(1)H and (13)C NMR chemical shifts of methacrylate molecules associated with DMPC and/or DPPC liposomes

Abstract

In the light of recent developments, changes in (1)H and (13)C NMR chemical shifts of methacrylate molecule associated with DMPC (L-alpha dimyristoylphosphatidylcholine) or DPPC (L-alpha-dipalmitoylphosphatidylcholine) liposomes as a model for mimic native lipid bilayers were studied at 30, 37, and 52 degrees C. The chemical shifts of 3Ha, 3C, and 4C resonances in methacrylates (see Fig. 2) were greatly shifted higher field, suggesting the methacrylate molecule-lipid bilayer interaction. Comparison of the findings with methyl methacrylate (MMA), ethylene dimethacrylate (EDMA), and triethyleneglycol dimethacrylate (TEGDMA) revealed that the interaction of dimethacrylates (EDMA, TEGDMA) was greater than monomethacrylate, MMA. Their interaction with DMPC liposomes was also judged by a differential scanning calorimetry (DSC), indicating that the interaction was characterized by decreasing the enthalpy, entropy, and transition co-operativity. The evidence of the upfield NMR-shifts for methacrylate molecules was also judged by the descriptors such as the reactivity (HOMO-LUMO energy) and the electrostatic function (partial charges) between methacrylate molecules and DPPC, calculated by a PM 3 semiempirical MO method. The upfield NMR shifts were considerably well interpreted from the descriptors. NMR screening technique in methacrylates to phospholipid targets would be highly valuable in biomaterial developments. Figure 2 Changes in (1)H and (13)C NMR chemical shifts of methacrylate molecule associated with DMPC or DPPC liposomes. DMPC liposomes/MMA (1:1, molar ratio) and DMPC/TEGDMA (1:1) liposomes were measured at 30 degrees C. In DPPC liposome system, the rippled gel phase was measured at 30 degrees C, whereas the liquid crystalline phase for MMA and for both EDMA and TEGDMA were measured at 52 degrees C and 37 degrees C, respectively.