Patonay Gabor, Kim Jun Seok, Kodagahally Ravikumar, Strekowski Lucjan
Department of Chemistry, University Plaza, Georgia State University, Atlanta, Georgia 30303, USA.
Appl Spectrosc. 2005 May;59(5):682-90. doi: 10.1366/0003702053945976.
A newly synthesized near-infrared (NIR) bis(heptamethine cyanine) dye 7 was evaluated for its utility as a non-covalent label for proteins. This dye forms inter- and intramolecular H-aggregates in polar solvents, even at very low concentrations. The intramolecular dimeric form of the dye can be described as a clam-shell complex with two interacting hydrophobic carbocyanine moieties. In this intramolecular H-aggregate, the chromophore has a low extinction coefficient and low fluorescence quantum yield. In aqueous solution, in the absence of human serum albumin (HSA), dye 7 has characteristic absorption bands at 792 and 435 nm, and its fluorescent emission is significantly diminished in comparison to that in methanol or when compared to its monomeric equivalent 5. Dye 7 seems to be more advantageous than its monomeric counterpart 5 as a non-covalent label for biomolecules. Upon addition of HSA, the H and D bands are decreased and the monomeric band is increased, with concomitant increase in fluorescence intensity, suggesting that clam-shell H-aggregates open up in the complex with HSA. The binding stoichiometry is 1:1. The main advantage of this dimeric dye as a non-covalent label is that the free dye has negligible fluorescence.
一种新合成的近红外（NIR）双（七甲川花菁）染料7作为蛋白质的非共价标记物的效用进行了评估。这种染料即使在极低浓度下，在极性溶剂中也会形成分子间和分子内的H-聚集体。该染料的分子内二聚体形式可描述为具有两个相互作用的疏水碳菁部分的蛤壳状复合物。在这种分子内H-聚集体中，发色团具有低消光系数和低荧光量子产率。在水溶液中，在没有人血清白蛋白（HSA）的情况下，染料7在792和435nm处有特征吸收带，与在甲醇中的情况相比或与其单体等效物5相比，其荧光发射明显减弱。染料7作为生物分子的非共价标记物似乎比其单体对应物5更具优势。加入HSA后，H和D带降低，单体带增加，同时荧光强度增加，这表明蛤壳状H-聚集体在与HSA的复合物中打开。结合化学计量比为1:1。这种二聚体染料作为非共价标记物的主要优点是游离染料的荧光可忽略不计。
