Calorimetric and optical study of micellar aggregates of sodium taurodeoxycholate

D'Alagni, M.; Giglio, E.; Petriconi, Silvio

doi:10.1007/bf01412505

Cited by 16 publications

(15 citation statements)

References 16 publications

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“…A competing model proposes that the primary interaction is due to the formation of hydrogen bonds between the monomers, leading to interactions between the hydrophilic faces of the bile salt molecules. 19,22,[42][43][44][45][46][47][48] Our earlier work with bile salt aggregates 35,36,39-41 is consistent with the primary/secondary aggregation model, since it was found that hydrophobic guest molecules are located in a hydrophobic and protected environment inside the bile salt aggregates. Singlet excited states have short lifetimes and they cannot relocate before the excited state decays to the ground state.…”

Section: Introductionsupporting

confidence: 78%

Probing the binding dynamics to sodium cholate aggregates using naphthalene derivatives as guests

Rinco

Nolet

Ovans

et al. 2003

Photochem Photobiol Sci

151

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The binding dynamics with bile salt aggregates for a series of naphthalene derivatives of different polarities was studied using fluorescence and laser flash photolysis. Fluorescence was employed to determine the nature of the binding site for each guest and the accessibility of the bound guest to quenchers. Laser flash photolysis was employed to study the mobility of the triplet states of the naphthalenes between the sodium cholate aggregates and the aqueous phase. Primary aggregates, which provide an environment protected from quenchers in the aqueous phase, bind 1- and 2-ethylnaphthalene as guests. The complexation dynamics with this type of aggregate is slow. 1- and 2-Naphthyl-1-ethanol, and 1- and 2-acetonaphthone bind to the secondary aggregates, which provide moderate protection from quenching and faster binding dynamics. The addition of salts lowered the cholate concentration at which primary aggregates were formed, but did not influence the formation of secondary aggregates.

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Section: Introductionsupporting

confidence: 78%

Probing the binding dynamics to sodium cholate aggregates using naphthalene derivatives as guests

Rinco

Nolet

Ovans

et al. 2003

Photochem Photobiol Sci

151

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“…Passing from the premicellar to the micellar state, NaCDC, NaDC, and sodium cholate 29 decrease their rotational strength because of aggregation, in contrast with NaTDC. 30 The most interesting feature of the CD spectra is the position of the minima centered at about 202 and 209 nm for NaCDC and NaDC, respectively. The carboxylate and, to a less extent, the carboxylic groups are the chromophores mainly responsible for the absorption and, therefore, are involved in different interactions in the two salts.…”

Section: Resultsmentioning

confidence: 99%

“…The NaCDC molar ellipticity is greater than that of NaDC. Passing from the premicellar to the micellar state, NaCDC, NaDC, and sodium cholate decrease their rotational strength because of aggregation, in contrast with NaTDC . The most interesting feature of the CD spectra is the position of the minima centered at about 202 and 209 nm for NaCDC and NaDC, respectively.…”

Section: Resultsmentioning

confidence: 99%

Structural Study of the Micellar Aggregates of Sodium Chenodeoxycholate and Sodium Deoxycholate

D'Alagni¹,

D’Archivio²,

Galantini³

et al. 1997

Langmuir

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Quasi-elastic light-scattering data of sodium chenodeoxycholate (NaCDC), sodium deoxycholate (NaDC), and sodium taurodeoxycholate (NaTDC) show that the micellar size increases upon increasing ionic strength (NaCDC, NaDC, and NaTDC) and upon decreasing temperature and pH (NaCDC and NaDC). Their mean hydrodynamic radii (Rh) are in the following order: NaDC > NaTDC > NaCDC. The difference between the Rh values of NaDC and NaCDC is negligible without NaCl and increases upon increasing the NaCl concentration. The average intensities scattered by 0.01-0.10 M aqueous solutions are in the sequence NaTDC > NaDC > NaCDC. Thus, the growth of NaCDC is less than those of NaDC and NaTDC. The plots of the average intensity vs the square root of the mole fraction show that the experimental data are fitted by one straight line for NaCDC and two straight lines for NaDC and NaTDC, suggesting that the NaCDC or NaDC and NaTDC micellar aggregates can be represented by one or two structures, respectively. Since the R-h and the average intensity values of NaCDC and NaDC with added NaCl decrease by increasing the temperature within the range 15-85 degrees C, their micellar aggregates are stabilized mainly by polar interactions as well as the helical micellar aggregates previously proposed for NaDC and NaTDC. The decrease of pH causes a slight increase of the R-h values of NaDC and NaCDC up to a certain pH value, where a sudden increase is observed. Circular dichroism spectra of NaDC and NaCDC aqueous solutions above and below the critical micellar concentration indicate that the two salts give rise to different types of aggregation. Those of the interaction complexes between bilirubin-IXa and NaCDC or NaDC or NaTDC suggest that the micellar structures are chiral and helical. The enantioselective abilities of NaDC and NaTDC are somewhat similar, but they are different from that of NaCDC. The X-ray fiber patterns of NaCDC, NaDC, and NaTDC can be interpreted by means of different helices and support the quasi-elastic light-scattering and circular dichroism results

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“…The validity of some models was verified by studying aqueous solutions of the micellar aggregates and of their interaction complexes with probe molecules as, for example, bilirubin-IXα (BR) and a spin-labeled cholestane. Small-angle X-ray scattering, nuclear magnetic resonance, ,− electron spin resonance, EXAFS, − and circular dichroism ,,,,, (CD) measurements together with energy calculations 3,10,12,16 were performed. The type of helical structure found in the NaDC and RbDC crystals satisfactorily explains the experimental data of the micellar aggregates. ,,,,,− This structure is similar to that of the NaGDC crystal (Figure a).…”

Section: Introductionmentioning

confidence: 99%

Structural Study of the Micellar Aggregates of Sodium and Rubidium Glyco- and Taurodeoxycholate

et al. 1996

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Some salts of bile acids increase the size of their micellar aggregates in aqueous solutions by varying parameters such as pH or ionic strength and give rise to transitions: aqueous micellar solution --> gel --> fiber --> crystal. Helical fibers of sodium and rubidium salts of glycodeoxycholic and taurodeoxycholic acids (NaGDC, RbGDC, NaTDC, and RbTDC, respectively) were drawn from aqueous solutions and investigated by means of X-ray diffraction analysis to clarify the structure of their micellar aggregates and to verify whether the micellar structures of the sodium and rubidium salts were similar. In this case, the rubidium salts can be studied in place of the sodium ones by extended X-ray absorption fine structure spectroscopy. The X-ray patterns of the NaGDC, RbGDC, NaTDC, and RbTDC fibers showed a close resemblance and were interpreted by means of very similar unit cell parameters and helical structures, formed by trimers arranged in 7/1 helices. Calculations of interatomic distances provided a model of the 7/1 helix which satisfactorily packs into the unit cells of the fibers. Quasi-elastic light-scattering measurements carried out on aqueous micellar solutions up to a concentration of NaCl or RbCl of about 0.3 M supported the similarity among the structures of the NaGDC, RbGDC, NaTDC, and RbTDC micellar aggregates. Oligomers of small size were observed without NaCl or RbCl. The extent of micellar growth increased upon increasing NaCl or RbCl concentration. The micellar size, which seemed to be dependent on the peculiar cation-anion Coulombic interaction starting from a NaCl or RbCl concentration of about 0.2 M, was in the following order: NaGDC > NaTDC approximate to RbTDC > RbGDC. Electromotive force measurements accomplished on NaTDC solutions at constant ionic medium provided the distribution of micellar sizes. Most of the aggregates have aggregation numbers that are a multiple of 3. The fraction of bound Na+ ions is high in accordance with an ordered structure like that of the 7/1 helix. Further support for the 7/1 helix came from the calculation of mean hydrodynamic radii using the helical model. The agreement with quasi-elastic light-scattering measurements at low bile salt concentration and within a wide range of ionic strength was satisfactory. The helical structure of the anions seems to be similar in the micellar aggregates of NaGDC, RbGDC, NaTDC, RbTDC, and tetramethylammonium taurodeoxycholate

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Calorimetric and optical study of micellar aggregates of sodium taurodeoxycholate

Cited by 16 publications

References 16 publications

Probing the binding dynamics to sodium cholate aggregates using naphthalene derivatives as guests

Probing the binding dynamics to sodium cholate aggregates using naphthalene derivatives as guests

Structural Study of the Micellar Aggregates of Sodium Chenodeoxycholate and Sodium Deoxycholate

Structural Study of the Micellar Aggregates of Sodium and Rubidium Glyco- and Taurodeoxycholate

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