Partitioning of individual flexible polymers into a nanoscopic protein pore
Partitioning of individual flexible polymers into a nanoscopic protein pore
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DOI：
10.1016/s0006-3495(03)74529-9
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发表时间：
2003-08-01
影响因子：
3.4
通讯作者：
Bayley, H
中科院分区：
文献类型：
--
作者：
Movileanu, L;Cheley, S;Bayley, H
聚合物动力学在材料科学、生物技术和医学中具有根本的重要性。然而，很少有人知道的动力学的灵活的聚合物分子到纳米尺寸的孔的分区。我们采用电记录来探测单个聚（乙二醇）（PEG）分子的分区，在稀释制度附近的浓度，进入由葡萄球菌α-溶血素（alphaHL）形成的单个蛋白质孔的跨膜β-桶。α-溶血素孔与PEG（M-w 940-6000 Da）的相互作用分为两类：短持续时间事件（τ类似于20 μ s），占总数的85%;长持续时间事件（τ类似于100 ms），占总数的15%。这两类事件的关联速率常数（k（on））强烈依赖于聚合物质量，和值的k（on）的范围超过两个数量级。相比之下，解离速率常数（k（off））表现出对质量的弱依赖性，这表明聚合物链在进入孔之前在很大程度上被压实，并且在它们离开之前不会分解到显著的程度。使用k（on）和k（off）的值来确定PEG在本体水相和孔腔之间的分配系数（Pi）。Pi的低值与PEG链和孔的内表面之间的可忽略的相互作用一致，这与离子强度无关。对于长事件，根据Daoud和de Gennes的标度律，Pi的值随聚合物质量呈指数下降。对于大于类似tokDa的PEG分子，Pi达到极限值，表明这些PEG链不能完全装入β桶。
Polymer dynamics are of fundamental importance in materials science, biotechnology, and medicine. However, very little is known about the kinetics of partitioning of flexible polymer molecules into pores of nanometer dimensions. We employed electrical recording to probe the partitioning of single poly(ethylene glycol) (PEG) molecules, at concentrations near the dilute regime, into the transmembrane beta-barrel of individual protein pores formed from staphylococcal alpha-hemolysin (alphaHL). The interactions of the alpha-hemolysin pore with the PEGs (M-w 940-6000 Da) fell into two classes: short-duration events (tausimilar to20 mus), similar to85% of the total, and long-duration events (tausimilar to100 ms),; 15% of the total. The association rate constants (k(on)) for both classes of events were strongly dependent on polymer mass, and values of k(on) ranged over two orders of magnitude. By contrast, the dissociation rate constants (k(off)) exhibited a weak dependence on mass, suggesting that the polymer chains are largely compacted before they enter the pore, and do not decompact to a significant extent before they exit. The values of k(on) and k(off) were used to determine partition coeffients (Pi) for the PEGs between the bulk aqueous phase and the pore lumen. The low values of Pi are in keeping with a negligible interaction between the PEG chains and the interior surface of the pore, which is independent of ionic strength. For the long events, values of Pi decrease exponentially with polymer mass, according to the scaling law of Daoud and de Gennes. For PEG molecules larger than similar tokDa, Pi reached a limiting value suggesting that these PEG chains cannot fit entirely into the beta-barrel.