Investigation On The Supramolecular Assembling, Regulating Of Cyanine Dyes Templated By Transferrin

Cyanine dyes has a special photophysical and photochemical properties that are strongly sensitive to the nature of the surrounding medium. This unique properties, making it as a phototoxic agent, photosensitizer and biological molecular probe, and are widely used in photodynamic therapy and in the field of biological medicine. The inherent law of the interaction between transferrin(Tf) and cyanine dyes with different structure at the molecular level are investigated, which is helpful to provide a new thought for building Tf targeted cyanine dyes to achieve the specific identification of tumor cells. In addition, the interaction between fulvic acid(FA) and cyanine dyes through various spectroscopic techniques to further clarify the specific recognition mechanism between them is also discussed in this paper, the last, we put forward a kind of simple operation, high-sensitivity and visible method for the detection of pharmacodynamic mechanism of FA Its main results are as follows:The mechanisms of interaction between Tf with cyanine dyes are investigated by various spectroscopic techniques and molecular dynamic docking. The results shows that cyanine dyes MTC, ETC and PTC have a higher binding affinity to Tf with an intrinsic binding constant, Ka, in the order of 104~109 M-1, that depends on the temperatures and p H.The binding of cyanine dyes to Tf induced a conformational changes in transferrin, with a major increment of α-helix content of Tf. Molecular modeling elucidates that cyanine dyes MTC, ETC and PTC bind to residues located in the N-lobe of Tf.Two novel cyanine dyes DMSA and DMSB are getting from the design of the structure of cyanine dye MTC, and the mechanisms of interaction between them and transferrin are portrayed by means of various spectroscopic techniques. It is found that there is a strong interaction of DMSA and DMSB with Tf, the binding constants Ka can reach to the order of 109 M-1, and the binding constants of DMSA is up to 10000 times compared with the binding constants of DMSB, which mainly depends on the different structure of dyes. Furthermore, structural analysis indicate that DMSA and DMSB binding results in a decreased of α-helix content.Supramolecular assembly and chiral inducement of cyanine dyes induced by FA is investigated by using UV-vis absorption and circular dichroism(CD) spectra. The result suggests that FA can induce cyanine dyes from J-aggregation to monomer along with different colors change and has strong affinity with cyanine dye monomer. The association of dyes with FA gives rise to the dyes aggregation CD signals.