Biomaterial Database

The influence of bile salt structure on self-association in aqueous solutions. 1983

A Roda, and A F Hofmann, and K J Mysels

The relationship between chemical structure and the concentration at which self-association occurs in water or in 0.15 M Na+ ion was examined for more than 50 bile salts and bile salt analogues varying in substituents on the steroid nucleus or in the structure of the side chain. Nuclear substituents varied in type (alpha- or beta-hydroxy, or oxo group) and number (1, 2, or 3); side chain structure varied in the nature of the ionic group (unconjugated, glycine- or taurine-conjugated, or zwitterion) or length of the side chain (5-, 4-, or 3-carbon atoms). The midpoint of the concentration range over which aggregation occurred was called the critical micellar concentration (CMC), even though bile salt aggregation is known to be more gradual than that of most typical ionic detergents. CMC values were obtained by surface tension measurements using an improved maximum bubble-pressure method, as well as by dye solubilization. Results obtained by the two methods agreed well. The CMC values varied from about 1 to greater than 250 mM. For a given bile salt, the addition of a hydroxy or oxo group increased the CMC; and for a given number of substituents, the changing of a hydroxy group to an oxo group increased the CMC values as well. The orientation of hydroxy substituents also influenced the CMC values: the changing of a hydroxy substituent from an alpha- to a beta-configuration increased the CMC values, as bile salts possessing alpha- and beta-hydroxy substituents had higher CMC values than bile salts with only alpha-hydroxy substituents. Inspection of space-filling models suggested the hypothesis that the greater contiguous hydrophobic area of the molecule, the lower the CMC value. The CMC value also increased exponentially as the side chain was shortened from C5 to C4 to C3. Conjugation of the side chain carboxylic group with glycine or taurine, although increasing the length of the side chain, caused little change in the CMC values. The addition of Na+ ion to a total concentration of 0.15 M lowered the CMC in a predictable manner for all anionic bile salts. The results indicate that the concentration at which bile salt aggregation occurs varies widely and is determined not only by the number, type, and orientation of nuclear substituents, but also by side chain structure.

UI	MeSH Term	Description	Entries
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D008823	Micelles	Particles consisting of aggregates of molecules held loosely together by secondary bonds. The surface of micelles are usually comprised of amphiphatic compounds that are oriented in a way that minimizes the energy of interaction between the micelle and its environment. Liquids that contain large numbers of suspended micelles are referred to as EMULSIONS.	Micelle
D008968	Molecular Conformation	The characteristic three-dimensional shape of a molecule.	Molecular Configuration,3D Molecular Structure,Configuration, Molecular,Molecular Structure, Three Dimensional,Three Dimensional Molecular Structure,3D Molecular Structures,Configurations, Molecular,Conformation, Molecular,Conformations, Molecular,Molecular Configurations,Molecular Conformations,Molecular Structure, 3D,Molecular Structures, 3D,Structure, 3D Molecular,Structures, 3D Molecular
D002621	Chemistry	A basic science concerned with the composition, structure, and properties of matter; and the reactions that occur between substances and the associated energy exchange.
D004396	Coloring Agents	Chemicals and substances that impart color including soluble dyes and insoluble pigments. They are used in INKS; PAINTS; and as INDICATORS AND REAGENTS.	Coloring Agent,Dye,Dyes,Organic Pigment,Stain,Stains,Tissue Stain,Tissue Stains,Organic Pigments,Pigments, Inorganic,Agent, Coloring,Inorganic Pigments,Pigment, Organic,Pigments, Organic,Stain, Tissue,Stains, Tissue
D001647	Bile Acids and Salts	Steroid acids and salts. The primary bile acids are derived from cholesterol in the liver and usually conjugated with glycine or taurine. The secondary bile acids are further modified by bacteria in the intestine. They play an important role in the digestion and absorption of fat. They have also been used pharmacologically, especially in the treatment of gallstones.	Bile Acid,Bile Salt,Bile Salts,Bile Acids,Acid, Bile,Acids, Bile,Salt, Bile,Salts, Bile
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23
D012995	Solubility	The ability of a substance to be dissolved, i.e. to form a solution with another substance. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Solubilities
D012996	Solutions	The homogeneous mixtures formed by the mixing of a solid, liquid, or gaseous substance (solute) with a liquid (the solvent), from which the dissolved substances can be recovered by physical processes. (From Grant & Hackh's Chemical Dictionary, 5th ed)	Solution
D013329	Structure-Activity Relationship	The relationship between the chemical structure of a compound and its biological or pharmacological activity. Compounds are often classed together because they have structural characteristics in common including shape, size, stereochemical arrangement, and distribution of functional groups.	Relationship, Structure-Activity,Relationships, Structure-Activity,Structure Activity Relationship,Structure-Activity Relationships