Analytical Sciences

Interactions of Lysozyme with 6-Amino-4-aryl-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles: a Fluorescence Quenching Study

Hui WU,* Shuqin LIAN,** Yang SHEN,** and Yu WAN**

*Department of Chemistry, Xuzhou Normal University, Xuzhou, Jiangsu 221116, P. R. China
**Key Lab. of Biotechnology on Medicinal Plants of Jiangsu Province, Xuzhou, Jiangsu 221116, P. R. China

The interactions between 6-amino-4-aryl-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile and lysozyme (LYSO) were investigated by using tryptophane fluorescence quenching and 6-amino-4-(2-hydroxyphenyl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile (1) was studied in detail because of its high water solubility. At different temperatures, the quenching constants K_SV, the binding constants K and the binding sites n of LYSO with 1 were determined and the thermodynamic parameters were calculated. The distance r between tryptophane residues and 1 was obtained according to the Forster mechanism of non-radiation energy transfer. Furthermore, synchronous fluorescence spectroscopy data indicated that the association between 1 and LYSO changed LYSO's conformation and that the hydrophobic interaction played a major role in 1-LYSO association. It was proved that the fluorescence quenching of LYSO by 1 was related to the formation of a 1-LYSO complex and to a non-radiation energy transfer.

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