blocks are rigid and form gels with divalent cations such as calcium. Recently, MG-blocks were suggested also to form gels with calcium (3). Poly(M) regions, however, are more flexible without the ability to form gels with cations (4, 5). The relative amounts and distribution of M and G vary extensively among different species of both brown algae (6 -8) and bacteria (9,10) Alginate is for brown algae essentially the same as cellulose is for trees and plants. The stripes of the algae are mainly G-rich, giving them the stiffness to work as a skeleton, whereas leaves are M-rich showing flexibility (11).In Azotobacter sp., alginate is used as a capsular polysaccharide (12, 13), likewise in Pseudomonas sp. (14 -16). In Azotobacter vinelandii, the composition and function of the alginates vary significantly depending on the environmental conditions.Vegetatively growing cells produce alginates that form a loose capsule structure that is easily released into the growth medium. These alginates are typically M-rich (17), but under certain conditions of environmental stress, the cells enter a resting stage designated the "cyst" stage. The cysts are surrounded by a rigid alginate...

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“…The dispersion consists of a liquid phase containing some free amino acids, free ions, sugars, pigments and colloidal polysaccharides such as alginates, laminaran, mannitol, fucoidan and proteins as well as another phase composed of ground leaves and stems. The main polysaccharide in the seaweed extract is alginate (16), which represents between 25-33% of the dry weight of the algae. The extract was obtained by mixing the concentrated paste with distilled water in a 1:1 (v/v) proportion.…”

Section: Marine Brown Algae Extractmentioning

confidence: 99%

“…Alginate is a polysaccharide composed of a binary nonbranched co-polymer from mannuronic (M) and α-L guluronic (G) acids (16,17). These hydrocolloids have the capacity to gel through interaction with carboxylic groups and divalent ions (18,19).…”

Section: Introductionmentioning

confidence: 99%

Influence of cactus mucilage and marine brown algae extract on the compressive strength and durability of concrete

Hernández¹,

Cano-Barrita²,

2016

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This paper presents the mechanical performance and durability of concrete with water/cement (w/c) ratios of 0.30 and 0.60 containing cactus mucilage and brown marine seaweed extract solutions (at 0.5° Brix concentrations). Cylindrical specimens (100 mm×200 mm) were cast and moist-cured for 0 and 28 days. Compressive strength, rapid chloride permeability, and chloride diffusion tests were conducted to evaluate all of the concrete mixes at the ages of 60 and 120 days. In addition, accelerated carbonation tests were carried out on specimens at the age of 180 days by exposure to 23 °C, 60% RH and at 4.4% CO 2 for 120 days. The compressive strength results showed that only one concrete mix with admixtures increased in strength compared to the control. Regarding the rapid chloride permeability, chloride diffusion and carbonation, the results indicated that the durability of concretes containing organic additions was enhanced compared to the control. RESUMEN: Influencia del mucílago de cactus y extracto de algas pardas marinas en la resistencia a compresión y durabilidad del hormigón.Este trabajo presenta el comportamiento mecánico y de durabilidad de concretos con relaciones agua/cemento de 0.30 y 0.60, conteniendo soluciones de mucílago de nopal y extracto de algas marinas cafés (0.5 °Brix de concentración). Especímenes cilíndricos (100 mm×200 mm) fueron elaborados y curados en húmedo por 0 y 28 días. Se evaluó la resistencia a la compresión, permeabilidad rápida y difusión de cloruros a los 60 y 120 días de edad. Adicionalmente, se realizaron pruebas de carbonatación acelerada en especímenes con 180 días de edad, expuestos a 23 °C, 60% HR y 4.4% de CO 2 por 120 días. Los resultados de resistencia a la compresión muestran que únicamente una mezcla de concreto con adición orgánica incrementó su resistencia con respecto al control. Con respecto a la permeabilidad rápida a cloruros, difusión de cloruros y carbonatación, los resultados indican que la durabilidad de los concretos que contenían adiciones orgánicas fue mejorada con respecto al control.

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“…In 1955, FISCHER and D€ oRFEL [177] discovered L-guluronic acid in addition to D-mannuronic acid, and since ca. 1964, alginic acid has been known to be a copolymer of these two residues.…”

Section: Structurementioning

confidence: 99%

Polysaccharides

Voragen

¹

,

Rolin²,

Marr³

et al. 2003

Ullmann's Encyclopedia of Industrial Chemistry

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The article contains sections titled: 1. Introduction 2. Analysis and Characterization 3. Pectin 3.1. Occurrence and Structure 3.2. Pectolytic Enzymes 3.3. Production 3.4. Properties 3.4.1. Physical Properties 3.4.2. Gel Properties 3.4.3. Stability and Chemical Reactions 3.5. Analysis 3.5.1. Measurement and Standardization of Gel‐Forming Capacity 3.5.2. Chemical Analysis 3.6. Pharmaceutical and Nutritional Characteristics 3.7. Application in the Food Industry 3.8. Market 4. Alginates 4.1. Occurrence 4.2. Production 4.3. Structure 4.4. Properties 4.5. Propylene Glycol (Propane‐1,2‐diol) Alginate 4.6. Bacterial Alginates 4.7. Analysis 4.8. Applications 4.9. Market 5. Carrageenan 5.1. Structure 5.2. Sources and Raw Materials 5.3. Production 5.4. Analysis 5.5. Properties 5.6. Applications 5.7. Physiological Properties 6. Agar 6.1. Production 6.2. Structure and Gelling Mechanism 6.3. Quick Soluble Agar 7. Gum Arabic 8. Gum Tragacanth 9. Gum Karaya 10. Gum Ghatti 11. Xanthan Gum 11.1. Production 11.2. Structure and Properties 11.3. Analysis 11.4. Applications, Market 12. Gellan Gum 13. Galactomannans 13.1. Structure 13.2. Production 13.3. Properties 13.4. Analysis and Composition of Commercial Preparations 13.5. Derivatives 13.6. Applications 13.7. Market 14. Acknowledgement

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Die Polyuronsäuren der Braunalgen (Kohlenhydrate der Algen I)

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NMR Structure of the R-module

NMR Structure of the R-module

Influence of cactus mucilage and marine brown algae extract on the compressive strength and durability of concrete

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