Micelle formation of bile salts and zwitterionic derivative as studied by two-dimensional NMR spectroscopy.
The self-association of sodium taurodeoxycholate (NaTDC) and a zwitterionic derivative of cholic acid (CHAPS) in deuterium oxide was investigated by one- and two-dimensional nuclear magnetic resonance spectroscopy (NMR) spectroscopy. Analysis of the concentration dependence of the chemical shifts of several protons suggested that NaTDC and CHAPS form nonamers and heptamers, respectively, as well as dimer. The equilibrium constants of dimerization and the micellar aggregation numbers are close to the literature values. From the intensities of intermolecular cross-peaks in the nuclear Overhauser effect spectroscopy (NOESY) and rotating frame nuclear Overhauser effect spectroscopy (ROESY) spectra of NaTDC and CHAPS micellar solutions, partial structures of their micelles were estimated. The CHAPS micelle consists mainly of the back-to-back association, similarly to taurocholate (NaTC). However, the NaTDC micelle consists of the back-to-face association, because the face of NaTDC is rather hydrophobic. Furthermore, the back of bile molecules forms a convex plane and the face forms a concave plane. The back-to-face structure of NaTDC will be stabilized by a close contact between these planes. The chemical shift changes of several protons of CHAPS and NaTC in the micellar state are close to each other, but are different from those of NaTDC. This finding is consistent with the difference in their micellar structures.
Funasaki
Noriaki
N
Department of Physical Chemistry and 21st Century COE Program, Kyoto Pharmaceutical University, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan. funasaki@mb.kyoto-phu.ac.jp
Fukuba
Makoto
M
Hattori
Takashi
T
Ishikawa
Seiji
S
Okuno
Takashi
T
Hirota
Shun
S
D001647:Bile Acids and Salts / Q000737:chemistry* / Q000378:metabolism; D002793:Cholic Acids / Q000737:chemistry; D003902:Detergents / Q000737:chemistry*; D017666:Deuterium Oxide / Q000737:chemistry; D004058:Diffusion; D057927:Hydrophobic and Hydrophilic Interactions; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008823:Micelles; D008958:Models, Molecular; D011522:Protons; D013657:Taurodeoxycholic Acid / Q000737:chemistry
D001647:Bile Acids and Salts; D002793:Cholic Acids; D003902:Detergents; D008823:Micelles; D011522:Protons; D013657:Taurodeoxycholic Acid; D017666:Deuterium Oxide; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate