Reversible molecular adsorption as a tool to observe to perform of heteropolymer gels

Protein folding is one of the most challenging problems in science. How can polymers memorize and fold into unique conformations? How can they recognize molecules, catalyze chemical reactions, transfer molecular information, and create motions? The principle behind these mechanisms lies in the concept of thermodynamically stable phases of heteropolymers. Recent theories predict that the collapsed phase should be further classified into three phases: freely fluctuating like liquid, frozen in degenerate conformations, and frozen in a unique conformation. This yields a clue on how one can attempt creation artificial polymers capable to mimic some of the protein properties and functions. The reversible adsorption of target molecules is suggested as a primary means to achieve this goal. Target molecules with multiple adsorption sites play a twofold role. First, they mediate specific interactions between monomers and thus serve as "gluons". Second, monitoring the adsorption provides the experimental possibility to test directly on monomer contacts, which is directly related to observation of the order parameter associated with heteropolymer freezing transition. A slight change in the backbone conformation alters the spacial arrangement of the group, allowing for reversible adsorption and release. Polymer gels are developed that can reversibly change their affinity to target molecules by orders of magnitude. The gels are made of copolymers of backbone monomers that can reorganize themselves through thermal volume phase transition and of monomers that can attract the target at multiple contact points. Further the gels "imprinted" with the target showed a marked increase in the affinity, thus mimicing a protein-like ability to memorize and recognize certain target.