Margalit R, Cohen S
Biochim Biophys Acta. 1983 Dec 21;736(2):163-70. doi: 10.1016/0005-2736(83)90280-8.
Two processes of porphyrins in heterogeneous systems containing aqueous and membrane phases have been studied with hematoporphyrin and hematoporphyrin derivative: Dimerization equilibrium in the aqueous phases and porphyrin-membrane binding equilibrium using liposomes as models for biological membranes. The interrelationship of aqueous aggregations and membrane binding was probed and the porphyrin aggregation state in the membrane, at equilibrium, was assessed. Fluorimetric techniques were employed. The dimerization equilibrium constants, at neutral pH and 37 degrees C were found to be 2.8 X 10(5) M-1 and 1.9 X 10(6) M-1 for hematoporphyrin and its derivative, respectively. Over a porphyrin concentration range going from monomer-dominant to dimer-dominant systems, we have found that only monomers are bound to the membrane. The respective monomer-liposome binding constants, found to be independent of the initial monomer/dimer distribution in the aqueous phase, were determined to be 1.6 X 10(3) M-1 and 4.1 X 10(3) M-1 at neutral pH and 37 degrees C for hematoporphyrin and its derivative, respectively. The monomer-liposome interaction was found to perurb the initial monomer/dimer distribution in the aqueous phase, so that the monomers residing at equilibrium in the membrane originate from both monomers and dimers in the aqueous phase.
利用血卟啉和血卟啉衍生物，研究了在含有水相和膜相的非均相体系中卟啉的两个过程：水相中的二聚化平衡以及使用脂质体作为生物膜模型的卟啉 - 膜结合平衡。探讨了水相聚集与膜结合之间的相互关系，并评估了平衡时膜中卟啉的聚集状态。采用了荧光技术。在中性pH和37℃条件下，血卟啉及其衍生物的二聚化平衡常数分别为2.8×10⁵ M⁻¹和1.9×10⁶ M⁻¹。在从单体主导体系到二聚体主导体系的卟啉浓度范围内，我们发现只有单体与膜结合。在中性pH和37℃条件下，血卟啉及其衍生物各自的单体 - 脂质体结合常数分别为1.6×10³ M⁻¹和4.1×10³ M⁻¹，且发现其与水相中初始单体/二聚体分布无关。发现单体 - 脂质体相互作用会扰乱水相中初始单体/二聚体分布，因此平衡时存在于膜中的单体既来源于水相中的单体，也来源于水相中的二聚体。
