What are MIPS ?

Plastics are an increasingly common part of everyday life. Most of what we consider to be plastics are carbon based (chemists say, "organic") polymers. Organic polymers are long chains, or networks, of small carbon compounds linked together to form long heavy molecules, or macromolecules. The familiar "plastics" are typically polymers that are formed in the absence of a solvent, by a method called bulk polymerization. Bulk polymerization results in masses of entwined or networked strands to form a solid substance. The rigidity of the solid can be controlled by a process known as "crosslinking". Crosslinking is obtained when one of the building blocks of the polymer (a monomer) has the ability to tie two or more of the strands together. The addition of crosslinking monomers forms a three dimensional network polymer that is more rigid than an uncrosslinked polymer and is insoluble in organic solvents. The greater the proportion of crosslinking monomer, the harder, or more rigid, the resulting plastic.

Polymers are common in nature and provide many of the structural molecules in living organisms. Many of the natural polymers, such as cellulose, chitin and rubber, have been employed by man to make fabrics and to use as structural materials. Some natural polymers, like rubber, are being supplanted by a large variety of synthetic polymers. An understanding of polymer structure and composition has allowed chemists to make polymers with specific desired physical properties. This is the reason why synthetic polymers have in many cases replaced other materials and natural polymers. Synthetic polymers can be made more durable and longer lasting. Their specific properties can be tailored to a purpose and so, as in the case of natural rubber, synthetic polymers can be produced that are vast improvements to their natural counterparts.

A fairly recent direction in synthetic polymer development is the introduction of molecular imprinted polymers (MIPs). These materials trace their origin back to suppositions about the operation of the human immune system by Stuart Mudd in the 30's and Linus Pauling in the 40's. Mudd's contribution was to propose the idea of complementary structures. That is to say the reason a specific antibody attacks a specific target or "antigen", is because the shape of the antibody provides an excellent fitting cavity for the shape of the antigen. This description is very similar to the "lock and key" analogy used to explain the action of enzymes, the molecules responsible for hastening and directing biochemical reactions. In this case, the enzyme forms the lock for a particular chemical key to fit, and as this "key" is turned, the enzyme directs and hastens the production of desired products from the chemical target.

Pauling's contribution to the development of MIPs was to explain the source of the complementary shape exhibited by antibodies. He postulated how an otherwise non-specific antibody molecule could be re-organized into a specific binding molecule. He reasoned that shape specificity was obtained by using the target antigen to arrange the complementary shape of the antibody. Thus a nonspecific molecule shapes itself to the contours of a specific target and, when the target is removed, the shape is maintained to give the antibody a propensity to rebind the antigen. This process is now known as molecular imprinting or "templating".