hello everybody- i have problem with PCR

[farshadsha]

hello,
it is first post of me!
i am student of biotechnology, in this cours we want ligate the gene of ADE1 to onetype of yeast (saccharo mysis). we have used two different presedure. first we design the restriction site ourselves and the second we tried to find the rstriction site in the original fragment. the fragment of first presedure was around 1220 units and all PCR steps was OK . in the second presedure the fragment was around 4500 units.
but wat is the problem?
in the second presedure becouse of lenght of fragment we have used the long chain presedure in PCR but we had not any result, we changed the anealing time and tempreture and touch down also but there was not any result, more than 10 tiems and in 3 different type of PCR, BUT we could not. if here any body is intreseted to help me i can send y protocol and report, i am so intrested to solv this problem.
tnx.