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Aggregation behavior of bile salts in aqueous solution
A Coello1, F Meijide, E R Núñez
1Departamento de Química Física, Universidad de Santiago, Lugo, Spain.
Journal of Pharmaceutical Sciences
|January 1, 1996
Summary
Aqueous solutions of bile salts (NaTC, NaDC, NaTDC) exhibit critical micelle concentrations, forming aggregates with distinct aggregation numbers and bound counterion fractions. These findings aid in understanding bile salt aggregate structures.
Area of Science:
- Physical chemistry
- Biochemistry
- Colloid science
Background:
- Bile salts are crucial biological surfactants.
- Understanding their aggregation behavior is key to their function.
- Previous studies established critical micelle concentrations (CMCs).
Purpose of the Study:
- To analyze aggregation behavior of trihydroxy (NaTC) and dihydroxy (NaDC, NaTDC) bile salts in aqueous solutions.
- To determine aggregation numbers and bound counterion fractions.
- To discuss structural models of bile salt aggregates.
Main Methods:
- Measurement of freezing point depression (delta T/k) and sodium ion activity (pNa).
- Analysis of delta T/k versus molality plots to identify critical micelle concentrations (CMCs).
- Calculation of average aggregation numbers and fractions of bound counterions.
Main Results:
- Identified break points (CMCs) at 0.018 m (NaTC), 0.013 m (NaDC), and 0.007 m (NaTDC).
- Determined average aggregation numbers: 2.59 (NaTC), 5.82 (NaDC), 5.42 (NaTDC).
- Deduced bound counterion fractions close to 0.3, indicating one bound ion per three monomers.
Conclusions:
- Bile salt solutions exhibit distinct aggregation behavior above their CMCs.
- The aggregation numbers and counterion binding are characteristic for each bile salt.
- Findings provide insights into bile salt aggregate structures and their properties.