EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">I am currently trying to get good transfection efficiency after infection of the bone marrow cells with the ecotropic murine stem cell retrovirus (MSCV). In brief, I have transfected my ecotropic virus (MSCV) into 293T cells and tested for GFP expression after growing then in NIH3T3 cells. Luckily, I got 90-95 % positive for GFP, analyzed by FACS. However, when the same virus is transduced into primary bone marrow cells by spinfection at 2000 rpm for 1.5 h, I am only getting 7% positive for GFP. As this is the first time trying to transduce BM cells, I'm unable to increase the transfection efficiency. Please give me some suggestions which might help.