Protein target complex

A complex of a non-activated extracellularly applied first compound bound to a targeted first intracellular protein, wherein the non-activated extracellularly applied compound is substantially unable to cross an intact cell membrane;

• wherein the non-activated extracellularly applied compound selectively interacts directly with an at least one cell constituent, wherein the at least one cell constituent is the at least one first intracellular protein, and
• wherein the first intracellular protein is any one or more of 40-70 kDa intracellular proteins,
• the complex providing discrimination between live cells and cells whose plasma membrane has lost its integrity, and having a ratio of an amount of the non-activated extracellularly applied compound contained within a given quantity of cells whose plasma membrane has lost integrity by interacting directly with the at least one cell constituent divided by an amount of the non-activated extracellularly applied compound that is bound to a same given quantity of living cells ([amount dead cell] /[amount living cell]), wherein the ratio is larger than 10 and smaller than 1010.