Kim Jun Seok, Kodagahally Ravikumar, Strekowski Lucjan, Patonay Gabor
Department of Chemistry, University Plaza, Georgia State University, Atlanta, GA 30303, USA.
Talanta. 2005 Oct 31;67(5):947-54. doi: 10.1016/j.talanta.2005.04.025.
Near-infrared (NIR) bis(heptamethine cyanine) (BHmC) dyes containing a flexible polymethylene linker between the two cyanine subunits are a novel class of compounds with versatile spectroscopic properties. The first bis-cyanine of this type is BHmC-10 (with a decamethylene bridge) that has been reported by us recently [G. Patonay, J.S. Kim, R. Kodagahally, L. Strekowski, Appl. Spectrosc., in press]. As part of this work, additional bis-cyanines BHmC-4, BHmC-6, and BHmC-8 were synthesized and their spectral properties were evaluated for the dyes free in solution and in the presence of human serum albumin (HSA). These bis-cyanines undergo H-type aggregation, mainly H-type intramolecular complexation between the two cyanine subunits, when free in aqueous solution. This H-type interaction in phosphate buffer (pH 7.2) is characterized by hypsochromic (H) absorption at 700nm, low extinction coefficient, and low fluorescence quantum yield. By contrast, an analogous monomeric cyanine exhibits strong fluorescence under similar conditions. Upon binding with HSA, the fluorescence of BHmC-6 changes negligibly, that for BHmC-8 shows a slight increase, and the fluorescence of BHmC-4 is greatly increased. It is suggested that BHmC-4 binds with HSA in the open form exclusively, while the H-type intramolecular interaction in BHmC-6 is mostly retained in the complex with HSA. Bis-cyanine BHmC-4 may be of significant bioanalytical utility due to its negligible fluorescence in aqueous solution and a strong increase in fluorescence upon binding with a protein.
近红外（NIR）双（七甲川花菁）（BHmC）染料在两个花菁亚基之间含有一个柔性聚亚甲基连接基，是一类具有多种光谱性质的新型化合物。我们最近报道了此类的首个双花菁BHmC - 10（带有一个十亚甲基桥）[G. 帕托奈、J.S. 金、R. 科达加哈利、L. 斯特雷科夫斯基，《应用光谱学》，即将发表]。作为这项工作的一部分，合成了另外的双花菁BHmC - 4、BHmC - 6和BHmC - 8，并对其在溶液中以及在人血清白蛋白（HSA）存在下的光谱性质进行了评估。这些双花菁在水溶液中游离时会发生H型聚集，主要是两个花菁亚基之间的H型分子内络合。在磷酸盐缓冲液（pH 7.2）中的这种H型相互作用的特征是在700nm处有蓝移（H）吸收、低消光系数和低荧光量子产率。相比之下，类似的单体花菁在相似条件下表现出强荧光。与HSA结合后，BHmC - 6的荧光变化可忽略不计，BHmC - 8的荧光略有增加，而BHmC - 4的荧光大幅增加。有人认为，BHmC - 4仅以开放形式与HSA结合，而BHmC - 6中的H型分子内相互作用在与HSA形成的复合物中大多得以保留。双花菁BHmC - 4因其在水溶液中荧光可忽略不计且与蛋白质结合后荧光大幅增加，可能具有重要的生物分析用途。
