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|Type:||Artigo de periódico|
|Title:||Use of water spin-spin relaxation rate to probe the solvation of cyclodextrins in aqueous solutions|
|Abstract:||H-1 spin-spin relaxation rate constant, R-2, of water was measured by using the Carr-Purcell-Meiboom-Gill sequence in aqueous solutions of native cyclodextrins (alpha, beta and gamma-CD) and chemically modified CDs in order to probe the structuring of the water surrounding these cyclic carbohydrate molecules. R-2 values for water in solutions containing glucose and dextran were also measured for comparison. A two-site model for bonded and free water molecules was used to fit the results for the dependence of R-2 on the solute concentrations. The order of relaxation rates for water in aqueous solution at a fixed specific hydroxyl group concentration is glucose > dextran congruent to CDs. No significant difference was observed for R-2 of water in solutions containing native CDs, which indicates that the size and nature of the cavity has a small effect on the spin-spin relaxation times of water. The lower relaxation rate for water in CD solutions was attributed to the intramolecular hydrogen bonding formed between the secondary hydroxyl groups that line the rim of the CDs. For comparison, the relaxation rates for water in solutions of two chemically modified CDs were also studied.|
|Editor:||Amer Chemical Soc|
|Appears in Collections:||Unicamp - Artigos e Outros Documentos|
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