A novel solvatochromic fluorescent molecule, 9,9-dibutyl-7-(dimethylamino)-2-fluorenesulfonate 2 was synthesized from 2-nitrofluorene in moderate yield. The fluorescence spectra of 2 and 7-(dimethylamino)-2-fluorenesulfonate 1 shift to shorter wavelengths as the polarity of the medium decreases. Both 1 and 2 bind to hydrophobic sites of human serum albumin (HSA). The apparent binding constants were determined by fluorescence titration to be 0.37 × 106 M−1 for 1 and 2.2 × 106 M−1 for 2. The energy of the Trp-214 fluorescence of HSA is transferred to the HSA-bound fluorophores with near 100% efficiency. The covalent bonding of acrylodan (AC) to Cys-34 has little effect on the binding affinity of 2 to HSA or fluorescent behavior of HSA-bound 2. Bound 2 also has little effect on the fluorescence of AC, but 2→AC and Trp-214→2→AC resonance energy transfers were observed. Competitive binding between the fluorene compounds and other ligands such as 1-anilino-8-naphthalenesulfonate, aspirin, S-(+)-ibuprofen and phenylbutazone were also studied fluorometrically. The results indicated that the primary binding site of 2 to HSA is site II in domain IIIA, whereas 1 binds to site I in domain IIA, but a different region from the phenylbutazone binding site. Because of its large molar absorptivity, strong fluorescence, sensitivity to its environment, and high binding constant to HSA, 2 can be used successfully in the study of proteins and their binding properties.
一种新型溶剂染色荧光分子,9,9-二丁基-7-(
二甲氨基)-2-
氟烯
磺酸盐2是以中等产率从2-硝基
氟烯合成的。分子2和7-(
二甲氨基)-2-
氟烯
磺酸盐1的荧光光谱在介质极性降低时向更短波长移动。两者均与人
血清白蛋白(H
SA)的疏
水位点结合。通过荧光滴定法测定的表观结合常数为1的0.37 × 10^6 M−1和2的2.2 × 10^6 M−1。H
SA的色
氨酸-214的荧光能量几乎以100%的效率转移到H
SA结合的荧光团上。
丙烯酸丹(AC)与半胱
氨酸-34的共价结合对2与H
SA的结合亲和力或H
SA结合的2的荧光行为几乎没有影响。结合的2对AC的荧光也几乎没有影响,但观察到了2→AC和色
氨酸-214→2→AC的共振能量转移。还通过荧光法研究了
氟烯化合物与其他
配体(如1-
苯胺-8-
萘磺酸盐、
阿司匹林、S-(+)-
布洛芬和苯基丁挫嗪)的竞争结合。结果表明,2与H
SA的主要结合位点是区域IIA中的位点II,而1则结合在区域IIA中的位点I,但与苯基丁挫嗪的结合位点不同。由于其较大的摩尔吸光度、强荧光、对环境的敏感性以及对H
SA的高结合常数,2可以成功用于蛋白质及其结合特性的研究。