Your motherboard supports upto 16GB DDR3 memory in 4 slots as (1*4, 4*4, 2*4, 2*2, 4*2 and so on...) It has got a dual channel architecture (2 different colors for 4 RAM slots) but it specifies DRAM size as 1/2/4 GB...
U cannot use 1 8GB stick, but it will be faster if you use (4*2)GB on similiar colored slots...