The creation of smart materials is a current goal of many laboratories including our own. We are involved in studying a number of thin film and monolayer systems which share the common features of involving highly conjugated conducting organic polymers and the evolved properties of specific biological macromolecules. In this report we describe a generic ‘cassette’ methodology for immobilizing biotinylated biological macromolecules to hydrophobic surfaces using a novel class of conducting copolymers of polythiophene. These copolymers are derivatized with long alkyl chains and biotin moieties to bind, respectively, to the hydrophobic surface and the biotinylated species, through the biotin - streptavidin interaction. We utilize the monolayer ‘cassette’ approach to attach a signal transducing biomolecule alkaline phosphatase to the surface of a glass capillary. This produces a flexible system in which chemiluminescence provides the basis for a useful measurement strategy. A novel technique involving the generation of chemiluminescence signal from alkaline phosphatase catalyzed dephosphorylation of a macrocyclic phosphate compound is described. Detection of paraoxon and methyl parathion, both enzyme inhibitors, has been achieved at ppb levels. The technique is rapid, sensitive, and is applicable to the detection of all organophosphorus based insecticides. The technique will be used in developing a fiber;optic biosensor for remote detection of insecticides.

The biophysics of energy converting model proteins is presented as a general set of three postulates with fifteen corollaries for fifteen subtypes of molecular machines. All of the molecular machines utilize a common structural transition, an inverse temperature transition characterized by increased hydrophobic folding and/or assembly as the temperature is increased through a transition temperature range identified by Tt. These molecular machines, which can be polymers (e.g., proteins or protein-based polymers), are capable of interconverting the free energies involving the six intensive variables of mechanical force, temperature, pressure, chemical potential, electrochemical potential, and electromagnetic radiation.

First-order molecular machines of the Tt-type are molecular engines which, with the appropriate energy input, can result in the production of useful mechanical motion. Postulate I is for the thermally-driven molecular engine. Postulate II with four corollaries is for the four cases where the energy inputs drive hydrophobic folding by lowering the temperature, Tt, at which the inverse temperature transition occurs. This is called the ΔTt-mechanism. The four energy inputs that have been shown to change the value of Tt are due to changes (1) in concentrations of chemicals, (2) in oxidative state of attached prosthetic groups, (3) in pressure, and (4) resulting from the absorption of light by attached chromophores. Postulate III with ten corollaries are for the ten pairwise energy conversions involving the intensive variables listed above exclusive of mechanical force. These energy conversions utilize the hydrophobic association transition but do not result in the motion implicit in the folding or assembly process. These are second-order molecular machines of the Tt-type.

The physical basis for the ΔTt-mechanism of energy conversion of Postulates II and III is proposed to arise due to competition for hydration between apolar (hydrophobic) and polar moieties. This competition is capable of effecting large changes in pKa values of Glu, Asp, Lys and His residues. This mechanism is proposed to be a dominant process in protein folding, assembly, and function.

A bilayer device: consisting of a conducting, flexible polypyrrole layer and an adherent, elastic non conducting film was constructed. One end of the bilayer was fixed with a clamp, allowing the electrical contact with polypyrrole. Polypyrrole volume increases and decreases reversibly during electrochemical oxidation and reduction processes in aqueous solutions. Reversible stress gradient across the flexible film promotes reversible angular movements of the free end of the bilayer, around the fixed end. The effect of the anodic and cathodic potential gradients, as well as the effect of the concentration of movable ions on a 180° angular movement, in the electrolytic solution, were studied. Weights of 1000 times the bilayer weight adhered at the bottom of the bilayer were reversibly trailed across 180° by electrochemically controlled oxidation and reduction processes, in a few seconds. As an electric current promotes chemical reactions giving a change of volume and promoting a mechanical energy, the device was named artificial muscle. Similarities and differences between muscles and artificial muscles are discused.