Transmembrane transport physiologically active

Pillararenes (PA), a new kind of paracyclophane, were first synthesized in 2008 as pillar[5]arene (PA[5]) and were recognized as a new generation of supramolecular host because of their unique pillar structural feature, nanometer-sized (<1.0nm) cavity, and multiple fiinctionalizable sites. In the last few years, these new types of compound have shown biomedical applications in the construction of artificial channels for transmembrane transport of physiologically active solutes and vesicles for drug delivery, which will be reviewed in this chapter. 

This results in the extrusion of three positive charges for every two that enter the cell, resulting in a transmembrane potential of 50-70 mV, and has enormous physiological significance. More than one-third of the ATP utilized by resting mammalian cells is used to maintain the intracellular Na+-K+ gradient (in nerve cells this can rise up to 70%), which controls cell volume, allows neurons and muscle cells to be electrically excitable, and also drives the active transport of sugars and amino acids (see later). 

Membrane phenomena cover an extremely broad field. Membranes are organized structures especially designed to perform several specific functions. They act as a barrier in living organisms to separate two regions, and they must be able to control the transport of matter. Moreover, alteration in transmembrane potentials can have a profound effect on key physiological processes such as muscle contraction and neuronal activity. In 1875, Gibbs stated the thermodynamic relations that form the basis of membrane equilibria. The theory of ionic membrane equilibrium was developed later by Donnan (1911). From theoretical considerations, Donnan obtained an expression for the electric potential difference, commonly known as the membrane potential between two phases. 

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