Water and carbohydrates: macroscopic and molecular aspects of their interactions

Author(s)

Marcus Vinicíus Cangussu Cardoso

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2012-04-27

Examining board members

Edvaldo Sabadini; Luiz Alberto Colnago; Eduardo Ribeiro de Azevedo; Alviclér Magalhães; Pedro Luiz Onófrio Volpe

• Advisor: Munir Salomão Skaf; Edvaldo Sabadini

Abstract

Aqueous solutions of mono, di, oligo, and polysaccharides were studied on the macroscopic and molecular standpoints through thermodynamic and spectroscopic approaches. The effect of hydrogen-bonding strength on the solubility of a series of (linear and cyclic) saccharides showed to be strongly dependent of the solubility of the carbohydrate. As lower is the solubility of the carbohydrate, greater will be the deuterium isotopic effect of the solvent (H2O for D2O) on the carbohydrate solubilities. These results suggest that low soluble carbohydrates (and larger ones) perturb more strongly the water structure. Owing to the cooperativity of the coil-helix transition, the deuterium isotope effect on the gelling of k-carrageenan is intensified leading to stronger gels and double-helices more stable in D2O. Looking deeper onto a molecular perspective and based on spin-spin nuclear magnetic relaxation, the proton exchange rates, kb, between water and OH-carbohydrate, are dependent of the nature of the saccharide. The kb values are higher for linear than for pyranoside form, and the slowest value is found for fructofuranoside form. The transferring of magnetization between proton pools of water and CH-carbohydrates are modulated by molecular motions and intermediated by proton exchanging process between water and OH-carbohydrate protons. H NMR relaxation experiments of exchangeable protons provide to be rich in probing the micelar aggregation of n-alkyl-glucosides. It was possible to demonstrate experimentally that the aggregation of the surfactant molecules provoke a drastic reduction on the interactions between water and OH-saccharide head groups (AU)

• FAPESP's process: 08/00908-4 - WATER AND CARBOHYDRATES: MACROSCOPIC AND MOLECULAR ASPECTS OF THEIR INTERACTIONS
• Grantee: Marcus Vinícius Cangussu Cardoso
• Support Opportunities: Scholarships in Brazil - Doctorate