Science, Vol 199, Issue 4332, 994-996
Copyright © 1978 by American Association for the Advancement of Science
Cyclic polyether-protonated organic amine binding: significance in enzymatic and ion transport processes
RM Izatt,
NE Izatt,
BE Rossiter,
JJ Christensen,
and
BL Haymore
The cyclic polyether, 18-crown-6, reacts with protonated amines in methanol to form complexes whose formation constants (log K) decrease in the order NH4+, RNH3+ greater than R2NH2+ greater than R3NH+. In the case of the organic amines, this stability order is identical to the earlier observed permeability sequence for protonated organic amines in glyceryl dioleate bilayers treated with valinomycin, nonactin, or gramicidin, and in bullfrog and rabbit gallbladder membranes. The decrease in log K values in the above series is primarily a result of decreased enthalpy change (deltaH) values, the entropy change (TdeltaS) term being essentially constant for the systems studied.
