title: 23Na and 35/37Cl as NMR probes of growth and shape of sodium taurodeoxycholate micellar aggregates in the presence of NaCl.
abstract: The growth of the aggregates of the dihydroxylated bile salt sodium taurodeoxycholate (NaTDC) upon NaCl addition and the involvement of the counterion were investigated by NMR spectroscopy of monoatomic ionic species. (23)Na T(1) values from 0.015, 0.100, and 0.200 mol kg(-1) NaTDC solutions in D(2)O, at variable NaCl content, proved to be sensitive to the transition from primary to secondary aggregates, which occurs in the former sample, and to intermicellar interaction. Some (79)Br NMR measurements were performed on a 0.100 mol kg(-1) NaTDC sample added by NaBr in place of NaCl for comparison purposes. The (23)Na, (35)Cl, and (37)Cl double quantum filtered (DQF) patterns, from the 0.100 mol kg(-1) NaTDC sample, and (23)Na ones also from the 0.200 mol kg(-1) NaTDC one, in the presence of 0.750 mol kg(-1) NaCl, are a clear manifestation of motional anisotropy. Moreover, the DQF spectra of (23)Na and (37)Cl, which possess close quadrupole moments, display a striking similarity. The DQF lineshapes were simulated exploiting the Scilab environment to obtain an estimate of the residual quadrupole splitting magnitude. These results support the description of NaTDC micelles as cylindrical aggregates, strongly interacting at high ionic strengths, and capable of association with added electrolytes.
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy. Electronic address: fasaro@units.it.
authors.forename: Fioretta
authors.initials: F
authors.lastname: Asaro
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy. Electronic address: luigi.feruglio@yahoo.it.
authors.forename: Luigi
authors.initials: L
authors.lastname: Feruglio
authors.affiliation: Department of Chemistry, University of Rome "La Sapienza", P. le A. Moro 5, 00185 Rome, Italy. Electronic address: l.galantini@caspur.it.
authors.forename: Luciano
authors.initials: L
authors.lastname: Galantini
authors.affiliation: Department of Chemical and Pharmaceutical Sciences, University of Trieste, via L. Giorgieri 1, 34127 Trieste, Italy. Electronic address: giallotweety@libero.it.
authors.forename: Alessia
authors.initials: A
authors.lastname: Nardelli
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D007554:Isotopes; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D012964:Sodium / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D013657:Taurodeoxycholic Acid / Q000737:chemistry*
chemical_list: D007554:Isotopes; D008823:Micelles; D012965:Sodium Chloride; D002713:Chlorine; D013657:Taurodeoxycholic Acid; D012964:Sodium