Self-association of sodium isoursodeoxycholate and sodium isohenodeoxycholate in water

Tepavčević, Vesna; Pilipović, Ana; Agatić, Zita Farkaš; Popović, K; Poša, Mihalj

doi:10.1016/j.chemphyslip.2019.05.003

Cited by 5 publications

(4 citation statements)

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“…[ 4,39 ] If there are polar groups on the surface of a molecular object, which can form hydrogen bonds with water molecules from the hydration layer, then water molecules can compensate the reduction of entropy with the released H‐bond energy—stabilized water molecules (SWM) in the hydration layer. [ 3,4,40 ] The higher the amount of NSWM in the hydration shell of a molecular object, the greater its tendency to associate with a hydrophobic surfaces, such as a hydrophobic stationary phase or a hydrophobic surface of another molecular object (self‐association); that is, hydrophobicity is proportional to the number of NSWM. [ 41,42 ]…”

Section: Resultsmentioning

confidence: 99%

Hydrophobicity and self‐association (micellization) of bile salts with a lactone or lactam group in a steroid skeleton

Poša

Tepavčević

Grbović

et al. 2020

J of Physical Organic Chem

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Bile acid salts are amphiphiles that have planar polarity: the convex surface (the β side) of their steroid skeleton is hydrophobic, whereas the concave surface (the α side) is hydrophilic. Lactone and lactam derivatives of bile acid salts have reduced hydrophobicity on the convex surface (β side) of the steroid skeleton, but they are still able to build micelles. In the vicinity of their critical micellar concentration (CMC), they probably form Small's primary micelles. In this work, it is shown that retention capacities (reverse-phase highperformance liquid chromatography) are linearly dependent on temperature, for each tested bile acid. The parameters of this linear dependence (intercept and slope) can be used to describe the hydrophobicity of the analyzed bile acid salts. The first and the second principal components, derived from the covariance matrix of temperature dependence of retention capacity, can also be used as hydrophobicity parameters of the analyzed bile acid salts. There is a strong correlation between the CMC values and the values of the hydrophobicity parameters of the convex surface (the β side) of the steroid skeleton: the CMC values decrease as the hydrophobicity of the β side of the steroid skeleton decreases.

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Section: Resultsmentioning

confidence: 99%

Hydrophobicity and self‐association (micellization) of bile salts with a lactone or lactam group in a steroid skeleton

Poša

Tepavčević

Grbović

et al. 2020

J of Physical Organic Chem

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“…When the aqueous solution/air boundary layer becomes saturated with surfactant particles, the entropy of the system can further increase if dehydration of the hydrophobic molecular surfaces continues, with the hydrophobic surfaces assembling into micelles (bile salts into primary micelles) to prevent re-hydrophobic hydration [4,48,51,54,55]. In the case of bile salts, the steroid skeleton is relatively rigid (it has little conformational mobility); therefore, in the micelle, there is a slight mutual correlation of internal molecular movements (rotation)-to prevent hydrophobic hydration of the micelle-so that part of the convex molecular surfaces of the steroid skeleton in the micellar state remains hydrated [48,[54][55][56] (Figure A3). Water molecules in the solvation layer above the hydrophilic molecular surface also have a smaller degree of freedom compared to water molecules from inside the solution; however, this is compensated by the enthalpy of the formation of hydrogen bonds with OH groups from the concave side of the steroid skeleton-stabilized water molecule (SWM) (Figure A3).…”

Section: Appendix Bmentioning

confidence: 99%

“…Namely, with increasing temperature, the mobility of NSWM in the solvation layer above the hydrophobic molecular surface of surfactants increases; therefore, their molar entropy equals the molar entropy of water molecules from bulk solution-the temperature at which the change in entropy of micellization is zero. At the same time, as the temperature increases, the intensity of van der Waals intermolecular interactions between the hydrophobic surfaces in micelles increases, which results in the release of enthalpy (heat at constant pressure)-a hydrophobic interaction [4,[47][48][49][50][51][52][53][54][55][56].…”

Section: Appendix Bmentioning

confidence: 99%

“…However, classic surfactants and bile acid salts share that at lower temperatures, micelles (primary micelles) are formed through entropic driving forces-the hydrophobic effect. With the increase in temperature, the micellization process of classic surfactants and bile acid salts has an enthalpic driving force [4,13,[47][48][49][50][51][52][53][54][55][56][57][58] (Appendix B).…”

Section: Introductionmentioning

confidence: 99%

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Self-Association of the Anion of 7-Oxodeoxycholic Acid (Bile Salt): How Secondary Micelles Are Formed

Poša

2023

IJMS

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Bile acid anions are steroidal biosurfactants that form primary micelles due to the hydrophobic effect. At higher concentrations of some bile acid anions, secondary micelles are formed; hydrogen bonds connect primary micelles. Monoketo derivatives of cholic acid, which have reduced membrane toxicity, are important for biopharmaceutical examinations. The main goal is to explain why the processes of formation of primary and secondary micelles are separated from each other, i.e., why secondary micelles do not form parallel to primary micelles. The association of the anion of 7-oxodeoxycholic acid (a monoketo derivative of cholic acid) is observed through the dependence of the spin–lattice relaxation time on total surfactant concentration T1 = f(CT). On the function T1 = f(CT), two sharp jumps of the spin–lattice relaxation time are obtained, i.e., two critical micellar concentrations (CMC). The aggregation number of the micelle at 50 mM total concentration of 7-oxodeoxycholic acid anions in the aqueous solution is 4.2 ± 0.3, while at the total concentration of 100 mM the aggregation number is 9.0 ± 0.9. The aggregation number of the micelle changes abruptly in the concentration interval of 80–90 mM (the aggregation number determined using fluorescence measurements). By applying Le Chatelier’s principle, the new mechanism of formation of secondary micelles is given, and the decoupling of the process of formation of primary and secondary micelles at lower concentrations of monomers (around the first critical micellar concentration) and the coupling of the same processes at higher equilibrium concentrations of monomers (around the second critical micellar concentration) is explained. Stereochemically and thermodynamically, a direct mutual association of primary micelles is less likely, but monomeric units are more likely to be attached to primary micelles, i.e., 7-oxodeoxycholic acid anions.

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Effects of additives (methanol and NaCl) from aqueous surfactant solutions on the micellisation of sodium deoxycholate and sodium cholate binary mixture in the temperature interval T = (278.15–318.15) K: The molar excess Gibbs energy and the molar Gibbs energy of the micelle formation

Poša

Pilipović

2020

The Journal of Chemical Thermodynamics

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Self-association of sodium isoursodeoxycholate and sodium isohenodeoxycholate in water

Cited by 5 publications

References 34 publications

Hydrophobicity and self‐association (micellization) of bile salts with a lactone or lactam group in a steroid skeleton

Hydrophobicity and self‐association (micellization) of bile salts with a lactone or lactam group in a steroid skeleton

Self-Association of the Anion of 7-Oxodeoxycholic Acid (Bile Salt): How Secondary Micelles Are Formed

Effects of additives (methanol and NaCl) from aqueous surfactant solutions on the micellisation of sodium deoxycholate and sodium cholate binary mixture in the temperature interval T = (278.15–318.15) K: The molar excess Gibbs energy and the molar Gibbs energy of the micelle formation

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