Using a vacuum sealer to marinate?
This works by increasing the porousness of the meat inside the bag. When a vacuum is created, there is a natural tendency for matter to occupy that space. It does this by increasing the amount of space between particles, otherwise known as density. This increases the size of the microscopic holes in the meat, and thus effectively increases the surface area in which the marinade can contact the meat. More surface area means by marinade sticks to your food.

If you'd like to see the effects of vacuum pressure on foods greatly exagerrated, put a marshmallow in a vacuum seal bag and see what happens. :-)