A DFT study of infrared spectrum of sphingomyelin lipid molecule with calcium cation

Abstract

ABSTRACT:One of the phospholipids, sphingomyelin (SM) is the most abundant component of mammalian membranes in brain and nervous tissues. It plays an important role for apoptosis, aging, and signal transduction with cations. Recently, Yappert and co-workers have shown that human lens sphingomyelin and its hydrogenated derivative, dihydrosphingomyelin (DHSM) are interacted with Ca 2+ ions to develop human cataracts. In this study, we investigate conformational differences between an isolated SM/DHSM molecule and Ca 2+ -coordinated form by using density functional theory (DFT) calculations. B3LYP functional and 6-31G(d, p) double-ζ split-valence basis set is used for geometry optimization and normal mode analysis. One of resultant conformers of SMs has hydrogen bonding between hydroxyl and phosphate group, whereas another conformer has hydrogen bonding between hydroxyl and amide group. The red shift of calculated vibrational frequencies of amide band due to Ca 2+ is compared with experimental infrared spectrum. Finally, we discuss the Ca 2+ -induced effects from conformational and spectroscopic point of view to compare the experimental results.

Ab initio and DFT study of 31P‐NMR chemical shifts of sphingomyelin and dihydrosphingomyelin lipid molecule

“…The conformer 2 and 2′ have the same tendency with respect to Δδ. It suggests that 2 and 2′ is the candidate conformer as same as the conclusion of theoretical IR study 14 and experimental NMR studies 5, 9.…”

“…Table I shows the calculated 31 P‐NMR shielding constants and chemical shifts carried out by GIAO/B3LYP/6‐311+G(2d,p) using two types of stable structure of the previous study 14. Models 1 2 and 1′ 2′ mean the conformers of SM and DHSM, respectively.…”

“…Besides, the C2 and C3 of sphingosine have different stereo‐chemical conformations, however, 2 S, 3 R (or D ‐ erythro ) has been determined by NMR studies 5, 9, 12, 13. Starting from such conformation with a truncated model including the head and the interface region as shown in Figure 1, we have obtained two types of theoretically optimized structures by using DFT calculations 14. The resultant two stable structures of isolated model have different intramolecular hydrogen bonding and interact with calcium cation on different site.…”

“…First, using previously optimized structures of the truncated model of SMs and DHSMs 14, we calculate 31 P‐NMR shielding constant by GIAO/HF/6‐311+G(2d,p) and GIAO/B3LYP/6‐311+G(2d,p) method implemented in Gaussian 03. We also calculate 31 P‐NMR shielding constant of H 3 PO 4 as the reference of chemical shift, hence the 31 P‐NMR chemical shifts are obtained by where σ denotes the absolute isotropic value of 31 P‐NMR shielding tensor as the average of σ i ( i = xx, yy, zz ).…”

Specific Far Infrared Spectroscopic Properties of Phospholipids

“…Sphingomyelin (SM) belongs to the sphingolipid group and it is at the same time the most abundant component of mammalian membranes in brain and nervous tissues. It plays an important role for apoptosis, aging, and signal transduction with cations [6]. Phosphatidylethanolamine (PE) is ubiquitous in eukaryotic cell membranes, being unevenly distributed between the inner and the outer leaflets of the bilayer.…”