Discovery of "punch-through" or membrane electrical breakdown and electroporation.

As part of a detailed study in Alex Hope's laboratory of the V-I characteristics of the membrane of the giant cells of Chara corallina, it was discovered that at a well defined potential difference of around 500 mV (depending on the temperature), the cell membrane undergoes a reversible electrical breakdown. The author coined the word "punchthrough" to describe this electrical breakdown phenomenon. Detailed studies followed on the nature of this electrical breakdown phenomenon, in various cells, aimed at elucidating the physical mechanism(s) involved. The applications and the significance of the phenomenon that were subsequently developed in later years were not foreseen at that time. Electrical breakdown/electroporation is now a commonplace procedure and has entered into the mainstream biological vocabulary. Here we trace its humble beginnings to experiments carried out in Alex Hope's laboratory and review briefly some of the aspects of this phenomenon and its applications that were developed much later by others as well as the author. The discovery of membrane electrical breakdown described below took whilst the author was his student of Alex Hope but whilst Alex was away on sabbatical leave in the UK. Because this occurred in his absence, Alex Hope elected to not put his name on the paper that described the discovery in 1965.