Figure 3.
Histograms of tip-lipid bilayer pull-out forces of RLPs with different SM concentration in dependence to NO treatment. Force data of untreated RLP (left column), RLP post 1 μM (middle column) and post 5 μM NO treatment (right column) are shown. In each row, RLP with the same composition are shown. Untreated RLP show increase in pull-out forces at the largest SM concentration (A–C, left) which indicates reduced membrane permeability. Addition of 1 μM NO to 2:0:1 (POPC:SM:CH) ratio caused the force spectrum to broaden (A, middle) compared with control (A, left), with maxima forces at 0.85 and 1.21 nN. At 5 μM, the maxima forces increased further to 1.74 and 2.05 nN (A, right). For 2:1:1 (POPC:SM:CH) ratio, a competitive behavior is observed and after NO treatment (at 1 and 5 μM), the pull-out forces (B, middle and right) were similar to untreated 2:1:1 (POPC:SM:CH) ratio. This indicates presence of possible critical concentration in maintaining membrane integrity. At 2:2:1 (POPC:SM:CH) ratio, detrimental effect of NO is observed (C, middle and right) with decrease in pull-out forces compared with control (C, left), indicating membrane destruction. Histograms represent force data of only tip-membrane interactions and tip-mica forces are excluded. To see this figure in color, go online.