Single channel properties of D-Leu2-gramicidin A. Side chain modulation of channel lifetime

The channel forming properties of synthetic gramicidin A and DLeu2-gramicidin A were compared in black lipid membranes. The most probable single channel conductance was identical for both derivatives but in each case a distribution of smaller channel sizes was observed. However, the lifetime of the channel formed by DLeu2-gramicidin A was considerably shorter than for gramicidin A. The DLeu2 substitution is considered to interfere with the head to head hydrogen bonding which forms the conducting dimer, thus destabilizing the dimeric structure of the channel and reducing the lifetime. This represents the first demonstration of side-chain modulation of channel lifetime.