To elucidate how an ion channel operates it is necessary to be able to record how the channel opens and closes. This appeared elusive since the ionic current through a single ion channel is extraordinarily small. In addition, the small ion channel molecules are embedded in the cell membrane. Neher and Sakmann succeeded in solving these difficulties. When a single ion channel opens, ions will move through the channel as an electric current, since they are charged.
Ion channels are of different types.
Some only permit the flow of positively charged sodium, potassium or calcium ions, others only negatively charged chloride ions. Neher and Sakmann discovered how this specificity is accomplished. One reason is the diameter of the ion channel, which is adapted to the diameter of a particular ion. In one class of ion channels, there are also two rings of positively or negatively charged amino acids. Neher and Sakmann's scientific achievements have radically changed our views on the function of the cell and the contents of text books of cell biology.