Transport overshoot phenomenon

Sevastianov et al.73,74) have developed a model which considers the effect of surface heterogeniety on the adsorption process. They define centers of irreversible adsorption , labeled P, and centers of irreversible desorption , labeled D. They argue, in agreement with Soderquist and Walton, that desorbed material is conformationally altered and thus cannot readsorb — hence desorption is irreversible. The results of this model are given as Fig. 14, taken from Ref. 7J). The model also includes the case where adsorption may be transport limited. The model fits commonly observed adsorption data, including the overshoot phenomenon (Fig. 14, top) (discussed in Ref. 72)) to be discussed later. 

The effect of CPH-treatment upon the Na -depen-dent transport of the amino acid L-alanine was investigated [75]. The results of these studies showed that Na+-dependent transport of L-alanine was also reduced by the treatment with CPH and the overshoot phenomenon completely eliminated (Figure 7). In con-... 

As the mathematical representation of the complete overshoot curve is very complicated, only the amplitude of the peak is usually taken as an indicator of secondary active transport, provided that other causes of an overshoot phenomenon, such as osmotic swelling or temporary changes in membrane potential, can be excluded. 

There is, as yet, no complete theory to explain the phenomenon of polarographic maxima which is manifested by the observed current overshooting the limiting current. The causes are convective mass transport in the solution and adsorption. Three types of maximum have been identified [61] ... 

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