Answer: GCI's OmicsLink™ Expression Clones are generated by its patented RecJoin™ cloning technology. By using this technology to construct a 5' tag-ORF fusion expression clone, there is no attB site between 5' tag and the start codon ATG of the full-length ORF. The extra 8 amino acids encoded by attB site in Invitrogen's pDEST expression clones will not be present in the proteins produced by using OmicsLink™ Expression clones. Same principle applies to 3' fusion protein production.