A Spectroscopic Study of the Interaction between Cyanine Dyes with Different Skeleton Structures and Transferrin

Abstract

Human serum transferrin (hTf) has been exploited as a biocarrier for targeted drugs to cancer cells where transferrin receptors are expressed at high levels. In this study, cyanine dyes DMSA and DMSB with a similar main core structure were selected to evaluate the effects of heterocycle on binding with hTf by spectroscopic methods. Fluorescence spectral results have shown that DMSB, which contains a selenazole ring, had a strong affinity binding with transferrin, up to 10 4 -fold higher than DMSA, which contains a thiazole ring. This difference may be attributed to the larger molecular volume of selenazole compared with DMSA. Binding distance between cyanine dyes and hTf demonstrated that the non-radioactive energy transfer mechanism was also involved in the fluorescence quenching of protein. Furthermore, DMSB-binding gave rise to a greater decrease of the α-helix content of hTf than DMSA suggesting that hTf, which shows a looser structure binding with DMSB, increased polarity around the tryptophan residues of hTf, which was confirmed by circular dichroism and synchronous fluorescence spectroscopy. The study provides a certain theoretical basis for the design of cyanine dyes as biomolecular probe to target drugs for hTf.

Ethyl‐substituted Thioflavin T as a Fluorescent Probe for Detecting the Conformation of Transferrin

“…Although the identification and monitoring of Tf conformation is of great importance in a wide range of research fields, the characterization methods of Tf conformation have so far been limited. Both X‐ray crystallography and NMR are known to require a large amount of sample material to provide accurate structural information . However, the former only informs a static configuration state under appropriate crystallization conditions, while the latter is complicated to interpret large protein data.…”