(1) The phenyl group is a monovalent organic radical, derived from benzene.(2) Fully deprotonating both acidic residues would appear to totally alter the selectivity of the channel, making it more suitable for divalent ions than monovalent ones.(3) These channels appear to be plasma membrane-located and non-selective, being permeable to both monovalent and divalent cations.(4) The hydrophobic fourfold channels, in contrast, present large energy barriers for both monovalent and divalent ions, practically insurmountable for the latter.(5) Thus, the competition between monovalent and divalent cations acts only on the DNA sites and does not act on the mica sites.
