Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
J Am Chem Soc. 2009 Oct 28;131(42):15152-9. doi: 10.1021/ja903548m.
The kinetic properties of the self-assembly of hydrophilic Keplerate-type polyoxometalate (POM) {Mo(72)Fe(30)} macroanions into single-layer, vesicle-like blackberry structures in solutions were monitored by the static and dynamic laser light scattering techniques. In the presence of additional electrolytes, an obvious lag period at the initial stage of self-assembly was observed, followed by a fast increase of the scattered intensity. The whole kinetic curve is sigmoidal with a lag phase. A two-step nucleation-growth mechanism is proposed to explain this lag phase: the {Mo(72)Fe(30)} macroanions slowly associate into oligomers (mostly dimers), which are the thermodynamically unfavorable intermediates, at the initial stage; once the oligomers reach a critical concentration, the blackberry formation process is accelerated. Analytical ultracentrifugation (AUC) was used to confirm the oligomeric state in {Mo(72)Fe(30)} solution during the lag period. The length of the lag period is dependent on temperature, ionic strength, and the valent states of the additional salts, as well as the solvent content. The kinetics (including the lag period) of the blackberry formation of the {Mo(72)Fe(30)} macroanions show similarities to the self-assembly of virus capsid proteins (which are also soluble macroions) into spherical capsid shells, suggesting possible connections between the self-assembly behaviors of inorganic species and biological macromolecules.
亲水性 Keplerate 型多金属氧酸盐（POM）{Mo(72)Fe(30)} 大分子阴离子在溶液中自组装成单层、囊泡状黑莓结构的动力学性质通过静态和动态激光光散射技术进行了监测。在额外电解质的存在下，观察到自组装初始阶段明显的滞后期，随后散射强度迅速增加。整个动力学曲线呈 S 形，具有滞后相。提出了两步成核生长机制来解释这种滞后相：在初始阶段，{Mo(72)Fe(30)} 大分子阴离子缓慢缔合成低聚物（主要是二聚体），这是热力学上不利的中间体；一旦低聚物达到临界浓度，黑莓形成过程就会加速。分析超速离心（AUC）用于在滞后期确认{Mo(72)Fe(30)}溶液中的低聚物状态。滞后期的长度取决于温度、离子强度、外加盐的价态以及溶剂含量。{Mo(72)Fe(30)}大分子阴离子黑莓形成的动力学（包括滞后期）与病毒衣壳蛋白（也是可溶性大分子）自组装成球形衣壳相似，表明无机物种和生物大分子的自组装行为之间可能存在联系。
