Department of Chemistry and Macromolecular Studies Group, Louisiana State University, Baton Rouge, Louisiana 70803, United States.
Biomacromolecules. 2012 Jan 9;13(1):60-72. doi: 10.1021/bm201078d. Epub 2011 Dec 9.
The aggregation of meso-tetra(4-sulfonatophenyl)porphyrin (H(2)TPPS(4-)) in phosphate solutions was investigated as a function of pH, concentration, time, ionic strength, and solution preparation (either from dilution of a freshly prepared 2 mM stock or by direct preparation of μM solution concentrations) using a combination of complementary analytical techniques. UV-vis and fluorescence spectroscopy indicated the formation of staggered, side-by-side (J-type) assemblies. Their size and self-associative behavior were determined using analytical ultracentrifugation and small-angle X-ray scattering. Our results indicate that in neutral and basic solutions of H(2)TPPS(4-), porphyrin dimers and trimers are formed at micromolar concentrations and in the absence of NaCl to screen any ionic interactions. At these low concentrations and pH 4, the protonated H(4)TPPS(2-) species self-assembles, leading to the formation of particularly stable aggregates bearing 25 ± 3 macrocycles. At higher concentrations, these structures further organize or reorganize into tubular, rod-like shapes of various lengths, which were imaged by cryogenic and freeze-fracture transmission electron microscopy. Micron-scale fibrillar aggregates were obtained even at micromolar concentrations at pH 4 when prepared from dilution of a 2 mM stock solution, upon addition of NaCl, or both.
研究了在磷酸盐溶液中，meso-四（4-磺基苯基）卟啉（H（2）TPPS（4-））的聚集情况，其功能取决于 pH 值、浓度、时间、离子强度以及溶液的制备方式（是通过稀释新制备的 2mM 储备液还是直接制备μM 溶液浓度），使用了一系列互补的分析技术。紫外可见吸收光谱和荧光光谱表明形成了交错、并排（J 型）组装体。使用分析超速离心和小角 X 射线散射确定了它们的大小和自缔合行为。我们的结果表明，在 H（2）TPPS（4-）的中性和碱性溶液中，在没有 NaCl 屏蔽任何离子相互作用的情况下，在微摩尔浓度下形成了卟啉二聚体和三聚体。在这些低浓度和 pH 值为 4 的情况下，质子化的 H（4）TPPS（2-）物种自组装，导致形成了特别稳定的带有 25 ± 3 个大环的聚集体。在较高浓度下，这些结构进一步组织或重新组织成各种长度的管状、棒状形状，通过低温和冷冻断裂透射电子显微镜进行了成像。甚至在 pH 值为 4 时，即使在微摩尔浓度下，从 2mM 储备液稀释、添加 NaCl 或两者都添加的情况下，也可以得到微米级的纤维状聚集体。
