Reagents Specific for Cell Surface Components

Mercury, diazonium ions and dyes which bind nucleic acids were covalently linked to dextrans using methods that resulted in non‐hydrolyzable reagent‐dextran bonds without impairing the binding abilities of the reagents, i.e. these dextran derivatives reacted with thiols, phenols/imidazoles and nucleic acids respectively. Since these dextran derivatives cannot penetrate into cells and since dextran itself does not bind to cells, these compounds represent reagents specific for the cell surface. They may be used both to evaluate cell surface constituents of intact cells and to affect viable cells via an interaction with those constituents. Mercury‐dextran was found to bind to cells; the amount of mercury thus attached to the cells was about ten times smaller than when an equivalent concentration of free mercury ions was used. Mercury‐dextran, bound to cells after a 30‐min exposure at room temperature, was localized on the surface of these cells, as sodium borohydride reduced this complex giving rise to the intact cells, elementary mercury and free dextran which was released into medium. When cells were constantly exposed to the mercury‐dextran, its toxic effects were comparable to that of free mercury ions. Diazonium‐dextran, which also binds tightly to the cell surface, was also considerably toxic. Dextrans substituted with dyes which bind to nucleic acids were less toxic than the parent dyes themselves; it was shown that the attachment of such a dye to dextran decreased the binding of dye to cells under detection limits.