Capsaicin Fluidifies the Membrane and Localizes Itself near the Lipid-Water Interface.

Capsaicin is the chemical responsible for making some peppers spicy hot, but additionally it is used as a pharmaceutical to alleviate different pain conditions. Capsaicin binds to the vanilloid receptor TRPV1, which plays a role in coordinating chemical and physical painful stimuli. A number of reports have also shown that capsaicin inserts in membranes and its capacity to modify them may be part of its molecular mode of action, affecting the activity of other membrane proteins. We have used differential scanning calorimetry, X-ray diffraction, 31P NMR, and 2H NMR spectroscopy to show that capsaicin increases the fluidity and disorder of 1,2-palmitoyl-sn-glycero-3-phosphocholine membrane models. By using 1H NOESY MAS NMR based on proton–proton cross-peaks between capsaicin and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine resonances, we determined the location profile of this molecule in a fluid membrane concluding that it occupies the upper part of the phospholipid monolayer, between the lipid–water i...