Phospholipids chiral at phosphorus: Fourier-transform infrared study on the gel-liquid crystalline transition of chiral thiophosphatidylcholine

Abstract

Fourier-transform infrared spectroscopy (FT-IR) was used to study the structural properties of Rp, Sp, and Rp + Sp isomers of 1,2-dipalmitoyl-sn-glycero-3-thiophosphocholine (DPPsC), in comparison with those of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). For the vibrational modes of acyl chains, isomers of DPPsC show similar temperature and phase dependence to DPPC. However, the Rp isomer of DPPsC exhibits several unique properties: the CH2 symmetric stretching band is unusually weak, the CH2 asymmetric stretching band is unusually narrow, and the CH2 wagging bands do not disappear completely at temperatures above the main transition. These differences could imply a tighter packing and be responsible for the unique phase-transition property of (Rp)-DPPsC. For the vibrational modes of the thiophosphodiester group, the frequency of the P-O stretching mode of DPPsC suggests that the POS- triad exists predominantly in the mesomeric form. This is in contrast to the structure of nucleoside phosphorothioates where charge localization at sulfur has been demonstrated [Iyengar, R., Eckstein, F., & Frey, P. A. (1984) J. Am. Chem. Soc. 106, 8309-8310]. This suggests that the different biophysical properties between isomers of DPPsC are not due to different charge distribution in the POS- triad or different geometry of charge distribution on the membrane surface. Instead, factors such as size or hydration property of oxygen and sulfur, as well as the different configuration at phosphorus, could be responsible for the differences in the conformation and packing of acyl chains, as revealed by the different properties in the CH2 stretching and wagging modes of DPPsC.

Phosphorothioate cap analogs stabilize mRNA and increase translational efficiency in mammalian cells

“…Although sulfur substitution for oxygen is considered conservative because the van der Waals radius, P-S bond length (Liang and Allen 1987), and anionic character of parent and modified oligonucleotides are all very similar (Frey and Sammons 1985;Chang et al 1986), there are nonetheless important differences between phosphate and phosphorothioate groups, including the existence of diastereoisomers. Interestingly, these isomers can exhibit different sensitivities to nucleases.…”

Characterization of Dipalmitoylphosphatidylcholine Liposomes Containing a Soybean-Derived Sterylglucoside Mixture by Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy, and Enzymatic Assay

“…The effect of the concentration of SG in DPPC/ SG-liposomes (7:2, 7:3.5, 7:7) on IR spectra over the 2000-800 cm -1 range is shown in Figure 6, and the frequencies of the selected absorption bands are summarized in Table 1. 21,22 Asymmetric and symmetric stretching bands of DPPC phosphate in liposomes were noticed at 1228.4 and 1086.6 cm -1 , respectively. The most dominant features in the 1350-800 cm -1 region are due to the vibrations of the phosphate moiety.…”

Chiral Phosphorothioates: Stereochemical Analysis of Enzymatic Substitution at Phosphorus

“…It was thereby shown that phospholipase A2 preferentially accepts (R,)-DPP,E as a substrate, whereas phospholipase C accepts (S,)-DPP,E. The chiral thiophospholipids have been used for analysis of the stereochemical course of phosphotransferase action by phospholipase D, as well as for comparative studies of their different properties in various physical states (57)(58)(59).…”