Effect of sodium chloride on the binding of polyaromatic hydrocarbon guests with sodium cholate aggregates

Abstract

Sodium cholate aggregates are adaptable host systems. The effect of changing the ionic strength with the addition of NaCl on the properties for guest binding to sodium cholate aggregates was investigated by using pyrene, perylene and 1-ethylnaphthalene as guests. Fluorescence, anisotropy and laser flash photolysis studies provided information on the protection efficiency of the aggregate bound guest, and provided information on the dynamics and correlation times for the host-guest system. Different trends for the protection efficiency of the bound guests were observed when the NaCl concentration was raised depending on the charge of the aqueous solubilized quencher. The increase in ionic strength was also shown to lengthen the correlation time of the aggregate bound guest and led to faster dynamics for the host-guest complex. These results show that the properties of sodium cholate aggregates as a supramolecular host system are significantly altered with changes in the ionic strength of the medium.

Modulation of the aggregation properties of sodium deoxycholate in presence of hydrophilic imidazolium based ionic liquid: water dynamics study to probe the structural alteration of the aggregates

“…Therefore, an inflection point is observed at the CMC in the plot of the ratio I I /I III when pyrene experiences a change from the hydrophilic environment to the hydrophobic environment in the core of the micelle. 19 In the presence of 1 M NaCl, the I I /I III ratio of pyrene is decreased from 0.843 to 0.702 in the case of sodium cholate (NaCh) aggregates 19 and the decrease is mainly due to the decreased contact between aggregate bound pyrene and the water molecules close to the aggregates. However, with increasing concentration of bile salts the size of the aggregate is increased and therefore, the CMC value of the aggregate is broader than that of conventional surfactants.…”

“…19 Thus, an increase in the I I /I III ratio for the Py bound NaDC aggregate from 0.7 in the absence of [bmim]-BF 4 to 1.03 in the presence of 9.8 wt% [bmim]-BF 4 (0.43 M) suggests that a significant increase occurs in the polarity of the NaDC binding sites, and the behavior of the IL correlates well with organic cosolvents, where the water accessibility to the binding sites of the aggregates is increased with the addition of cosolvents and upon performing control experiments it can also be concluded that in the presence of a high concentration of IL, pyrene does not relocate itself to the [bmim]-BF 4 aggregates or to the water medium. 19 Thus, an increase in the I I /I III ratio for the Py bound NaDC aggregate from 0.7 in the absence of [bmim]-BF 4 to 1.03 in the presence of 9.8 wt% [bmim]-BF 4 (0.43 M) suggests that a significant increase occurs in the polarity of the NaDC binding sites, and the behavior of the IL correlates well with organic cosolvents, where the water accessibility to the binding sites of the aggregates is increased with the addition of cosolvents and upon performing control experiments it can also be concluded that in the presence of a high concentration of IL, pyrene does not relocate itself to the [bmim]-BF 4 aggregates or to the water medium.…”

“…Bhattacharyya et al determined the time resolved anisotropy decays of C-153 by varying the excitation wavelengths and they showed that the anisotropy decays do not show any appreciable dependence on excitation wavelength. 19 However, a significant increase in the viscosity is observed after the addition of a low wt% of IL to the NaDC aggregates. At l exc = 408 nm and l exc = 440 nm, the average rotational relaxation time of C-153 in 20 mM NaDC aggregates is (1.42 AE 0.07) ns and (1.39 AE 0.08) ns, respectively ( Table 2).…”

“…Both hydrophobic and hydrogen bonding interactions play an important role in the formation of primary aggregates. However, the aggregation behavior of bile salts and consequently, the efficiency and binding dynamics of the guest molecules are severely altered in the presence of electrolytes 19,20 or other organic solvents like acetonitrile (ACN), dimethyl formamide (DMF), methanol (MeOH), ethylene glycol, etc. Due to this unique aggregation behavior, bile salt has the ability to solubilize various biologically active organic guest molecules, which include many sparingly water soluble drug molecules, [6][7][8][9][10][11][12][13][14] and finally it helps to control various chemical reactions such as photoinduced, enzymatic and complexation reactions.…”

“…The shape, size and hydrophobicity of the aggregates determine the binding efficiency, location and protection efficiency of the guest molecules. However, the aggregation behavior of bile salts and consequently, the efficiency and binding dynamics of the guest molecules are severely altered in the presence of electrolytes 19,20 or other organic solvents like acetonitrile (ACN), dimethyl formamide (DMF), methanol (MeOH), ethylene glycol, etc. [21][22][23] The binding dynamics of the aggregates is strongly influenced by the ionic strength of the medium and it is well known that the Critical Micellar Concentration (CMC) of the aggregates is decreased along with the increase in the size of the aggregates, as we increase the ionic strength of the medium and the size increase is more prominent in dihydroxy bile salts compared to other trihydroxy salts due to their substantial hydrophobicity.…”