Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, Utah.
Biophys J. 2024 Aug 20;123(16):2638-2640. doi: 10.1016/j.bpj.2024.05.034. Epub 2024 Jun 18.
In a recent study, Garner et al. investigated diffusion in the cytoplasm of fission yeasts, revealing vast heterogeneity in intracellular viscosity. Their conclusion was based on a combination of single-particle-tracking experiments and Brownian dynamics simulations. However, in their simulations, the diffusivity gradient term has been neglected-an assumption common in some biophysical applications but unjustified in this particular case due to spatial variations in diffusivity. Here, we aim to comment on the importance of the diffusivity gradient term and the physical consequences of not including it. We also demonstrate that omitting this term likely leads to overestimating fission yeast intracellular viscosity variance and underestimating its mean. Additionally, we propose modifications to the simulations to incorporate the gradient term.
在最近的一项研究中，Garner 等人研究了裂变酵母细胞质中的扩散，揭示了细胞内粘度的巨大异质性。他们的结论是基于单个粒子跟踪实验和布朗动力学模拟的结合。然而，在他们的模拟中，忽略了扩散率梯度项——这一假设在一些生物物理应用中很常见，但在这种特殊情况下由于扩散率的空间变化是不合理的。在这里，我们旨在评论扩散率梯度项的重要性以及不包括它的物理后果。我们还证明，忽略这个项可能会导致高估裂变酵母细胞内粘度的方差，并低估其平均值。此外，我们还提出了对模拟的修改，以纳入梯度项。
