Evaluation of Structure and Assembly of Xyloglucan from Tamarind Seed (Tamarindus indica L.) with Atomic Force Microscopy

Abstract

The role of xyloglucan (XG) in the cell wall of plants and its technological usability depends on several factors, pertaining to molecular structure. Therefore, the goal of this study was to evaluate the nano-structure and self-assembly of XG by atomic force microscopy (AFM). As the model, a non-modified xyloglucan from a tamarind seed (Tamarindus indica L.) was used. Samples were minimally processed, i.e., treated with low-power ultrasound and studied on the surface of mica in ambient butanol. AFM topographic images revealed rod-like nanomolecules of xyloglucan with a mean height of 2.3 ± 0.5 nm and mean length of 640 ± 360 nm. The AFM study also showed that XG chains possessed a helical structure with a period of 115.8 ± 29.2 nm. This study showed possible-bending of molecules with a mean angle of 127.8 ± 25.6°. The xyloglucan molecules were able to aggregate as cross-like and a parallel like assemblies, and possibly as rope-like structures. The self-assembled bundles of xyloglucan chains were often complexed at an angle of 114.2 ± 36.3°.

Xyloglucan in the primary cell wall: assessment by FESEM, selective enzyme digestions and nanogold affinity tags

“…We therefore expected it to have the form of ~100‐nm wide random coils with the chain direction becoming randomized along 8‐nm segments. However, xyloglucan also aggregates in solution (Gidley et al ., ; Lang and Burchard, ; Freitas et al ., ; Lopez et al ., ; Muller et al ., ) and can form stiff rod‐like aggregates under some conditions (Koziol et al ., ).…”

“…The finding that xyloglucan in the cell wall can be stained with iodine (Hayashi and Maclachlan, ) suggests that a portion may be in a highly solvated form (required for iodine intercalation), a conclusion also supported by xyloglucanase digestions (Pauly et al ., ; Park and Cosgrove, ), mechanical studies of pectin mutants (Abasolo et al ., ) and ssNMR studies of spin diffusion between xyloglucan and pectin (White et al ., ; Wang and Hong, ). In contrast, when tamarind xyloglucan was dried onto mica surfaces it assumed extended, highly aggregated, helical conformations (Koziol et al ., ) that differ markedly from its solution state and from its proposed conformation in muro . Other studies have also noted xyloglucan's innate propensity to aggregate (Gidley et al ., ; Lang and Burchard, ; Freitas et al ., ; Muller et al ., ).…”

Functional properties and physicochemical characteristics of tamarind ( Tamarindus indica L.) seed mucilage powder as a novel hydrocolloid

“…Peaks at 1370, 1150, 1037, 1071, 944 and 987 cm À1 are characteristics of xyloglucan (Kozioł et al, 2015;Szymanska-Chargot and Zdunek, 2013), which is an important component of tamarind seed mucilage particles. Band at 1370 cm À1 denotes the CH 2 bending of xyloglucan, the soft peak at 1150 cm À1 corresponds to O-C-O asymmetric stretching, meanwhile peaks at 1037 and 1071 cm À1 are result of C-O and C-C stretching of xyloglucan ring, band at 944 cm À1 corresponds to ring vibration of xyloglucan and finally, 897 cm À1 band is due to C-H stretching characteristic of glucose and xylose b-anomeric links (Kozioł et al, 2015;Munir et al, 2016;Szymanska-Chargot and Zdunek, 2013).…”

Revision of adsorption models of xyloglucan on microcrystalline cellulose

“…Additionally, it has short side chains of xylose, galactose and often but not always a terminal fucose or arabinose, which prevent the assembly of xyloglucan into a crystalline cellulose-like microfibl. Tamarind xyloglucan is an example of non-fucosylated storage xyloglucan (Zykwinska et al 2008;Kozioł et al 2015), and its molar mass is estimated at 763 kDa (Zykwinska et al 2005). The conformation may partially resemble a flat ribbon, which is thought to be able to create hydrogen bond to the similar bglucan chains of cellulose on the surface of the microfibril (Albersheim et al 2011).…”