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Updated: Apr 9, 2026

Quantitative and Qualitative Method for Sphingomyelin by LC-MS Using Two Stable Isotopically Labeled Sphingomyelin Species
Published on: May 7, 2018
Orientation and Order of the Amide Group of Sphingomyelin in Bilayers Determined by Solid-State NMR
Nobuaki Matsumori1, Toshiyuki Yamaguchi2, Yoshiko Maeta1
1Department of Chemistry, Graduate School of Science, Osaka University, Osaka, Japan.
Abstract:
Sphingomyelin (SM) and cholesterol (Chol) are considered essential for the formation of lipid rafts; however, the types of molecular interactions involved in this process, such as intermolecular hydrogen bonding, are not well understood. Since, unlike other phospholipids, SM is characterized by the presence of an amide group, it is essential to determine the orientation of the amide and its order in the lipid bilayers to understand the nature of the hydrogen bonds in lipid rafts. For this study, 1'-(13)C-2-(15)N-labeled and 2'-(13)C-2-(15)N-labeled SMs were prepared, and the rotational-axis direction and order parameters of the SM amide in bilayers were determined based on (13)C and (15)N chemical-shift anisotropies and intramolecular (13)C-(15)N dipole coupling constants. Results revealed that the amide orientation was minimally affected by Chol, whereas the order was enhanced significantly in its presence. Thus, Chol likely promotes the formation of an intermolecular hydrogen-bond network involving the SM amide without significantly changing its orientation, providing a higher order to the SM amide. To our knowledge, this study offers new insight into the significance of the SM amide orientation with regard to molecular recognition in lipid rafts, and therefore provides a deeper understanding of the mechanism of their formation.
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