Biological transducers

Browner, M., and R. Fletterick. 1992. Phosphorylase a biological transducer. Trends Biochem. Sci. 17 66-71. 

Microfluidic Control Sequential and combinatorial delivery of signals to cells or tissue in microfluidic devices can be accomplished by using built-in control systems. Several microfluidic tools including valves, pumps, mixers, fluidic oscillators, fluidic diodes, etc. have been developed to accomplish fluidic control in these devices. These components can either be passive or active. Examples of passive elements include one-way valves (flap, ball) and hydrophobic patohes which take advantage of the interactiOTi between the chemical surface properties of the substrate and Uquid. Active elements, on the other hand, typically require some type of actuation mechanism. Several mechanisms for force transduction in microfluidic devices include mechanical, thermal, electrical, magnetic, and chemical actuation systems as well as the use of biological transducers. There has been a significant amount of work in this area that has been presented in a review by Erickson and Li [5]. 

Mueller and Rudin and Lev and Buzhinsky found, however, that valinomycin induced an increase in the ion permeability of black lipid membranes which obviously were free of all complicated biological transducers. An alternative mechanism was proposed to explain the activity of valinomycin in which it was suggested that valinomycin forms an ion conducting channel across the lipid bilayer This mechanism was rejected in favor of the currently accepted mobile carrier mechanism when it was demonstrated that both valinomycin and nigericin could transport ions across bulk phases too thick to accommodate stacked molecular channels The generic term ionophore, i.e. ion carrier, was chosen to describe these compounds by Pressman et al. in order to emphasize the dynamic aspects of the transport mechanism Although this term is widely accepted, Ovchinnikov... 

Green, D.E., Fleischer, S. On the molecular organization of biological transducing systems. In Horizons in biochemistry (Kasha, M., and Pullman, B., eds.), p. 381-420. New York Academic Press 1962... 

A major advance in force measurement was the development by Tabor, Win-terton and Israelachvili of a surface force apparatus (SFA) involving crossed cylinders coated with molecularly smooth cleaved mica sheets [11, 28]. A current version of an apparatus is shown in Fig. VI-4 from Ref. 29. The separation between surfaces is measured interferometrically to a precision of 0.1 nm the surfaces are driven together with piezoelectric transducers. The combination of a stiff double-cantilever spring with one of a number of measuring leaf springs provides force resolution down to 10 dyn (10 N). Since its development, several groups have used the SFA to measure the retarded and unretarded dispersion forces, electrostatic repulsions in a variety of electrolytes, structural and solvation forces (see below), and numerous studies of polymeric and biological systems. 

The presence of polymer, solvent, and ionic components in conducting polymers reminds one of the composition of the materials chosen by nature to produce muscles, neurons, and skin in living creatures. We will describe here some devices ready for commercial applications, such as artificial muscles, smart windows, or smart membranes other industrial products such as polymeric batteries or smart mirrors and processes and devices under development, such as biocompatible nervous system interfaces, smart membranes, and electron-ion transducers, all of them based on the electrochemical behavior of electrodes that are three dimensional at the molecular level. During the discussion we will emphasize the analogies between these electrochemical systems and analogous biological systems. Our aim is to introduce an electrochemistry for conducting polymers, and by extension, for any electrodic process where the structure of the electrode is taken into account. 

Blakesley VA, Butler AA, Koval AP, Okubo Y, LeRoith D 1999 IGF-I receptor function transducing the IGF-I signal into intracellular events. In RG Rosenfeld, CT Roberts (eds) The IGF system Molecular biology, physiology and clinical applications. Humana Press, New Jersey, p 143-163... 

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