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Titolo:
X-ray, electrolytic conductance, and dielectric studies of bile salt micellar aggregates
Autore:
Bonincontro, A; DArchivio, AA; Galantini, L; Giglio, E; Punzo, F;
Indirizzi:
Univ Rome La Sapienza, INFM, Dipartimento Fis, I-00185 Rome, Italy Univ Rome La Sapienza Rome Italy I-00185 imento Fis, I-00185 Rome, Italy Univ Rome La Sapienza, Dipartimento Chim, I-00185 Rome, Italy Univ Rome LaSapienza Rome Italy I-00185 mento Chim, I-00185 Rome, Italy Univ Aquila, Dipartimento Chim Ingn Chim & Mat, I-67010 Coppito, Laquila, Italy Univ Aquila Coppito Laquila Italy I-67010 I-67010 Coppito, Laquila, Italy
Titolo Testata:
LANGMUIR
fascicolo: 26, volume: 16, anno: 2000,
pagine: 10436 - 10443
SICI:
0743-7463(200012)16:26<10436:XECADS>2.0.ZU;2-T
Fonte:
ISI
Lingua:
ENG
Soggetto:
BILIRUBIN-IX-ALPHA; SODIUM DEOXYCHOLATE; INTERACTION COMPLEXES; CRYSTAL-STRUCTURES; TAURODEOXYCHOLATE; TAUROCHOLATE; GLYCODEOXYCHOLATE; GLYCOCHOLATE; MODELS; RADIO;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
49
Recensione:
Indirizzi per estratti:
Indirizzo: Giglio, E Univ Rome La Sapienza, INFM, Dipartimento Fis, P A Moro 5, I-00185 Rome, Italy Univ Rome La Sapienza P A Moro 5 Rome Italy I-00185 Rome, Italy
Citazione:
A. Bonincontro et al., "X-ray, electrolytic conductance, and dielectric studies of bile salt micellar aggregates", LANGMUIR, 16(26), 2000, pp. 10436-10443

Abstract

Previously, structural models, observed in fibers and crystals, were proposed for sodium deoxycholate (NaDC), glycodeoxycholate (NaGDC), taurodeoxycholate (NaTDC), and taurocholate (NaTC) micellar aggregates, and were verified in aqueous solutions by means of several techniques. Here we report the X-ray analysis of sodium glycocholate (NaGC) fibers, which indicates that NaGC micellar aggregates could be formed by dimers and octamers as in the case of NaTC. Moreover, we present electrolytic conductance and dielectric measurements on NaGDC, NaTC, and NaGC aqueous micellar solutions to verify our micellar aggregate models. Specific conductance values of 0.1 mol dm(-3) NaDC, NaTDC, NaGDC, NaTC, and NaGC solutions containing NaCl at concentration ranging from 0 to 0.8 mol dm(-3) practically do not depend on the particular bile salt. Comparison with NaCl values shows that bile salt contribution to conductance decreases by increasing NaCl concentration, is nearly zero around the concentration range 0.5-0.6 mol dm(-3), and becomes negative at higher concentration. This behavior can be explained if Na+ ions stronglyinteract with bile salt anions and reinforce their interaction when micellar size increases. Even the inclusion of Na+ and Cl- ions, coming from NaCl, into micellar aggregates cannot be excluded, especially at high ionic strength. NaDC, NaTDC, NaGDC, NaTC, and NaGC present high values of the average electric dipole moment per monomer mu that can be justified by a remarkable hydration of their micellar aggregates. Reasonably, micellar aggregate composition and population change very slightly or do not change at all within the temperature range 15-45 degreesC, because mu is nearly constant in this interval. Results also suggest that Na+ ions are anchored to anions in dilute solution, thus forming ion pairs in the case of NaTC and NaGC, at least. Dihydroxy and trihydroxy bile salts are characterized by very similar cation-anion interaction strengths, even though their Structures are different. The trend of mu, which moderately decreases by increasing bile salt concentration, agrees with our structural models and can be due to coexistence of two structures, at least.

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Documento generato il 02/07/20 alle ore 22:05:07