The electric charge of pigment granules in pigment cells

Black pigment cells called melanophores change colour in response to enviro nmental changes and have lately been studied as promising biosensors. To fu rther elucidate the intracellular processes involved in the colour changes of these cells, and to find optimal biosensing principles, the electric cha rge of intracellular pigment granules, melanosomes, has been determined in vitro by electrophoresis. Melanosomes from the two extreme states in the ce ll colour change (aggregated and dispersed melanosomes) were measured. The charge was found to be -1.5.10(-16) and -1.7.10(-16) C, aggregated and disp ersed melanosomes, respectively, without significant difference between the two conditions. This charge is of the same order of magnitude as the one o f 1000 electrons. The origin of the melanosome charge, and the use of these findings in new biosensor principles. is discussed. (C) 2001 Elsevier Scie nce B.V. All rights reserved.