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ItemSpectroscopic analysis of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol binding to blood plasma albumin(Springer-Verlag Wien, 2022)Binding of 2-(5-mercapto-1,3,4-oxadiazol-2-yl)-6-methylquinolin-4-ol (C1), a biologically active substance, to bovine blood plasma albumin (BSA) at 293, 298, and 303 K was studied using fluorescence (steady state, synchronous, excitation/emission matrix) and FT-IR spectroscopy methods. The experimental results showed that C1 causes fluorescence quenching of BSA through both static and dynamic quenching mechanisms. The thermodynamic parameters, enthalpy and entropy change, for the static quenching were calculated to be − 35.73 kJ mol−1 and − 35.34 J mol−1 K−1, which indicated that hydrogen bonding and van der Waals interactions were the predominant intermolecular forces regulating C1–BSA interactions. Distance between donor and acceptor (2.14, 2.26, and 2.30 nm) depending on the temperature, obtained from intrinsic Förster resonance energy transfer calculations, revealed the static quenching mechanism of BSA fluorescence in 0–3.0 × 10−5 mol/dm3 concentration range of C1. The micro-environmental and conformational changes in BSA structure, established by synchronous, excitation/emission matrices and FT-IR spectra showed the changes in the BSA secondary structure.
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ItemFTIR ATR SPECTRAL AND THEORETICAL VIBRATIONAL STUDIES OF URACIL IN DIMETHYLSULFOXIDE OR DIETHYLSULFOXIDE SOLUTIONS(Pleiades Publishing, 2022)In this work the solutions of uracil in pure dimethylsulfoxide (DMSO) and diethylsulfoxide (DESO) have been studied by both FTIR ATR spectroscopy and quantum-chemical calculations. The remarkable changes were observed in the C=O, N–H (1745-1630 cm–1) and in S=O stretching region (1100-970 cm–1). The changes of the aforementioned frequencies are explained by the destruction of self-associates of sulfoxides in the presence of uracil and formation of uracil/DMSO (DESO) complexes via hydrogen-bond of the uracil N–H group with the S=O group of sulfoxides. Structural, energetic and vibrational characteristics for the hydrogen-bonded molecular complex of uracil/DMSO (DESO) in the gas phase and in solution have been studied by DFT and ab initio MO theory. It revealed, that the uracil/DMSO complex is more compact compared with uracil/DESO complex due to additional hydrogen bonds via C=O group of uracil and –CH group of DMSO. The observed wavenumbers are in good agreement with calculated wavenumbers.