Polyamines and pectins. I. Ion exchange and selectivity

The ion binding and exchange properties of putrescine, spermidine and spermine on purified walls of carrot cell suspensions were investigated by performing ion exchange isotherms, and compared to the behavior of Na+, Mg2+ and Ca2+. The cation exchange capacity of the carrot cell walls was 0.8 equivalent kg-1 dry matter and the ionic selectivity sequence of the walls for polyamines followed the sequence: spermine4+ > spermidine3+  calcium2+ > putrescine2+. The polyamines were only subjected to electroselectivity and probably did not induce any favorable supramolecular conformation of pectin like the one induced by calcium. Triangular ion exchanges were also performed with three diamines: ethane diamine, butanediamine and octanediamine. The shorter was the diamine, the higher the total adsorption and the selectivity of the exchange. The lower selectivity of the cell wall for putrescine was partly attributed to its inability to access and displace calcium from higher affinity sites within dimerized pectic sequences. The polyamine adsorption and exchange on pectic sequences could result in pectic signal modulation in pathogenesis as well as in differentiation.