Characterization of the Self-Assembly of meso-Tetra(4-sulfonatophenyl)porphyrin (H2TPPS4鈥?/sup>) in Aqueous Solutions
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- 作者：Javoris V. Hollingsworth ; Allison J. Richard ; M. Gra莽a H. Vicente ; Paul S. Russo
- 刊名：Biomacromolecules
- 出版年：2012
- 出版时间：January 9, 2012
- 年：2012
- 卷：13
- 期：1
- 页码：60-72
- 全文大小：785K
- 年卷期：v.13,no.1(January 9, 2012)
- ISSN：1526-4602
文摘
The aggregation of meso-tetra(4-sulfonatophenyl)porphyrin (H2TPPS4鈥?/sup>) 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 渭M solution concentrations) using a combination of complementary analytical techniques. UV鈥搗is 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 H2TPPS4鈥?/sup>, 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 H4TPPS2鈥?/sup> species self-assembles, leading to the formation of particularly stable aggregates bearing 25 卤 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.