Nanoscope 4 afm

The influence of Mag2 or Mag-A on the morphology of DMPC and DMPC/DMPG (4:1) bilayers were examined by a Nanoscope IV AFM with a Multimode head (Veeco, Santa Barbara, CA, USA) using a vertical engage ‘E' scanner. Images were obtained in 20 mM phosphate buffer pH 7.4 via taping mode with NSC-36 ‘B' silicon cantilevers (Micromasch, Tallinn, Estonia) with a nominal force constant of 1.75 N/m. 20 µl of freshly prepared liposome (50 nm) solution was deposited onto freshly cleaved mica and incubated at 40°C for 30 min. After incubation, the surface was rinsed 3 times with buffer at 25°C. The bilayers were then imaged in buffer using the liquid cell with several additions of 15 µl of 10 µM peptide over the supported bilayers. Topographic, phase and amplitude images at a resolution of 512 × 512 were simultaneously obtained using scan frequencies between 0.5–1.5 Hz with typical scan sizes of 5 µm × 5 µm, 2 µm × 2 µm, 1 µm × 1 µm or 500 nm × 500 nm. Minimal force (free oscillating amplitude ~20 nm, setpoint of 60–80%) was used to reduce the mechanical agitation inflicted on the sample. Images were processed with a sequence of plane fitting and offset flattening using either WSxM 4.0 (www.nanotec.es) or Gwyddion 2.29 (www.gwyddion.net) software.