Effective patchiness from critical points of a coarse-grained protein model with explicit shape and charge anisotropy

IF 2.9 3区 化学 Q3 CHEMISTRY, PHYSICAL Soft Matter Pub Date : 2024-10-08 DOI:10.1039/D4SM00867G
Jens Weimar, Frank Hirschmann and Martin Oettel
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Abstract

Colloidal model systems are successful in rationalizing emergent phenomena like aggregation, rheology and phase behaviour of protein solutions. Colloidal theory in conjunction with isotropic interaction models is often employed to estimate the stability of such solutions. In particular, a universal criterion for the reduced second virial coefficient at the critical point is frequently invoked which is based on the behavior of short-range attractive fluids (Noro–Frenkel rule, ). However, if anisotropic models for the protein–protein interaction are considered, e.g. the Kern–Frenkel (KF) patchy particle model, the value of the criterion is shifted to lower values and explicitly depends on the number of patches. If an explicit shape anisotropy is considered, as e.g. in a coarse-grained protein model, the normalization of becomes ambiguous to some extent, as no unique exclusion volume can be defined anymore. Here, we investigate a low-resolution, coarse-grained model for the globular protein bovine serum albumin (BSA) and study effects of charge-anisotropy on the phase diagram (determined by simulations) at the isoelectric point. We present methods of assigning an “effective patchiness” to our protein model by comparing its critical properties to the KF model. We find that doubling the native charges increases the critical temperature Tc by ≈14% and that our BSA model can be compared to a 3 to 5 patch KF model. Finally, we argue that applying existing criteria from colloidal theory should be done with care, due to multiple, physically plausible ways of how to assign effective diameters to shape-anisotropic models.

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具有明确形状和电荷各向异性的粗粒度蛋白质模型临界点的有效斑块度。
胶体模型系统可以成功地合理解释蛋白质溶液的聚集、流变和相行为等新出现的现象。胶体理论与各向同性相互作用模型相结合,经常被用来估算此类溶液的稳定性。特别是,临界点的第二维里系数降低的通用标准经常被引用,该标准基于短程吸引力流体的行为(Noro-Frenkel 规则)。然而,如果考虑到蛋白质-蛋白质相互作用的各向异性模型,例如 Kern-Frenkel (KF) 补丁粒子模型,则该标准的值会降低,并明确取决于补丁的数量。如果考虑到明确的形状各向异性,例如在粗粒度蛋白质模型中,由于无法再定义唯一的排除体积,因此归一化标准在某种程度上变得模糊不清。在此,我们研究了球状蛋白质牛血清白蛋白(BSA)的低分辨率粗粒度模型,并研究了电荷各向异性对等电点相图(通过模拟确定)的影响。通过比较蛋白质模型与 KF 模型的临界特性,我们提出了为蛋白质模型分配 "有效斑块度 "的方法。我们发现,原生电荷增加一倍会使临界温度 Tc 上升≈14%,而且我们的 BSA 模型可与 3 至 5 补丁的 KF 模型进行比较。最后,我们认为在应用胶体理论的现有标准时应小心谨慎,因为有多种物理上合理的方法可以为形状各向异性模型分配有效直径。
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来源期刊
Soft Matter
Soft Matter 工程技术-材料科学:综合
CiteScore
6.00
自引率
5.90%
发文量
891
审稿时长
1.9 months
期刊介绍: Where physics meets chemistry meets biology for fundamental soft matter research.
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