Related Experiment Video
Updated: Oct 9, 2026

Electrophysiological Methods for Measuring Photopigment Levels in Drosophila Photoreceptors
Published on: June 2, 2022
The electric charge of pigment granules in pigment cells
M F Testorf1, I Lundström, P A Oberg
1Department of Biomedical Engineering, University Hospital, Linköping University, Sweden. marte@imt.liu.se
Abstract:
Black pigment cells called melanophores change colour in response to environmental changes and have lately been studied as promising biosensors. To further elucidate the intracellular processes involved in the colour changes of these cells, and to find optimal biosensing principles, the electric charge of intracellular pigment granules, melanosomes, has been determined in vitro by electrophoresis. Melanosomes from the two extreme states in the cell colour change (aggregated and dispersed melanosomes) were measured. The charge was found to be -1.5 x 10(-16) and -1.7 x 10(-16) C, aggregated and dispersed melanosomes, respectively, without significant difference between the two conditions. This charge is of the same order of magnitude as the one of 1000 electrons. The origin of the melanosome charge, and the use of these findings in new biosensor principles, is discussed.
Related Concept Videos
What is an Electrochemical Gradient?
Electrochemical Gradient and Channel Proteins: An Overview
The electrical gradient: The electrical gradient across cell membranes refers to the difference in electric charge between the inside and outside of a cell. This difference drives the movement of ions towards or away from the cells. For instance, if the inside of the cell is more negatively charged relative to the...
G-Protein Gated Ion Channels
Sensory organs,...
Electromotive Force
Generation of Action Potential in Skeletal Muscles
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Electric Charges
The English physicist William Gilbert studied the phenomenon of static electricity in...

