HINDERED DIFFUSION OF INERT TRACER PARTICLES IN THE CYTOPLASM OF MOUSE 3T3 CELLS
HINDERED DIFFUSION OF INERT TRACER PARTICLES IN THE CYTOPLASM OF MOUSE 3T3 CELLS
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DOI：
10.1073/pnas.84.14.4910
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发表时间：
1987-07-01
影响因子：
11.1
通讯作者：
LANNI, F
中科院分区：
文献类型：
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作者：
LUBYPHELPS, K;CASTLE, PE;LANNI, F
利用光漂白后的荧光恢复，我们研究了荧光素标记的、尺寸分级的聚蔗糖在活体 Swiss 3T3 细胞的细胞质空间中的扩散，作为细胞质物理化学性质的探针。这里报告的结果证实并扩展了早期使用荧光素标记的尺寸分级葡聚糖进行的实验的结果：细胞质中非结合颗粒的扩散以尺寸依赖性方式受到阻碍。数据外推表明大于 260 ANG 的颗粒。半径内的粒子在细胞质空间中可能完全不可扩散。相反，Ficoll 在浓度与报告的细胞质范围相当的蛋白质溶液中的扩散不会以大小依赖性方式受到阻碍。尽管我们目前无法区分细胞质组织的几种物理化学模型，但这些结果清楚地表明，细胞质具有某种高级分子间相互作用（结构），而这种相互作用在简单的水性蛋白质溶液中是不存在的，即使在高浓度下也是如此。这些结果还表明，对于最小径向尺寸接近260埃的天然细胞质颗粒来说，尺寸可能与结合特异性一样重要，是细胞质扩散性的决定因素。这将包括大多数内体、多聚核糖体和更大的多酶复合物。
Using fluorescence recovery after photobleaching, we have studied the diffusion of fluorescein-labeled, size-fractionated Ficoll in the cytoplsmic 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 .ANG. 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 solutinos, even at high concentration. These results also suggest that, for native cytoplasmic particles whose smallest radial dimension approaches 260 .ANG., size may be as important a determinant of cytoplasmic diffusibility as binding specificity. This would include most endosomes, polyribosomes, and the larger multienzyme complexes.