Department of Radiation Oncology, The Cancer Institute of New Jersey and UMDNJ-Robert Wood Johnson Medical School, 195 Little Albany St, New Brunswick, NJ 08903, USA.
J Theor Biol. 2010 May 21;264(2):356-9. doi: 10.1016/j.jtbi.2010.02.024. Epub 2010 Feb 18.
Macromolecules occupy between 34% and 44% of the cell cytoplasm, about half the maximum packing density of spheres in three dimension. Yet, there is no clear understanding of what is special about this value. To address this fundamental question we investigate the effect of macromolecular crowding on cell metabolism. We develop a cell scale flux balance model capturing the main features of cell metabolism at different nutrient uptakes and macromolecular densities. Using this model we show there are two metabolic regimes at low and high nutrient uptakes. The latter regime is characterized by an optimal cytoplasmatic density where the increase of reaction rates by confinement and the decrease by diffusion slow-down balance. More important, the predicted optimal density is in the range of the experimentally determined density of Escherichia coli.
大分子占据细胞细胞质的 34%到 44%，约为三维空间中球体最大堆积密度的一半。然而，对于这个数值有什么特别之处还没有明确的认识。为了解决这个基本问题，我们研究了大分子拥挤对细胞代谢的影响。我们开发了一个细胞尺度的通量平衡模型，捕获了不同营养摄取和大分子密度下细胞代谢的主要特征。利用这个模型，我们表明在低营养摄取和高营养摄取时有两种代谢状态。后一种状态的特点是细胞质密度最佳，其中由于限制而增加的反应速率和由于扩散减速而降低的反应速率达到平衡。更重要的是，预测的最佳密度在实验确定的大肠杆菌密度范围内。
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