Study on the actin assembly on different substrates

The assembly processes of actin on mica substrate and lipid membrane by real time imaging of atomic force microscope (AFM) and laser scanning confocal microscope were studied. It was found that on the bare mica substrate, the small amount of G-actin nucleating points formed and subsequently self-assembled into long actin filaments with lengths up to tens of micro-meters. While on the positively-charged lipid membrane (DPPC : DPTAP = 4 : 1), large amounts of nucleating points quickly formed, leading to the formation of relatively shorter filaments. The proposed optimum condition for exploring actin assembly process with AFM in vitro is positively-charged substrates should be used while the AFM imaging force should be lower than 50 pN. These results laid foundation for construction of micro- and nano-scale transport systems based on actin. (authors)