title: The Influence of pH on the Scleroglucan and Scleroglucan/Borax Systems.
abstract: The effects that an increase of environmental pH has on the triple helix of scleroglucan (Sclg) and on the Sclg/borax hydrogel are reported. Rheological experiments show that the hydrogel is less sensitive to pH increase than Sclg alone, while at pH = 14 a dramatic viscosity decrease takes place for both systems. This effect is evidenced also by the reduced water uptake and anisotropic elongation detected, at pH = 14, by the swelling behaviour of tablets prepared with the Sclg/borax system. On the opposite, a different behaviour was observed with guar gum and locust bean gum tablets, tested as reference polysaccharides. The effect of pH on the structure of Sclg and Sclg/borax was investigated also by means of spectroscopic approaches based on the interaction between Congo red (CR) and the Sclg triple helix. Obtained results indicated that the CR absorbance maximum is shifted as a function of pH and by the presence of borax. Principal component analysis allowed very precise identification of the pH value at which the Sclg helix collapses. Molecular dynamics simulations of the Sclg/borax-CR complex indicated that, at physiological pH, only a few ordered configurations are populated, according to the induced circular dichroism (CD) spectrum evidence.
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome "Tor Vergata", Via della Ricerca Scientifica, 00133 Rome, Italy. claudia.mazzuca@uniroma2.it.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mazzuca
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome "Tor Vergata", Via della Ricerca Scientifica, 00133 Rome, Italy. gianfranco.bocchinfuso@uniroma2.it.
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Bocchinfuso
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome "Tor Vergata", Via della Ricerca Scientifica, 00133 Rome, Italy. antonio.palleschi@uniroma2.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Palleschi
authors.affiliation: Department of Chemical Sciences and Technologies, University of Rome "Tor Vergata", Via della Ricerca Scientifica, 00133 Rome, Italy. paolo.conflitti@uniroma2.it.
authors.forename: Paolo
authors.initials: P
authors.lastname: Conflitti
authors.affiliation: Department of Engineering and Architecture, University of Trieste, P.le Europa 1, 34127 Trieste, Italy. mario.grassi@di3.units.it.
authors.forename: Mario
authors.initials: M
authors.lastname: Grassi
authors.affiliation: Department of Drug Chemistry and Technologies, "Sapienza", University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy. chiara.dimeo@uniroma1.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Di Meo
authors.affiliation: Department of Drug Chemistry and Technologies, "Sapienza", University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy. franco.alhaique@uniroma1.it.
authors.forename: Franco
authors.initials: F
authors.lastname: Alhaique
authors.affiliation: Department of Drug Chemistry and Technologies, "Sapienza", University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy. tommasina.coviello@uniroma1.it.
authors.forename: Tommasina
authors.initials: T
authors.lastname: Coviello
mesh_terms: D001881:Borates / Q000737:chemistry*; D002942:Circular Dichroism; D004548:Elasticity; D005936:Glucans / Q000737:chemistry*; D020100:Hydrogels / Q000737:chemistry; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D008968:Molecular Conformation; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D012212:Rheology; D013607:Tablets / Q000737:chemistry; D014783:Viscosity
chemical_list: D001881:Borates; D005936:Glucans; D020100:Hydrogels; D013607:Tablets; C018851:borax; C045938:scleroglucan
keywords: Congo red; molecular dynamics simulations; principal component analysis; rheology; scleroglucan; swelling