Direct imaging of polysaccharides using at. force microscopy (AFM) or transmission electron microscopy (EM) are important alternatives to phys. characterization of non-cryst. biopolymers in soln. Contrast, resoln. and artifacts connected either with specimen prepn. or imaging are all crit. issues related to the application of EM and AFM on noncryst. biopolymers. These techniques may provide information about polymer configuration, structural information (mass per unit length, ML), conformational transitions, polymer topol., chain assocns., and functional properties. The potential of these techniques applied to polysaccharides were illustrated by imaging the scleroglucan triple-helical structure in its unmodified form, the aldehyde and carboxylated derivs. of scleroglucan, scleraldehyde and sclerox, resp., and gel precursors of scleraldehyde reacted with chitosan. Quant. detn. of contour length distributions and persistence lengths showed that the triple-helical backbone of scleraldehyde was not disrupted due to this chem. modification. Fully carboxylated sclerox, sclerox1.0 revealed dispersed, flexible, coil-like structures, consistent with a electrostatic driven strand-sepn. of scleroglucan triplex obsd. concomitant with increasing degree of oxidn. The peristence lengths of sclerox0.4 and sclerox0.6 were detd. to 51±6 and 57± 7nm, resp., which is significantly less than 184± 23nm detd. for scleroglucan triple-helix structure. Sclerox1.0 was obsd. to be more flexible than sclerox0.4 and sclerox0.6. The pregel clusters when scleraldehyde was crosslinked with chitosan reveal networks with apparent pore sizes reflecting the degree of aldehyde substitution of scleraldehyde.
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|Titolo:||Ultramicroscopy of triple-helical polysaccharide scleroglucan: Strand-separation and network formation|
|Data di pubblicazione:||2001|
|Appartiene alla tipologia:||01a Articolo in rivista|