Single centrosome manipulation reveals its electric charge and associated dynamic structure.
The centrosome is the major microtubule-organizing center in animal cells and consists of a pair of centrioles surrounded by a pericentriolar material. We demonstrate laser manipulation of individual early Drosophila embryo centrosomes in between two microelectrodes to reveal that it is a net negatively charged organelle with a very low isoelectric region (3.1 +/- 0.1). From this single-organelle electrophoresis, we infer an effective charge smaller than or on the order of 10(3) electrons, which corresponds to a surface-charge density significantly smaller than that of microtubules. We show, however, that the charge of the centrosome has a remarkable influence over its own structure. Specifically, we investigate the hydrodynamic behavior of the centrosome by measuring its size by both Stokes law and thermal-fluctuation spectral analysis of force. We find, on the one hand, that the hydrodynamic size of the centrosome is 60% larger than its electron microscopy diameter, and on the other hand, that this physiological expansion is produced by the electric field that drains to the centrosome, a self-effect that modulates its structural behavior via environmental pH. This methodology further proves useful for studying the action of different environmental conditions, such as the presence of Ca(2+), over the thermally induced dynamic structure of the centrosome.
Hormeño
S
S
Department of Macromolecular Structure, Centro Nacional de Biotecnología, CSIC, Madrid, Spain.
Ibarra
B
B
Chichón
F J
FJ
Habermann
K
K
Lange
B M H
BM
Valpuesta
J M
JM
Carrascosa
J L
JL
Arias-Gonzalez
J R
JR
D000818:Animals; D018385:Centrosome / Q000737:chemistry* / Q000502:physiology*; D003198:Computer Simulation; D004331:Drosophila melanogaster; D004574:Electromagnetic Fields; D004586:Electrophoresis / Q000379:methods*; D008846:Micromanipulation / Q000379:methods*; D008954:Models, Biological; D055672:Static Electricity
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