The effects that an increase of environmental pH has on the triple helix of scleroglucan (Sclg)udand on the Sclg/borax hydrogel are reported. Rheological experiments show that the hydrogel is lessudsensitive to pH increase than Sclg alone, while at pH = 14 a dramatic viscosity decrease takes place forudboth systems. This effect is evidenced also by the reduced water uptake and anisotropic elongationuddetected, at pH = 14, by the swelling behaviour of tablets prepared with the Sclg/borax system.udOn the opposite, a different behaviour was observed with guar gum and locust bean gum tablets,udtested as reference polysaccharides. The effect of pH on the structure of Sclg and Sclg/borax wasudinvestigated also by means of spectroscopic approaches based on the interaction between Congo redud(CR) and the Sclg triple helix. Obtained results indicated that the CR absorbance maximum is shiftedudas a function of pH and by the presence of borax. Principal component analysis allowed very preciseudidentification of the pH value at which the Sclg helix collapses. Molecular dynamics simulations ofudthe Sclg/borax–CR complex indicated that, at physiological pH, only a few ordered configurationsudare populated, according to the induced circular dichroism (CD) spectrum evidence.
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