Interaction of the 2,6-dimethoxysemiquinone and ascorbyl free radicals with Ehrlich ascites cells: a probe of cell-surface charge.
The rate of quenching by Ehrlich ascites cells of anionic 2,6-dimethoxy-p-semiquinone and ascorbyl free radicals is investigated as a function of cell concentration, the blocking of cell-surface sulfhydryl groups by N-ethylmaleimide, and the reduction of cell-surface charge by neuraminidase. The rate of quenching is found to be proportional to cell viability and to the number of free cell-surface sulfhydryl groups. The enzymatic action of neuraminidase results in an increase of the free radical quenching rate, indicating that this rate can be used as a probe of cell-surface charge. Measurements as a function of the ionic strength of the suspending electrolyte gave a value of -1.22 microC X cm-2 for the charge density at the ascites cell surface. This is equivalent to a surface membrane potential of -14 mV for a 150 mM NaCl electrolyte and is a value in good agreement with published electrophoresis data.
D000818:Animals; D001205:Ascorbic Acid; D016227:Benzoquinones; D002286:Carcinoma, Ehrlich Tumor / Q000503:physiopathology*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D004553:Electric Conductivity; D005033:Ethylmaleimide / Q000494:pharmacology; D005609:Free Radicals; D007700:Kinetics; D051379:Mice; D011809:Quinones; D013499:Surface Properties; D013816:Thermodynamics
D016227:Benzoquinones; D005609:Free Radicals; D011809:Quinones; C041134:2,6-dimethoxysemiquinone radicals; D005033:Ethylmaleimide; D001205:Ascorbic Acid