Entropic and electrostatic effects on the folding free energy of a surface-attached biomolecule: an experimental and theoretical study.
Entropic and electrostatic effects on the folding free energy of a surface-attached biomolecule: an experimental and theoretical study.
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DOI：
10.1021/ja208436p
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发表时间：
2012-02-01
影响因子：
15
通讯作者：
Plaxco, Kevin W.
中科院分区：
文献类型：
--
作者：
Watkins, Herschel M.;Vallee-Belisle, Alexis;Ricci, Francesco;Makarov, Dmitrii E.;Plaxco, Kevin W.
表面束缚生物分子在许多生物过程和生物技术中发挥着关键作用。然而，虽然这种表面附着的物理后果已经得到了重要的理论研究，但迄今为止，这个问题的实验研究相对较少。作为回应，我们在此提出了一项定量实验和理论研究，研究附着在带电（但显然是惰性的）表面上会在多大程度上改变简单生物分子的折叠自由能。具体来说，我们测量了 DNA 茎环在溶液中以及当位点特异性附着在带负电的羟基烷烃涂覆的金表面上时的折叠自由能。我们发现，虽然表面附着在低离子强度下不稳定，但在离子强度高于约 130 mM 时变得稳定。这种行为大概反映了两种相互竞争的机制：排除体积效应，通过减少未折叠状态的熵来稳定折叠构象，以及静电，在较低的离子强度下，通过带负电表面的排斥力使更紧凑的折叠状态不稳定。为了检验这一假设，我们采用了现有的表面结合聚电解质静电理论和表面结合聚合物熵理论来模拟这两种效应。尽管缺乏任何拟合参数，这些理论模型定量地符合我们的实验结果，这表明，对于该系统，当前对表面静电和排除体积效应的了解是相当完整和准确的。
Surface-tethered biomolecules play key roles in many biological processes and biotechnologies. However, while the physical consequences of such surface attachment have seen significant theoretical study, to date this issue has seen relatively little experimental investigation. In response we present here a quantitative experimental and theoretical study of the extent to which attachment to a charged –but otherwise apparently inert– surface alters the folding free energy of a simple biomolecule. Specifically, we have measured the folding free energy of a DNA stem loop both in solution and when site-specifically attached to a negatively charged, hydroxyl-alkane-coated gold surface. We find that, whereas surface attachment is destabilizing at low ionic strength it becomes stabilizing at ionic strengths above ~130 mM. This behavior presumably reflects two competing mechanisms: excluded volume effects, which stabilize the folded conformation by reducing the entropy of the unfolded state, and electrostatics, which, at lower ionic strengths, destabilizes the more compact folded state via repulsion from the negatively charged surface. To test this hypothesis we have employed existing theories of the electrostatics of surface-bound polyelectrolytes and the entropy of surface-bound polymers to model both effects. Despite lacking any fitted parameters, these theoretical models quantitatively fit our experimental results, suggesting that, for this system, current knowledge of both surface electrostatics and excluded volume effects is reasonably complete and accurate.
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影响因子：
15
作者：
Kaiser, Wolfgang;Rant, Ulrich
通讯作者：
Rant, Ulrich
影响因子：
3.9
作者：
Huang, E;Zhou, FM;Deng, L
通讯作者：
Deng, L
DOI：
10.1073/pnas.0601210103
发表时间：
2006-05-30
影响因子：
11.1
作者：
Friedel, Miriam;Baumketner, Andrij;Shea, Joan-Emma
通讯作者：
Shea, Joan-Emma
影响因子：
5.4
作者：
Baouendi, Meriem;Cognet, Jean A. H.;du Penhoat, Catherine Herve
通讯作者：
du Penhoat, Catherine Herve
影响因子：
1.7
作者：
Chen, Ying-Cai;Luo, Meng-Bo
通讯作者：
Luo, Meng-Bo