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Titolo:
On the role of hydronium ions in the protonated micellar aggregates of bile salts
Autore:
De Sanctis, SC; DArchivio, AA; Galantini, L; Gavuzzo, E; Giglio, E;
Indirizzi:
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, Italy Univ Aquila Coppito Italy I-67010 ngn Chim & Mat, I-67010 Coppito, Italy CNR, Ist Strutturist Chim Giordano Giacomello, I-00016 Monterotondo Stn, Roma, Italy CNR Monterotondo Stn Roma Italy I-00016 016 Monterotondo Stn, Roma, Italy
Titolo Testata:
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
fascicolo: 2, , anno: 2000,
pagine: 403 - 407
SICI:
0300-9580(2000):2<403:OTROHI>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
BILIRUBIN-IX-ALPHA; SODIUM DEOXYCHOLATE; X-RAY; INTERACTION COMPLEXES; CRYSTAL-STRUCTURES; AQUEOUS-SOLUTIONS; TAURODEOXYCHOLATE; GLYCODEOXYCHOLATE; GLYCOCHOLATE; TAUROCHOLATE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
40
Recensione:
Indirizzi per estratti:
Indirizzo: Giglio, E Univ Rome La Sapienza, Dipartimento Chim, P A Moro 5, I-00185 Rome, Italy Univ Rome La Sapienza P A Moro 5 Rome Italy I-00185 Rome, Italy
Citazione:
S.C. De Sanctis et al., "On the role of hydronium ions in the protonated micellar aggregates of bile salts", J CHEM S P2, (2), 2000, pp. 403-407

Abstract

In previous work, structural units observed in bile salt crystals and fibres have been successfully used to represent bile salt micellar aggregates in aqueous solutions and electromotive force measurements have shown that protonated micellar species are present below some critical values of pH. This paper deals with the crystal structures of 3 alpha,12 alpha-dihydroxy-5 beta-cholanoylglycine (HGDC), 3 alpha,12 alpha-dihydroxy-5 beta-cholanoyltaurine (HTDC) and 3 alpha,7 beta-dihydroxy-5 beta-cholanoyltaurine (HTUDC), which were solved to obtain models of protonated micellar aggregates. The models are compared with those found in crystals and fibres of sodium and rubidium salts of HGDC and HTDC (NaGDC, NaTDC, RbGDC, RbTDC) in order to verify whether the acid structures match with the salt structures. The HGDC packing resembles that of a NaTDC crystal and is stabilized mainly by hydrogen bonds as well as by dipole-dipole interactions between acetone molecules and carboxylic groups. Three different 3(1) helices are identified. One of these can be easily transformed into the 7/1 helix which satisfactorily describes the NaGDC, NaTDC, RbGDC and RbTDC micellar aggregates. The HTDC and HTUDC crystal structures are practically the same. Strong hydrogen bonds between H3O+ (hydronium ion) and three oxygen atoms of the anions show O ... O distances within the range 2.4-2.6 Angstrom, owing to additional ion-ion and ion-dipole interactions. Very probably, H3O+ replaces Na+ in the micellaraggregates without remarkably changing their structure because the H3O+... O and Na+... O distances are very close. Inspection of previous electromotive force data indicates that the glycodeoxycholate and taurodeoxycholate micellar aggregates' proton affinities increase as their sizes increase and that those of the bigger aggregates seem to converge, even though the proton affinity of COO- is greater than that of SO3-. These findings strongly suggest that micellization induces H3O+ binding. HTDC and HTUDC form micellaraggregates which increase their apparent hydrodynamic radius by adding HCl.

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Documento generato il 22/09/20 alle ore 04:25:02