Bile acids (BAs) are facial amphiphiles synthesized in the body of all vertebrates. They undergo the enterohepatic circulation: they are produced in the liver, stored in the gallbladder, released in the intestine, taken into the bloodstream and lastly re-absorbed in the liver. During this pathway, BAs are modified in their molecular structure by the action of enzymes and bacteria. Such transformations allow them to acquire the chemical–physical properties needed for fulling several activities including metabolic regulation, antimicrobial functions and solubilization of lipids in digestion. The versatility of BAs in the physiological functions has inspired their use in many bio-applications, making them important tools for active molecule delivery, metabolic disease treatments and emulsification processes in food and drug industries. Moreover, moving over the borders of the biological field, BAs have been largely investigated as building blocks for the construction of supramolecular aggregates having peculiar structural, mechanical, chemical and optical properties. The review starts with a biological analysis of the BAs functions before progressively switching to a general overview of BAs in pharmacology and medicine applications. Lastly the focus moves to the BAs use in material science.

A structural comparison between the Normal and the Expanded isomers of the human serum albumin has been carried out by using small angle X-ray scattering (SAXS) and light scattering (LS) techniques. Geometrical bodies, recovered structures (GA_STRUCT code) and rigid body modeling (CRYSOL and BUNCH software) were used to obtain low-resolution 3D structures from one-dimensional scattering patterns. These restored shapes were also exploited to perform a correlation between SAXS and LS data. By attempting a detailed description of globular and unfolded protein structures in solution, we tried to propose a suitable approach to follow the path of folding/unfolding processes and to isolate and characterize possible partially folded intermediate states.