Studies on the chemical properties of the acetylcholine receptor site of the frog neuromuscular junction.

The effect of a water-soluble carbodiimide has been used to study the nature of the presumed anionic part of the acetylcholine (ACh) receptor at the frog neuromuscular junction. The ACh sensitivity has been measured by the moving fluid electrode method and by recording end plate potentials with microelectrodes. The carbodiimide blocked ACh sensitivity without marked effect on the membrane resistance or potential difference. The conditions of reversibility of the block and the results obtained with phospholipids suggest that a carboxyl group is important in the combination of ACh with the receptor.