Nascent pectin and glucuronoxylan were prepared from membrane-bound enzymes obtained from pea epicotyls. They had previously been shown to exhibit a protein- and pH-dependent pattern of binding to cell wall ghosts and...Nascent pectin and glucuronoxylan were prepared from membrane-bound enzymes obtained from pea epicotyls. They had previously been shown to exhibit a protein- and pH-dependent pattern of binding to cell wall ghosts and to xy-loglucan extracted from cell walls prepared from pea epicotyls;maximum binding required a pH of 3-4, and the pres-ence of cell wall proteins, namely assemblins. To determine whether wall polysaccharides deposited in cell walls be-have in the same manner as nascent polymers, radioactively labeled EDTA-soluble polymers were prepared from newly-deposited pea epicotyl cell walls. Different enzyme treatments followed by column chromatography, in addition to complete acid hydrolysis followed by paper and thin layer chromatography, indicated the presence of pectin, to-gether with smaller amounts of glucuronoxylan, in this EDTA-soluble extract. These radioactively labeled polysaccha-rides were found to bind to cell wall ghosts and to xyloglucan extracted from the second and third internodes of pea epicotyls cell walls in a pH-dependent manner, similar to the binding pattern obtained with nascent polymers. Maxi-mum binding occurred at pH 3-4, and also required the presence of protein.展开更多
Germinating seeds of Tamarindus indica contain endo-β-1, 4-xyloglucanases which degrade tamarind xyloglucan, but not carboxymethylcellulose (CMC). The xyloglucanases are isolated from the germinating tamarind seeds u...Germinating seeds of Tamarindus indica contain endo-β-1, 4-xyloglucanases which degrade tamarind xyloglucan, but not carboxymethylcellulose (CMC). The xyloglucanases are isolated from the germinating tamarind seeds using 50 mM acetate buffer, pH 5.5 containing 0.5 M NaCl. The Km value is 0.667 g/liter and the enzyme is optimally active at pH 5.5 and stable between pH 4 - 6.5. The optimum temperature is 45?C and is quite stable upto 50?C. The activity declined by 50% at 60?C and is completely inactivated at 70?C. Highest xyloglucanase activity and specific activity are observed on the 23rd day of germination. The polyacrylamide gel electrophoresis (PAGE) indicated the presence of five isozymes of xyloglucanases which are visualized by activity staining separately with congo red and grams iodine. Isozyme 2 is the major xyloglucanase present throughout the germination period.展开更多
Plant components are an inexhaustible source for the construction of bio-based materials.Here we report,for the first time,the elaboration of biobased cellulose nanocrystals(CNC)/xyloglucan(XG)hydrogels.XG is a hemice...Plant components are an inexhaustible source for the construction of bio-based materials.Here we report,for the first time,the elaboration of biobased cellulose nanocrystals(CNC)/xyloglucan(XG)hydrogels.XG is a hemicellulose displaying a great affinity for cellulose surface and can be thus irreversibly adsorbed on CNC.Properties of the hydrogels were investigated by varying the molar mass of XG either by enzymatic treatment with Endo-glucanase(EG2)or physical fractionation by ultrasound(US).Fractions were characterised by high-performance size exclusion chromatography(HPSEC)and their monosacchari decompositions were determined.Three fractions with high,average and small molar mass,(800,300 and 100103 g/mol respectively),were selected in order to tune the properties of the hydrogel.Sol-gel transition conditions were determined for each fraction by achieving phase diagram using the inverted tube method.Mechanical properties,assessed by rheology,are improved by increasing XG molar mass since elastic modulus is higher for hydrogels formed with higher molar mass fractions as well as the strain at break.Gel formation is likely due to the adsorption of XG fractions on CNC which increases the effective hydrodynamic volume of CNC leading to steric stabilization and interactions between loops and tails of XG adsorbed.展开更多
文摘Nascent pectin and glucuronoxylan were prepared from membrane-bound enzymes obtained from pea epicotyls. They had previously been shown to exhibit a protein- and pH-dependent pattern of binding to cell wall ghosts and to xy-loglucan extracted from cell walls prepared from pea epicotyls;maximum binding required a pH of 3-4, and the pres-ence of cell wall proteins, namely assemblins. To determine whether wall polysaccharides deposited in cell walls be-have in the same manner as nascent polymers, radioactively labeled EDTA-soluble polymers were prepared from newly-deposited pea epicotyl cell walls. Different enzyme treatments followed by column chromatography, in addition to complete acid hydrolysis followed by paper and thin layer chromatography, indicated the presence of pectin, to-gether with smaller amounts of glucuronoxylan, in this EDTA-soluble extract. These radioactively labeled polysaccha-rides were found to bind to cell wall ghosts and to xyloglucan extracted from the second and third internodes of pea epicotyls cell walls in a pH-dependent manner, similar to the binding pattern obtained with nascent polymers. Maxi-mum binding occurred at pH 3-4, and also required the presence of protein.
文摘Germinating seeds of Tamarindus indica contain endo-β-1, 4-xyloglucanases which degrade tamarind xyloglucan, but not carboxymethylcellulose (CMC). The xyloglucanases are isolated from the germinating tamarind seeds using 50 mM acetate buffer, pH 5.5 containing 0.5 M NaCl. The Km value is 0.667 g/liter and the enzyme is optimally active at pH 5.5 and stable between pH 4 - 6.5. The optimum temperature is 45?C and is quite stable upto 50?C. The activity declined by 50% at 60?C and is completely inactivated at 70?C. Highest xyloglucanase activity and specific activity are observed on the 23rd day of germination. The polyacrylamide gel electrophoresis (PAGE) indicated the presence of five isozymes of xyloglucanases which are visualized by activity staining separately with congo red and grams iodine. Isozyme 2 is the major xyloglucanase present throughout the germination period.
文摘Plant components are an inexhaustible source for the construction of bio-based materials.Here we report,for the first time,the elaboration of biobased cellulose nanocrystals(CNC)/xyloglucan(XG)hydrogels.XG is a hemicellulose displaying a great affinity for cellulose surface and can be thus irreversibly adsorbed on CNC.Properties of the hydrogels were investigated by varying the molar mass of XG either by enzymatic treatment with Endo-glucanase(EG2)or physical fractionation by ultrasound(US).Fractions were characterised by high-performance size exclusion chromatography(HPSEC)and their monosacchari decompositions were determined.Three fractions with high,average and small molar mass,(800,300 and 100103 g/mol respectively),were selected in order to tune the properties of the hydrogel.Sol-gel transition conditions were determined for each fraction by achieving phase diagram using the inverted tube method.Mechanical properties,assessed by rheology,are improved by increasing XG molar mass since elastic modulus is higher for hydrogels formed with higher molar mass fractions as well as the strain at break.Gel formation is likely due to the adsorption of XG fractions on CNC which increases the effective hydrodynamic volume of CNC leading to steric stabilization and interactions between loops and tails of XG adsorbed.
