It is now interesting to compare the effective rate constants of the spontaneous incorporation of EB with both ions. Accordingly, for Na + a kspon value of 2•10 -7 min -1 is obtained which is smaller by 4 orders of magnitude then the one determined for K + of 2.5•10 -3 min -1 . For the sake of comparison: if one assumes similar molecular mechanisms (and all other parameters being equal), this difference of the rate constants would translate to a drastically higher effective activation barrier of EB incorporation in presence of Na + ions by ca. 23.5 kJ/mol according to