Development of an equilibrium headspace gas chromatographic method for the measurement of noncovalent association and partitioning of n-alkylbenzenes at infinite dilution in fulvic acid pseudophase

Eljack, Mahmoud; Wilson, Rachael E.; Hussam, Abul; Khan, Shahamat U.

doi:10.1016/j.chroma.2015.01.021

Cited by 3 publications

(6 citation statements)

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“…These data were used for the determination of the cac, K 11 , K n 1 , K x , and γ m . The statement “method quantitation limit, MQL” indicates that the peak area and corresponding vapor pressure of the perfume was less than 18 μTorr …”

Section: Resultsmentioning

confidence: 99%

“… a Uncertainties are provided in the form of the 95% confidence interval. b The method of initial slopes was used to calculate the cac …”

Section: Resultsmentioning

confidence: 99%

“…Bovine MBP (purified ≥ 90%, MW 18.4 kDa), in the form of a lyophilized powder, was used to make a protein solution (Sigma-Aldrich, catalog # 13104). A self-made computer-controlled eHSGC sampled the vapor phase above an infinitely dilute perfume solution containing varying concentrations of MBP. , A brief description of the instrument and procedure is presented in the Supporting Information (S1).…”

Section: Methodsmentioning

confidence: 99%

“…Here, we invoke a two-step general reaction model previously developed by Hussam et al − We assume that the following noncovalent association events occur in an aqueous perfume solution at infinite dilution to which dilute MBP is added Here, PC is a perfume component, MBP–PC is the monomeric complex with association constant K 11 , MBP n is the aggregate where n is the aggregation number, K n 1 is the association constant for the complex MBP n -PC, and cac is the critical aggregation concentration of MBP. The cac defines the concentration above which any additional MBP added to the solution will form an aggregate pseudophase.…”

Section: Theorymentioning

confidence: 99%

“…For each MBP addition, vapor in the headspace was sampled after an equilibration period. Similar investigations involve the characterization of binding events between larger molecules, including lipids and surfactants, with MBP, using techniques like spectrophotometric methods. − With eHSGC, a greater variety of thermodynamic parameters can be obtained for several solutes at infinite dilution simultaneously without the solute concentration. − Additionally, the data are not limited to monomeric MBP, as they span the pre- and post-aggregation pseudophase for the protein. This may provide an understanding of the unique ligand-binding features of MBP, as well as how fragrance molecules behave in biological systems.…”

Section: Introductionmentioning

confidence: 99%

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Noncovalent Association and Partitioning of Some Perfume Components at Infinite Dilution with Myelin Basic Protein Pseudophase in Normal Saline

et al. 2021

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Myelin basic protein (MBP), one of the major protein constituents of the myelin sheath, possesses unique ligand-binding features. We present a novel equilibrium headspace gas chromatographic technique to examine the thermodynamics of noncovalent interactions between common perfume components: Lilial, Hedione, Hexylcinnamic aldehyde, and Versalide with MBP monomers and its hexameric MBP-pseudophase. A general theoretical model is used to calculate the critical aggregation concentration (cac) of MBP, perfume component binding constants with monomeric MBP, K 11, and MBP as pseudophase, K n1, and free energies for perfume component binding with monomeric MBP, ΔG b,11, and MBP as pseudophase, ΔG b,n1. In addition, the pseudophase–water partition coefficients, K x, the free energies of transfer of perfume from bulk water to the MBP-pseudophase, ΔG t, and the intra-aggregate activity coefficients, γm ∞, at infinite dilution were also determined. The cac value measured by the method of fractional distribution is a unique and precise approach in understanding the aggregation phenomenon. Within the experimental error, the 1:1 binding free energies did not differ by more than 1 kJ/mol among the perfume components but favored the MBP pseudophase binding by 6 kJ/mol. Therefore, that protein aggregation can enhance the binding of small molecules is probably a general conclusion. While the magnitudes of K 11, K n1, ΔG b, K x, and ΔG t show weak trends, the γm ∞ values show a strong and distinct trend in interaction, spanning 4 orders of magnitude among the perfume components.

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Section: Resultsmentioning

confidence: 99%

“… a Uncertainties are provided in the form of the 95% confidence interval. b The method of initial slopes was used to calculate the cac …”

Section: Resultsmentioning

confidence: 99%