Figure 1.

Effect of serotonin on the mechanical properties of PPC111 bilayer probed by different biophysical techniques. (A) Schematic of the AFM force indentation studies. (B) A representative histogram of breakthrough forces on the PPC111 bilayer in the absence (black) and presence (red) of 5 mM serotonin (reproduced from Dey et al. (25)). (C) Schematic of the fluorescence spectral properties of Nile Red in different membrane environments. (D) Fluorescence spectra of membrane-bound Nile Red dye in PPC111 bilayer in the absence (black) and presence (red) of 5 mM serotonin (average of N = 3 measurements). (E–G, I, and J) Calculation of the generalized polarization (GP) of Laurdan in supported phase-separated model membrane DEC221. (E) and (I) are images recorded in the green and blue regions. (F) and (J) are the images obtained with the indicated formula to generate images 3 and 4. (G) The GP image. (K) Schematic of the fluorescence spectral properties of Laurdan in ordered and disordered membrane environments. (H) Representative GP image of PPC111 SLB. (L) Representative GP image of PPC111 SLB in the presence of 5 mM serotonin. Scale bar: 10 μm. (M) GP value of Laurdan dye in the PPC111 bilayer in the absence (black) and presence (red) of 5 mM serotonin (average of N = 3 measurements). (N and O) Changes in the rotational anisotropy of DPH and TMA-DPH dyes in the PPC111 SLB with increasing concentrations of serotonin probed by steady-state anisotropy experiments. (P) A representative Raman spectrum (normalized at 2885 cm⁻¹) of the PPC111 SLB in the absence (black) and presence (light brown) of 20 mM serotonin. (Q) Relative change in the mean value of I₂₈₈₂/I₂₈₄₅ and I₂₈₄₅/I₂₉₂₃ of PPC111 bilayer in the presence of 20 mM serotonin (average of N = 5 measurements). (R) ²H NMR order parameter along the deuterated lipid chains for POPC-d₃₁ and POPG-d₃₁ in the absence and presence of 10 mol % serotonin at 25°C (reproduced from Dey et al. (25)). Error bar represents mean ± SE.