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The study of molecular derivatives of biological dyes is of great importance for the green transformation of the printing, dyeing, and textile industries. In this study, B3LYP density functional methods are used to optimize the geometric configuration of the selected molecules and to explore the relationship between the structure and color of biological dye molecules and their color mechanism. This study focuses on the analysis of polyenes, quinones, indoles, and azide biological dyes in colors commonly used in the textile industry: blue, yellow, purple, red, green, and so on. Quantum chemical investigations show that the conjugate structure of a biological dye is directly related to its color and that the group or structure affecting the conjugate structure will in many cases cause a change in color. In addition, time-dependent density functional theory spectral calculations with the CAM-B3LYP functional for UV-Vis spectra show that in the visible band, the color of the remaining band after subtracting the absorption wavelengths was exactly the same as the color of the pigment. These results indicate that the color of the pigment is exactly complementary to the light absorption color of the material. Our study provides theoretical guidance for the design of molecular derivatives of biological dyes and is expected to promote the green transformation of the textile, printing, and dyeing industries to a certain extent. [ABSTRACT FROM AUTHOR]

6PPD and its oxidation product, 6PPD-quinone have garnered widespread attention due to their adverse effects on aquatic ecosystems and human health, and are recognized as emerging pollutants. In this study, we investigated the interaction mechanism between 6PPD/6PPD-quinone and human serum albumin (HSA) through various experiments. Experimental findings reveal that the IC 50 values of 6PPD-quinone and 6PPD against HEK293T cells were 11.78 and 40.04 μM, respectively. Additionally, the cytotoxicity of these compounds was regulated by HSA, displaying an inverse correlation with their binding affinity to HSA. Furthermore, 6PPD/6PPD-quinone can spontaneously insert into site I on HSA, forming a binary complex that induces changes in the secondary structure of HSA. However, their effects on the esterase-like activity of HSA exhibit a dichotomy. While 6PPD activates the esterase-like activity of HSA, 6PPD-quinone inhibits it. Molecular docking analyses reveal that both 6PPD and 6PPD-quinone interact with many amino acid residues on HSA, including TRP214, ARG222, ARG218, ALA291, PHE211. The π electrons on the benzene rings of 6PPD/6PPD-quinone play pivotal roles in maintaining the stability of complexes. Moreover, the stronger binding affinity observed between 6PPD and HSA compared to 6PPD-quinone, may be attributed to the larger negative surface potential of 6PPD., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)