Davenport L, Knutson J R, Brand L
Biochemistry. 1986 Mar 11;25(5):1186-95. doi: 10.1021/bi00353a037.
The two-state excited-state proton-transfer process for d-equilenin [d-3-hydroxyestra-1,3,-5(10),6,8-pentaen-17-one] and dihydroequilenin is found to depend both on pH and on proton acceptor concentration. Both the protonated and deprotonated forms of the excited molecule are fluorescent. As is the case for 2-naphthol, the excited-state pKa (pKa*) is substantially lower than the ground-state pKa. Fluorescence decay studies have been performed as a function of emission wavelength in aqueous solutions at pH 6.9 in the presence of acetate anion (0.1 M). At this pH, both back-reaction from the excited-state and ground-state heterogeneity are minimal. A monoexponential decay is found in the blue region of the spectrum and a biexponential decay on the red edge. The lifetimes measured across both regions are constant, with a negative preexponential term, characteristic of an excited-state reaction, evident at longer wavelengths. Decay-associated spectra (DAS), the preexponential terms associated with the measured lifetimes, have been acquired for these aqueous solutions. Equilenin and dihydroequilenin are found to adsorb to dimyristoyllecithin (DML) vesicles. Rates for excited-state proton transfer are greatly reduced when dihydroequilenin adsorbs to vesicles. The accessibility of the bound probe to acetate as a proton acceptor depends on the cholesterol content of the vesicles.
已发现去氢马萘雌酮 [d-3-羟基雌甾-1,3,-5(10),6,8-戊烯-17-酮] 和二氢去氢马萘雌酮的双态激发态质子转移过程既取决于pH值，也取决于质子受体浓度。激发态分子的质子化形式和去质子化形式均具有荧光性。与2-萘酚的情况一样，激发态pKa（pKa*）显著低于基态pKa。在pH 6.9且存在乙酸根阴离子（0.1 M）的水溶液中，已进行了作为发射波长函数的荧光衰减研究。在此pH值下，激发态和基态的非均质性的反向反应均最小。在光谱的蓝色区域发现单指数衰减，在红色边缘发现双指数衰减。在两个区域测量的寿命是恒定的，在较长波长处有一个负的指数前项，这是激发态反应的特征。已获取了这些水溶液的衰减相关光谱（DAS），即与测量寿命相关的指数前项。发现马萘雌酮和二氢去氢马萘雌酮可吸附到二肉豆蔻酰卵磷脂（DML）囊泡上。当二氢去氢马萘雌酮吸附到囊泡上时，激发态质子转移速率会大大降低。结合态探针对于作为质子受体的乙酸根的可及性取决于囊泡的胆固醇含量。
