Institut Laue-Langevin, B.P. 156, F-38042 Grenoble CEDEX 9, France.
J Phys Chem B. 2010 Feb 11;114(5):1751-6. doi: 10.1021/jp9064455.
Small-angle neutron scattering (SANS) experiments were carried out to investigate the structure of aqueous (D(2)O) G4 PAMAM dendrimer solutions as a function of molecular protonation and dendrimer concentration. Our results indicate unambiguously that, although the radius of gyration R(G) remains nearly invariant, the dendrimer radial density profile rho(r) decreases in the dendrimer core with a continuous increase in protonation. This discovery also suggests that R(G), which is commonly adopted by numerous simulation and experimental works in describing the global dendrimer size, is not suitable as the index parameter to characterize the dendrimer conformation change. We also found that R(G) and rho(r), for dendrimers dissolved in both neutral and acidified solutions, remain nearly constant over the studied concentration range. We further demonstrate that the outcome of the widely used Guinier method is questionable for extracting R(G) in the concentration range studied. Our results reveal the polymer colloid structural duality as benchmarks for future experimental and theoretical studies and provide a critical step toward understanding drug encapsulation by ionic bonds.
小角中子散射（SANS）实验研究了质子化和树枝状分子浓度对水溶液（D（2）O）G4 PAMAM 树枝状分子溶液结构的影响。我们的结果明确表明，尽管回转半径 R（G）几乎保持不变，但随着质子化的不断增加，树枝状分子的径向密度分布 ρ（r）在树枝状分子核心中减小。这一发现还表明，R（G）被广泛应用于大量的模拟和实验工作来描述整个树枝状分子的大小，它不适合作为描述树枝状分子构象变化的指标参数。我们还发现，在研究的浓度范围内，中性和酸化溶液中溶解的树枝状分子的 R（G）和 ρ（r）几乎保持不变。我们进一步证明，在研究的浓度范围内，广泛使用的 Guinier 方法提取 R（G）的结果是值得怀疑的。我们的结果揭示了聚合物胶体结构的双重性，为未来的实验和理论研究提供了基准，并为理解离子键包封药物提供了关键的一步。
