Potassium channels heterogeneous

Kelly JS, Larkman P, Penington NJ, Rainnie DG, McAllister-Williams H, Hodgkiss J. Serotonin receptor heterogeneity and the role of potassium channels in neuronal excitability. Adv Exp Med Biol 1991 287 177-191. 

The potassium channels are highly heterogeneous. The K channels gene only encodes a single repeat and four polypeptides come together to form the channel. Four types can be distinguished (1) the voltage-dependent K channels (2) the Ca" -activated channels (3) the receptor-coupled K" " channels, and other K channels (ATP-sensitive K" " channels, Na -activated K" " channels, etc.). 

Due to the presence of low-temperature desorption peak a new desorption site was included to phenomenological model of TPD experiments previously used for the description of the Cu-Na-FER samples [5], The fit of experimental TPD curves was performed in order to obtain adsorption energies and populations for individual site types sites denoted A (A1 pair), B (sites in P channel (A1 at T1 or T2)), C (sites in the M channel and intersection (A1 at T3 or T4)) [3] and D (newly introduced site). The new four-site model was able to reproduce experimental TPD curves (Figure 1). The desorption energy of site D is cu. 82 kJ.mol"1. This value is rather close to desorption energy of 84 kJ.mol"1 found for the site B , however, the desorption entropy obtained for sites B and D are rather different -70 J.K. mol 1 and -130 J.K. mol"1 for sites B and D , respectively. We propose that the desorption site D can be attributed to so-called heterogeneous dual-cation site, where the CO molecule is bonded between monovalent copper ion and potassium cation. The sum of the calculated populations of sites B and D (Figure 2) fits well previously published population of B site for the Cu-Na-FER zeolite [3], Because the population of C type sites was... 

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