cat biting and holding down other cat by neck

I have 2 cats that came from the same home but I got at different times. Beezle ( neutered) is now about 12 pounds and Big ( unneutered)is about 17 pounds. They have lived in different parts of the house because Big is being quarantined until we know if he has feline leukemia. Every once in a while Beezle will get through and Big will take him down like a gazelle.he'll pin him to the ground by the back of his neck Every time. If they ever get a chance to be together is there away to stop this? They use to be friends in there old home. I'll also have Big neutered by then as well. He also likes to bite me which will be another thread. What a beast. Thanks

Big is trying to breed Beezle!!  That's what male cats do before they are neutered (and even afterwards sometimes!)  You need to keep them totally separate and get Big neutered before you re-introduce them, and then you should introduce them slowly as it takes some time for the neutered cat to lower his testosterone level.  We have an article on proper introductions, and Jackson Galaxy has a good video on it as well. 

http://www.thecatsite.com/a/introducing-cats-to-cats