title: A model for micellar aggregates of a bile salt: crystal structure of sodium taurodeoxycholate monohydrate.
abstract: Crystals of sodium taurodeoxycholate monohydrate, NaC26H44NO6S X H2O, are trigonal, space group P3(1), with a = 18.393(1), c = 7.097(1)A, V = 2079.3(5)A3, and Z = 3. The structure was solved by direct methods and Fourier techniques and refined by full-matrix least-squares calculations. The final R index is 0.051. The side chair of the anion displays an approximate folded-back conformation. The cyclopentane ring assumes an intermediate conformation between the half-chain and the beta-envelope. The sodium ion shows a distorted octahedral coordination with six oxygen atoms, giving rise to ion-ion and ion-dipole interactions. The molecules form helices, characterized by threefold screw axes, with a radius of about 16 A. The helices are packed in such a way as to be embedded in each other as cog-wheels. The helix found in this crystal structure will be used as a model and checked in the study of the micellar solutions of sodium taurodeoxycholate, following the same strategy satisfactorily employed in the case of sodium deoxycholate.
mesh_terms: D001647:Bile Acids and Salts / Q000032:analysis*; D003460:Crystallization; D003840:Deoxycholic Acid / Q000031:analogs & derivatives*; D008823:Micelles; D008956:Models, Chemical; D008968:Molecular Conformation; D013657:Taurodeoxycholic Acid / Q000032:analysis*
chemical_list: D001647:Bile Acids and Salts; D008823:Micelles; D003840:Deoxycholic Acid; D013657:Taurodeoxycholic Acid