Membrane fluidity response to odorants as seen by H-2-NMR and infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) and deuterium nuclear magnetic resonance spectroscopy (H-2-NMR) have been used to study the location of two odorants, beta-ionone and menthone, in a model membrane of dimyristoylphosphatidylcholine, as well as the effect of the odorants on the structure and dynamics of the phospholipids. The interaction has been investigated for two lipid-to-odorant molar ratios, 10:1 and 1:1. The two odorants were found to affect the fluidity of the membrane. More specifically, the H-2-NMR results indicate that at a lipid-to-odorant molar ratio of 10:1, both beta-ionone and menthone increase the order of the deuterons in the interfacial and headgroup regions of the lipid while the incorporation of the odorants at a lipid-to-odorant molar ratio of 1:1 decreases the order of both the lipid headgroup and acyl chains. On the other hand, the infrared results show that the incorporation of beta-ionone and menthone decreases the phase transition temperature and cooperativity of the lipid acyl chains. The results suggest that the site of incorporation of beta-ionone and menthone is very similar in DMPC membranes.