We present a small-angle neutron scattering (SANS) and neutron spin echo investigation on the structure and dynamics of irreversible single-chain nanoparticles (SCNPs) in dilute solution. SCNPs are ultra-small soft nano-objects obtained by intramolecular folding/collapse of individual linear polymer chains (precursors). SANS has demonstrated the compaction of macromolecules upon creation of internal cross-links, although their conformation is far from a globular topology. To describe the dynamic structure factor of the SCNPs in solution, we have taken into account their dual polymer/nanoparticle character and applied theoretical approximations based on the Zimm model. The study reveals relaxation of internal degrees of freedom but clearly slowed down with respect to the precursor counterparts. This effect is attributed to the internal friction associated to the compartmentation in domains within the macromolecule. We discuss the structural and dynamical similarities of SCNPs with disordered proteins, in particular with intrinsically disordered proteins. The high internal friction in both cases seems to be associated to the existence of internal domains.

中文翻译：

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不可逆单链纳米粒子在稀溶液中的结构和动力学。中子散射研究

我们目前在稀溶液中不可逆单链纳米粒子（SCNPs）的结构和动力学的小角度中子散射（SANS）和中子自旋回波研究。SCNP是通过单个线性聚合物链（前体）的分子内折叠/折叠而获得的超小型软纳米物体。SANS已证明在创建内部交联时可压缩大分子，尽管其构型远非球形拓扑结构。为了描述溶液中SCNP的动态结构因素，我们考虑了它们的双重聚合物/纳米颗粒特征，并基于Zimm模型应用了理论近似值。这项研究揭示了内部自由度的放松，但相对于前者而言明显放慢了速度。该效应归因于与大分子内的区域中的分隔有关的内部摩擦。我们讨论了SCNPs与无序蛋白，特别是与内在无序蛋白的结构和动力学相似性。两种情况下的高内部摩擦似乎都与内部区域的存在有关。