Unless your plasmid is very large (like a cosmid) I think you have very little plasmid DNA, the strong band you are seeing near the top is most likely genomic DNA. So upon cutting it will not produce a band but a faint smear of many bands. There might be a hint of plasmid in lane 3 but its very faint.

Hi Mr. Benedik,

Thank you for your answer. Actually, we think that these faint smear of many bands are different forms of plasmid such as supercoiled, linear and circular forms. Our plasmids have 5000 bp of sizes. You may be right about bands of the top that can be genomic DNA