Spin-Labeled Ibuprofen in Lipid Bilayers. MD Simulations

Ibuprofen is a widely used nonsteroidal anti-inflammatory drug. However, it has side effects that may be related to the influence of ibuprofen on the lipid component of cell membranes. Therefore, the behavior of ibuprofen in lipid bilayers has been widely investigated using various methods. Information on the location of ibuprofen in membranes are obtained using magnetic resonance spectroscopy with spin-labelled ibuprofen molecules. However, the question remains whether the results obtained are consistent with those corresponding to unlabeled ibuprofen? Using molecular dynamics (MD) simulations, we make such a comparison for ibuprofen with the spin label TEMPOL in a POPC bilayer, both in its pure form and in the presence of 20% cholesterol. We show that at relatively low concentrations, around 3% Drug/Lipid ratio, and a temperature of 310 K, the spin label has little effect on the distribution of ibuprofen in the bilayer, despite its relatively large size and ability to form additional hydrogen bonds.