Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
J Chem Phys. 2011 Mar 7;134(9):095104. doi: 10.1063/1.3556671.
The dependence of the melting temperature increase (ΔT(m)) of the protein ubiquitin on the volume fraction (ϕ) of several commonly used macromolecular crowding agents (dextran 6, 40, and 70 and ficoll 70) was quantitatively examined and compared to a recently developed theoretical crowding model, i.e., ΔT(m) ∼ (R(g)∕R(c))(α)φ(α∕3). We found that in the current case this model correctly predicts the power-law dependence of ΔT(m) on φ but significantly overestimates the role of the size (i.e., R(c)) of the crowding agent. In addition, we found that for ubiquitin the exponent α is in the range of 4.1-6.5, suggesting that the relation of α=3∕(3ν-1) is a better choice for estimating α based on the Flory coefficient (ν) of the polypeptide chain. Taken together these findings highlight the importance of improving our knowledge and theoretical treatment of the microcompartmentalization of the commonly used model crowding agents.
我们定量考察了几种常用的高分子拥挤试剂（葡聚糖 6、40 和 70 以及菲可 70）对蛋白质泛素的熔点升高（ΔT(m)）的依赖关系，并与最近提出的理论拥挤模型进行了比较，即 ΔT(m)∼(R(g)∕R(c))(α)φ(α∕3)。我们发现，在当前情况下，该模型正确地预测了 ΔT(m)对 φ 的幂律依赖性，但严重高估了拥挤试剂尺寸（即 R(c)）的作用。此外，我们发现对于泛素，指数 α 的范围在 4.1-6.5 之间，这表明对于基于多肽链的弗洛里系数（ν）来估计 α，α=3∕(3ν-1)的关系是一个更好的选择。总的来说，这些发现强调了提高我们对常用模型拥挤试剂的微分隔的认识和理论处理的重要性。
