Crystalline Structures of Alginic Acids

Atkins, E. D. T.; Mackie, William; Smolko, Eduardo E.

doi:10.1038/225626a0

Cited by 104 publications

(39 citation statements)

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“…A D-mannuronate prefers a 3-fold left-handed helix with weak intra-molecular hydrogen bonding between the 3-OH group and the ring oxygen of the adjacent residue of the nonreducing side, whereas a L-guluronate forms stiffer 2-fold screw helical chains through intramolecular hydrogen bonding between the carboxyl group and the 2-OH of the reducing side [31][32][33]. This influences the extent of cross ring fragmentations 2,5 A red and 0,4 A red .…”

Section: Discussionmentioning

confidence: 99%

Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray tandem mass spectrometry

Zhang

Zhao

et al. 2006

J. Am. Soc. Mass Spectrom.

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Negative-ion electrospray tandem mass spectrometry (ES-MS/MS) with collision-induced dissociation (CID) is attempted for sequence determination of alginate oligosaccharides, derived from polyanionic alginic acid, polymannuronate, and polyguluronate by partial depolymerization using either alginate lyase or mild acid hydrolysis. Sixteen homo-and hetero-oligomeric fragments were obtained after fractionation by gel-filtration and strong anion exchange high performance liquid chromatography. The product-ion spectra of these alginate oligosaccharides were dominated by intense B-, C-, Y-, and Z-type ions together with 0,2 A-and 2,5 A-ions of lower intensities. Internal mannuronate residues (M) produce weak but specific decarboxylated Z int -ions (Z int Ϫ 44 Da; int: denotes internal), which can be used for distinction of M and a guluronate residue (G) at an internal position. A reducing terminal M or G, although neither gives rise to a specific ion, can be identified by differences in the intensity ratio of fragment ions of the reducing terminal residue [ [2,3]. Infection with the latter opportunistic pathogen seen in cystic fibrosis patients remains a major health concern [4]. Alginate consists of hexuronic acid residues ␤-Dmannuronic acid (M) and ␣-L-guluronic acid (G) with exclusively 1¡4 glycosidic linkages. Along its linear chain, there are homo-oligomeric regions of mannuronate (M-blocks) and of guluronate (G-blocks) as well as hetero-oligomeric regions (MG-blocks) [5,6]. In contrast to algal alginate and alginate of A. vinelandii, the absence of G-blocks or low ratio of G-to M-blocks is characteristic for alginate from most bacteria such as P. aeruginosa. The alginate coat of P. aeruginosa is known to provide protection from immune defence system. Oligomannuronates have been shown to have an inhibitory effect on reactive oxidizing species production [7] from immune cells, whereas oligoguluronates with similar sizes did not exhibit any significant effect [8]. The physical properties of the alginates have also been well documented and can be used as thermally stable cold setting gelling agents in the presence of calcium ions, gelling at far lower concentrations than gelatin. High G content produces strong, brittle gels with good heat stability whereas high M content produces weaker, more-elastic gels with good freeze-thaw behavior. Alginate oligosaccharide fragments and their derivatives have been widely used as releasing agents in the pharmacy [9], as additives in the food industry [10], and as growth-promoters in agriculture [11]. Recently, it has also found important applications in tissue engineering [12].Polyanionic oligosaccharides such as those derived from glycosaminoglycans have attracted considerable interests recently because of the increased awareness of their functional properties. The functional properties of alginates and their oligosaccharide fragments are intimately linked to the composition (M/G ratio) and sequences of the hexuronic acid M and G residues. Methods for identification of oligosacc...

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Section: Discussionmentioning

confidence: 99%

Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray tandem mass spectrometry

Zhang

Zhao

et al. 2006

J. Am. Soc. Mass Spectrom.

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“…For instance sodium pectate has hexagonal symmetry, with a = 1.62nm and c (fibre axis) = 1.31nm (Palmer & Hertzog, 1945). The two component polyuronic acids ofalginic acid crystallize in orthorhombic unit cells (Atkins et al, 1970 giving goodquality X-ray 'fibre' diffraction patterns. The sulphated polysaccharide seaweed K-and &-carrageenans, more similar to the mucopolysaccharides with their [-A-B-], repeat, crystallize in the form of double-stranded helices (Anderson et al, 1969).…”

Section: X-ray-diffraction Patternsmentioning

confidence: 99%

“…The (1 eq,4eq)-linked polyuronic acids (Atkins et al, 1970) distribute their carboxylate groups equally on either side of the chain in the twofold helix, and any untwisting from this position distributes such groups more evenly over the surface of a cylinder. We consider that this is a requirement for the formation of linear polyelectrolytes.…”

Section: Polyelectrolyte Behaviourmentioning

confidence: 99%

The conformation of the mucopolysaccharides. Hyaluronates

Atkins

Phelps

Sheehan

1972

Biochemical Journal

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123

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X-ray-diffraction patterns of hyaluronate fibres from a variety of sources were obtained. Sodium hyaluronate gives well-defined patterns which index on a hexagonal unit cell with dimensions a 1.17±0.01nm and a fibre repeat-distance of 2.85 ±0.03nm. A further form of sodium hyaluronate is produced by annealing at 60°C in 75 % relative humidity. This stable state indexes on a hexagonal unit cell of unchanged fibre repeatdistance but with a = 1.87nm. The chain conformation is a threefold helix. Analysis of these diffraction patterns led to two tentative structures for sodium hyaluronate, involving different packing of the polysaccharide chains. The significance of side-chain interaction is discussed. Hyaluronic acid produces an X-ray pattern different from that obtained with the sodium salt. The fibre repeat-distance is 1.96±0.02nm and the unit cell appears to be monoclinic. The chain conformation is a twofold helix and conformational change between free acid and monovalent salt is discussed. These findings, together with model-building experiments, are interpreted as indicating a highly ordered structure, and the physical properties of hyaluronate solutions with regard to molecular shape and polyelectrolyte behaviour are rationalized.

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“…El descubrimiento de la presencia en el ácido algínico de residuos de ácido L-gulurónico, además de D-manurónico, ha hecho necesario revisar la definición de dicho ácido (35). Actualmente se sabe que el ácido algínico se forma a partir del ácido β-D-manurónico (M) o de su epímero C-5, el ácido α-Lgulurónico (G), monómeros que se unen para formar largas moléculas lineales con enlaces glicosídicos (1→4) (36), dando lugar a la estructura secundaria (37), ilustrada en la figura 1. La secuencia de ambos ácidos es variable, y depende del alga utilizada, de la parte del alga empleada para su fabricación y de la vejez de las algas (38), ya que las epimerasas que realizan esta transformación (de M a G) son enzimas que se presentan sobre todo en las algas de mayor edad, lo que significa que en las algas más maduras el contenido en grupos G es mayor que en algas más jóvenes, lo que repercutirá en su poder gelificante.…”

Section: Estructura Y Propiedades De Los Alginatosunclassified

Nuevas aplicaciones de los alginatos en el conformado cerámico

Santacruz¹,

Nieto²,

Moreno³

2005

Bol. Soc. Esp. Ceram. Vidr.

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Los alginatos son polisacáridos naturales empleados a menudo en el procesamiento cerámico como ligantes temporales. Sin embargo, además de su función espesante, los alginatos presentan interesantes propiedades como agente gelificante. Esta función ha sido menos explotada en cerámica pero está empezando a recibir gran atención por su versatilidad de cara a nuevas rutas de conformado de piezas y, sobre todo, de láminas y recubrimientos. En este trabajo se revisan los procesos de conformado neto (near-net shaping, NNS) por formación de geles químicos, entre los que se pueden distinguir dos grupos de técnicas, las que emplean monómeros que polimerizan en presencia de un activador y/o catalizador y las que emplean polisacáridos de elevado peso molecular que forman estructuras a través de cationes presentes en el medio. Este trabajo se centra en el último caso y, en particular, se revisa la química de los alginatos, haciendo énfasis en su estructura y en los mecanismos de gelificación y, por último, se evalúan las posibilidades de aplicación de la gelificación química con alginatos en la producción de láminas por la técnica de colaje en cinta, con especial atención a los parámetros que gobiernan el proceso. Palabras clave: Procesamiento, Conformado, Suspensiones, Aditivos de procesamiento, Gelificación química, Alginatos New applications of alginates in the shape forming of ceramicsAlginates are naturally occurring polysaccharides frequently used as temporary binders in ceramic processing. However, behind their thickenning behaviour, alginates have interesting gelling properties. This function has not been exploited in ceramics, although it is receiving increased attention because of the versatility facing new shaping routes for manufacturing bulk pieces and, in particular, films and coatings. This work reviews the near-net shaping of ceramics through chemical gelation, among which two groups of techniques can be distinguished: those using monomers that polymerize by means of initiators/catalysts, and those using high molecular weight polysaccharides that develop a network structure by means of cations present in the medium. The last case is reviewed in this work, which presents the basis of the chemistry of alginates, focusing their structure and the gelation mechanism, and explores the viability of alginate gelation in the manufacture of thick films by tape casting on the basis of the processing parameters. Key words: Processing, Shaping, Suspensions, Processing additives, Chemical gelation, Alginates INTRODUCCIÓNLos costes totales de producción y el impacto medioambiental son aspectos determinantes para la implantación de un proceso de conformado. El procesamiento coloidal permite obtener piezas de forma compleja con un elevado control del número y tamaño de defectos, así como una alta reproducibilidad y fiabilidad (1,2,3). Por estas razones, se está realizando un gran esfuerzo en el desarrollo de nuevos métodos de conformado coloidal más versátiles y rentables (2,3). Una vía importante en este aspecto, es la fabri...

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Crystalline Structures of Alginic Acids

Cited by 104 publications

References 6 publications

Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray tandem mass spectrometry

Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray tandem mass spectrometry

The conformation of the mucopolysaccharides. Hyaluronates

Nuevas aplicaciones de los alginatos en el conformado cerámico

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