Vinogradov S A, Wilson D F
Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia 19104, USA.
Chemistry. 2000 Jul 3;6(13):2456-61. doi: 10.1002/1521-3765(20000703)6:13<2456::aid-chem2456>3.0.co;2-p.
Polyglutamic dendritic porphyrins of the general formula H2PophGlu(N)OR (H2Porph = free-base meso-tetra-4-carboxyphenylporphyrin (H2TCPP), Glu=dendrimer layer composed of L-glutamates, N= 1-3: dendrimer generation number, R = terminal group (All, H)) were synthesized and characterized with NMR and MALDI-TOF mass spectroscopy. The free-acid terminated compounds were found to be highly soluble in water, with both their absorption and fluorescence spectra dependent on pH. The value of the porphyrin mono-protonation constant, measured by fluorescence rationing, increased monotonously in the studied series of dendrimers (pK3=6.31. 6.70, and 6.98, for N=1, 2, 3, respectively). For the largest dendrimer, H2PorphGlu(3)OH, pK3 was found shifted by almost two pH units relative to the non-modified H2Porph. The second protonation constant (K4) was much less affected by the dendritic substituents. At pH values less than 3.5 there were noticeable changes in fluorescence intensity and quantum yield even for the highly soluble H2PorphGlu(3)OH. This suggests that interactions between individual dendritic molecules in solution are favored by full protonation of the peripheral glutamic carboxyls. The "dendrimer-protected" porphyrins are convenient fluorescent pH sensors in the biological pH range.
合成了通式为H2PophGlu(N)OR的聚谷氨酸树枝状卟啉（H2Porph = 游离碱中位 - 四 - 4 - 羧基苯基卟啉（H2TCPP），Glu = 由L - 谷氨酸组成的树枝状聚合物层，N = 1 - 3：树枝状聚合物代数，R = 端基（All，H）），并通过核磁共振和基质辅助激光解吸电离飞行时间质谱对其进行了表征。发现游离酸封端的化合物在水中高度可溶，其吸收光谱和荧光光谱均依赖于pH值。通过荧光定量测量的卟啉单质子化常数的值在研究的树枝状聚合物系列中单调增加（对于N = 1、2、3，pK3分别为6.31、6.70和6.98）。对于最大的树枝状聚合物H2PorphGlu(3)OH，发现pK3相对于未修饰的H2Porph几乎偏移了两个pH单位。第二个质子化常数（K4）受树枝状取代基的影响要小得多。在pH值小于3.5时，即使对于高度可溶的H2PorphGlu(3)OH，荧光强度和量子产率也有明显变化。这表明溶液中单个树枝状分子之间的相互作用因外围谷氨酸羧基的完全质子化而受到促进。“树枝状聚合物保护”的卟啉在生物pH范围内是方便的荧光pH传感器。
