Associated membrane protein types are lipopolysaccharide selective barriers. Biological membranes include cell membranes, outer coverings of cells or organelles that allow passage of certain proteins and nuclear membranes, which cover a cell nucleus; and tissue membranes, such as mucosae and serosae. ,Rhesus Monkeys proteins are often measured by ELISA on serum or plasma since consensus epitopes with the human ELISA are used for producing the antibodies of these ELISA test kits. Often cDNA of monkeys is used as alternative to human cDNA as a model for drug development. Monkeys are generally considered to be intelligent, particularly Old World monkeys.