Peptide Desorption Kinetics from Single Molecule Force Spectroscopy Studies
Peptide Desorption Kinetics from Single Molecule Force Spectroscopy Studies
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DOI：
10.1021/ja410278r
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发表时间：
2014-01-15
影响因子：
15
通讯作者：
Hugel, Thorsten
中科院分区：
文献类型：
--
作者：
Krysiak, Stefanie;Liese, Susanne;Hugel, Thorsten
我们使用实验/理论相结合的方法来确定聚酪氨酸和聚赖氨酸同肽从平坦表面的固有单体解吸速率 k(0)。为此，在两个互补的实验方案中，将单个多肽分子共价连接到 AFM 悬臂尖端，并从疏水性自组装单层中解吸。在恒定拉速方案中，悬臂以有限速度远离表面，并记录恒定平台力状态结束和聚合物分离的距离。在等待时间协议中，悬臂保持在表面上方固定距离处，并记录聚合物分离的时间。通过添加乙醇或盐系统地改变水性溶剂的质量，解吸平台力在 10 至 90 pN 之间变化。将两个协议的实验数据与简单的双态动力学聚合物理论同时拟合，可以明确地解开并确定与聚合物轮廓长度 L、库恩长度 a、吸附自由能 lambda 和固有单体解吸速率 k(0) 相对应的模型参数。对我们的分析至关重要的是，统计上显着数量的单聚合物解吸实验是使用同一种单聚合物分子针对不同的溶剂质量进行的。大约 k(0) 接近 10(5) Hz 的惊人低值表明单一聚合物解吸过程中具有显着的协同性。
We use a combined experimental/theoretical approach to determine the intrinsic monomeric desorption rate k(0), of polytyrosine and polylysine homopeptides from flat surfaces. To this end, single polypeptide molecules are covalently attached to an AFM cantilever tip and desorbed from hydrophobic self-assembled monolayers in two complementary experimental protocols. In the constant-pulling-velocity protocol, the cantilever is moved at finite velocity away from the surface and the distance at which the constant plateau force regime ends and the polymer detaches is recorded. In the waiting-time protocol, the cantilever is held at a fixed distance above the surface and the time until the polymer detaches is recorded. The desorption plateau force is varied between 10 and 90 pN, by systematically changing the aqueous solvent quality via the addition of ethanol or salt. A simultaneous fit of the experimental data from both protocols with simple two-state kinetic polymer theory allows to unambiguously disentangle and determine the model parameters corresponding to polymer contour length L, Kuhn length a, adsorption free energy lambda, and intrinsic monomeric desorption rate k(0). Crucial to our analysis is that a statistically significant number of single-polymer desorption experiments are done with one and the same single polymer molecule for different solvent qualities. The surprisingly low value of about k(0) approximate to 10(5) Hz points to significant cooperativity in the desorption process of single polymers.