title: High-yield synthesis of a [3H]ethylenediamine ditetrodotoxin derivative.
abstract: [3H]Tetrodotoxin [( 3H]TTX) and a [3H]ethylenediamine derivative of TTX are the most widely used ligands for the study of the Na channel. The former ligand presents a low specific radioactivity (1 Ci/mmol) while the latter is highly labeled (30 Ci/mmol). However, its two-step synthesis, i.e., mild oxidation followed by coupling of [3H]ethylenediamine, has been described with a low overall yield of 1.7%. In this work, more favorable experimental conditions are defined for the limiting reaction, i.e., the oxidation step, using [14C]testosterone as a model molecule. Applied to the oxidation of tetrodotoxin, this procedure produces yield values of 30-50%, as determined by high-performance liquid chromatography. Moreover, two oxidized TTX molecules appear to be covalently linked to [3H]ethylenediamine, yielding a new labeled tetrodotoxin derivative with a specific radioactivity of 45 Ci/mmol and a dissociation constant of 0.6 nM for electroplax membranes.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D004593:Electrophorus; D007473:Ion Channels / Q000378:metabolism; D007553:Isotope Labeling; D051379:Mice; D010084:Oxidation-Reduction; D012588:Scintillation Counting; D012964:Sodium / Q000378:metabolism; D013739:Testosterone; D013779:Tetrodotoxin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D007473:Ion Channels; D013739:Testosterone; D013779:Tetrodotoxin; C041954:N,N'-ethylenediamineditetrodotoxin; D012964:Sodium