sentences:  Several plasmid vectors were developed to facilitate the expression and purification of such fusion proteins.When the recombinant MBP includes a signal peptide, the fusion protein can be exported into the periplasmic space, which facilitate its purification since the periplasmic fluid contains only a limited number of proteins and can be recovered either by an osmotic shock or by permeabilization of the outer membrane with antibiotics, e.g.Polymyxin B Sulfate.