Characterisation of Ca– and Al–pectate gels by thermal analysis and FT-IR spectroscopy

Mimmo, Tanja; Marzadori, Claudio; Montecchio, Daniela; Gessa, C.

doi:10.1016/j.carres.2005.08.011

Cited by 56 publications

(34 citation statements)

References 33 publications

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“…The thermal profiles of the Ca-Al-PG networks seemed even more regular than the Ca-PG networks. This might be explained by the fact that Al concentrations as 100 μM used in this experiments do not disrupt the structure of the network as was described by Mimmo et al (2005) for higher Al concentrations. As previously observed, the Δm of the first exothermic peak decreases passing from DE 0% to DE 65%.…”

Section: Metal Desorptionmentioning

confidence: 83%

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Does the degree of pectin esterification influence aluminium sorption by the root apoplast?

2008

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This study investigates the influence of the degree of pectin esterification (DE) on the sorption of aluminium (Al) by plant roots. Ca-pectates, with varying degrees of esterification, are major constituents of the soil-root interface and of the root apoplast. Capectate networks (Ca-PG and Ca-Al-PG) were formed at three DEs (0%, 26%, 65%) with custom-made cells and used as a model system for the root cell wall. Sorption of Al was conducted for 24 h at a range of oxalic acid concentrations (0-500 μM) at pH 4.50 to examine two different metal resistance mechanisms of plants. In fact, plants release organic acids either to desorb or to complex metals to prevent their sorption by plant roots.Thermal analysis showed that Al sorption did not seem to affect the stability of the pectate gels and the presence of hydrophobic groups (-CH 3 ) at DE>0% seemed to even increase the stability of the gels decreasing thermal decomposition. Results suggest two potential Al tolerance mechanisms: (a) high oxalic acid concentrations (500 μM) were able to desorb almost 100% and 72% at DE 65 and 0%, respectively;(b) high oxalic acid concentrations (500 μM) and thus molar ratios of 5:1 (oxalate/Al) reduced Al sorption by 98% and 86% at DE 65 and 0%, respectively. In conclusion, both mechanisms indicate that high degrees of esterification as 65% are much more efficient in excluding Al from the apoplast and might therefore contribute to Al resistance in plants.

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Section: Metal Desorptionmentioning

confidence: 83%

“…The maxima of the first two peaks were slightly different than the one found in earlier studies ). In the present experiment a PGA with a purity of 85% was used whereas Mimmo et al (2005) used a PGA with a purity of 98%. This difference might explain the shift of the exothermic peaks.…”

Section: Metal Desorptionmentioning

confidence: 99%

Does the degree of pectin esterification influence aluminium sorption by the root apoplast?

2008

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“…3 we can see the thermograms of alginate and chitosan which show initial endothermic peaks at 86.6 and 62.0°C and higher exothermic peaks at 247.8 and 311.0°C, respectively. Endothermic peaks are correlated with loss of water associated to hydrophilic groups of polymers while exothermic peaks resulted from degradation of polyelectrolytes due to dehydration and depolymerization reactions most probably to the parcial decarboxilation of the protonated carboxylic groups and oxidation reactions of the polyelectrolytes (Mimmo, Marzadori, Montecchio, & Gessa, 2005;Soares, Santos, Chierice, & Cavalheiro, 2004;Zohuriaan & Shokrolahi, 2004). Thermogram of alginate/chitosan physical mixture show a broader endothermic peak at 76.7°C, which probably represents the coalescence of both isolated endothermic polymer peaks and exothermic peaks at 250.4 and 309.6°C resulted from individual contribution of alginate and chitosan, respectively.…”

Section: Resultsmentioning

confidence: 99%

Characterization of insulin-loaded alginate nanoparticles produced by ionotropic pre-gelation through DSC and FTIR studies

Sarmento

Ferreira

Veiga

et al. 2006

Carbohydrate Polymers

458

218

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Insulin-loaded nanoparticles were prepared by ionotropic pre-gelation of alginate with calcium chloride followed by complexation between alginate and chitosan. The influence of the pH and stoichiometry relationship between polyelectrolytes providing individual particles with a nano-scale size was assessed by photon correlation spectroscopy (PCS) and scanning electron microscopy (SEM). Insulinpolyelectrolyte interactions at varying pH and polyelectrolytes stoichiometry were assessed by differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR) studies. Individual and smaller sizing nanoparticles, around 800 nm, were obtained at pH 4.7 with an alginate:chitosan mass ratio of 6:1. Thermograms of insulin-loaded nanoparticles originated shifts on same unloaded nanoparticle peaks and suggested polyelectrolytes-protein interactions at pH around 4.5-5.0. FTIR spectra of insulin-loaded nanoparticles showed amide absorption bands characteristic of protein spectra and revealed the formation of new chemical entities.

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“…Aluminium has been shown to bind in excess of charges available due to hydrolysis. 20 Mimmo et al, 21 using FT-IR showed that Al sorption on Ca-pectate gels weakens the gel structure, due to reorganisation of chain aggregates. Fuks et al 22 demonstrated that La co-ordination with pectin involves two uronic acid anions each binding through C(6) and C(6 0 ) carboxyl oxygen atoms and C(5) ring oxygen atom as well as several water molecules.…”

Section: Effect Of Type Of Cation and Concentration On Gel Strengthmentioning

confidence: 98%

Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls

McKenna

Nicholson

Wehr

et al. 2010

Carbohydrate Research

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Characterisation of Ca– and Al–pectate gels by thermal analysis and FT-IR spectroscopy

Cited by 56 publications

References 33 publications

Does the degree of pectin esterification influence aluminium sorption by the root apoplast?

Does the degree of pectin esterification influence aluminium sorption by the root apoplast?

Characterization of insulin-loaded alginate nanoparticles produced by ionotropic pre-gelation through DSC and FTIR studies

Effects of Ca, Cu, Al and La on pectin gel strength: implications for plant cell walls

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