TY - JOUR
T1 - Hindered diffusion of inert tracer particles in the cytoplasm of mouse 3T3 cells.
AU - Luby-Phelps, K.
AU - Castle, P. E.
AU - Taylor, D. L.
AU - Lanni, F.
PY - 1987/7
Y1 - 1987/7
N2 - Using fluorescence recovery after photobleaching, we have studied the diffusion of fluorescein-labeled, size-fractionated Ficoll in the cytoplasmic space of living Swiss 3T3 cells as a probe of the physical chemical properties of cytoplasm. The results reported here corroborate and extend the results of earlier experiments with fluorescein-labeled, size-fractionated dextran: diffusion of nonbinding particles in cytoplasm is hindered in a size-dependent manner. Extrapolation of the data suggests that particles larger than 260 A in radius may be completely nondiffusible in the cytoplasmic space. In contrast, diffusion of Ficoll in protein solutions of concentration comparable to the range reported for cytoplasm is not hindered in a size-dependent manner. Although we cannot at present distinguish among several physical chemical models for the organization of cytoplasm, these results make it clear that cytoplasm possesses some sort of higher-order intermolecular interactions (structure) not found in simple aqueous protein solutions, even at high concentration. These results also suggest that, for native cytoplasmic particles whose smallest radial dimension approaches 260 A, size may be as important a determinant of cytoplasmic diffusibility as binding specificity. This would include most endosomes, polyribosomes, and the larger multienzyme complexes.
AB - Using fluorescence recovery after photobleaching, we have studied the diffusion of fluorescein-labeled, size-fractionated Ficoll in the cytoplasmic space of living Swiss 3T3 cells as a probe of the physical chemical properties of cytoplasm. The results reported here corroborate and extend the results of earlier experiments with fluorescein-labeled, size-fractionated dextran: diffusion of nonbinding particles in cytoplasm is hindered in a size-dependent manner. Extrapolation of the data suggests that particles larger than 260 A in radius may be completely nondiffusible in the cytoplasmic space. In contrast, diffusion of Ficoll in protein solutions of concentration comparable to the range reported for cytoplasm is not hindered in a size-dependent manner. Although we cannot at present distinguish among several physical chemical models for the organization of cytoplasm, these results make it clear that cytoplasm possesses some sort of higher-order intermolecular interactions (structure) not found in simple aqueous protein solutions, even at high concentration. These results also suggest that, for native cytoplasmic particles whose smallest radial dimension approaches 260 A, size may be as important a determinant of cytoplasmic diffusibility as binding specificity. This would include most endosomes, polyribosomes, and the larger multienzyme complexes.
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U2 - 10.1073/pnas.84.14.4910
DO - 10.1073/pnas.84.14.4910
M3 - Article
C2 - 3474634
AN - SCOPUS:0023375957
SN - 0027-8424
VL - 84
SP - 4910
EP - 4913
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 14
ER -