Department of Chemical Engineering, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
Biomacromolecules. 2014 Feb 10;15(2):541-7. doi: 10.1021/bm401536v. Epub 2014 Jan 9.
We report the effect of physical properties, such as flexibility and polymer density, of nanogel particles (NPs) on the association/dissociation rates constant (kon and koff) and equilibrium constants (Kd) of multipoint protein recognition process. NPs having different flexibilities and densities at 25 °C were synthesized by tuning cross-linking degrees and the volume phase transition (VPT) temperature. Rate constants were quantified by analyzing time course of protein binding process on NPs monitored by a quartz crystal microbalance (QCM). Both kon and koff of swollen phase NPs increased with decreasing cross-linking degree, whereas cross-linking degree did not affect kon and koff of the collapsed phase NPs, indicating that polymer density of NPs governs kon and koff. The results also suggest that the mechanical flexibility of NPs, defined as the Young's modulus, does not always have crucial roles in the multipoint molecular recognition process. On the other hand, Kd was independent of the cross-linking degree and depended only on the phase of NPs, indicating that molecular-scale flexibility, such as side-chain and segmental-mode mobility, as well as the conformation change, of polymer chains assist the formation of stable binding sites in NPs. Our results reveal the rationale for designing NPs having desired affinity and binding kinetics to target molecules.
我们研究了纳米凝胶粒子（NPs）的物理性质，如柔韧性和聚合物密度，对多点蛋白质识别过程的结合/解离速率常数（kon 和 koff）和平衡常数（Kd）的影响。通过调节交联度和体积相转变（VPT）温度，在 25°C 下合成了具有不同柔韧性和密度的 NPs。通过分析石英晶体微天平（QCM）监测的 NPs 上蛋白质结合过程的时程，定量了速率常数。溶胀相 NPs 的 kon 和 koff 均随交联度的降低而增加，而坍塌相 NPs 的 kon 和 koff 不受交联度的影响，表明 NPs 的聚合物密度控制着 kon 和 koff。结果还表明，NPs 的力学柔韧性（定义为杨氏模量）并不总是在多点分子识别过程中起关键作用。另一方面，Kd 与交联度无关，仅取决于 NPs 的相，表明聚合物链的分子尺度柔韧性，如侧链和链段运动性以及构象变化，有助于在 NPs 中形成稳定的结合位点。我们的结果揭示了设计具有所需亲和力和结合动力学的 NPs 以靶向分子的原理。
