Transfection of Lip/M-VLP at (a) 10 μg/109 M-VLPs Lip587/M-VLP, (b) 10 μg/109 M-VLPs Lip505/M-VLP, (c) 10 μg/109 M-VLPs Lip550/M-VLP at 4 °C and 37 °C. Cells were incubated with hybrid vectors at 4 °C or 37 °C for 4 h after which the vectors were removed and replaced with fresh media, and the cells were incubated at 37 °C for the remainder of the experiment. Luciferase activity (RLU/mg total protein) was normalized to the corresponding values 48 h post-transfection at 37 °C. Cellular uptake of Lip/M-VLP at (d) 10 μg/109 M-VLPs Lip587/M-VLP, (e) 10 μg/109 M-VLPs Lip505/M-VLP and (f) 10 μg/109 M-VLPs Lip550/M-VLP at 4 °C and 37 °C for 4 h as with the transfections. Uptake of Chi/M-VLP was normalized to the corresponding values 8 h post-transfection at 37 °C. Error bars represent SD, n=3.