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Bisphenol A and its analogues have carcinogenic potentials and toxicities. However, there are lacks of studies elucidating gene toxic interactions of bisphenols with DNA. In this work, the binding modes of five bisphenol compounds with calf thymus DNA were characterized. The multi-spectroscopic experimental results indicated that the fluorescence quenching of bisphenols by calf thymus DNA point to groove binding. The ultraviolet visible and circular dichroism spectral data displayed that bisphenols partly induced conformational changes of calf thymus DNA. In addition, the binding constants of bisphenol A, diphenolic acid, bisphenol AF, bisphenol AP, bisphenol fluorine with calf thymus DNA obtained from fluorescence emission spectra were 1.09 × 10 4 , 3.65 × 10 4 , 4.46 × 10 4 , 1.69 × 10 4 , 4.49 × 10 4 L mol −1 at 298.15 K, which indicated that the multi-noncovalent binding forces were involved in the binding processes. In silico investigations indicated that DNA has the preferable binding sites binding with bisphenols by minor groove binding and electrons transfer from DNA bases to bisphenols occurred. In addition, the structural differences of these five bisphenols partly affected the binding ability of them with DNA. [ABSTRACT FROM AUTHOR]

Herein, we studied the binding interactions between hydroxylated single-walled carbon nanotubes and hemoglobin and myoglobin by the use of multi-spectral techniques and molecular modeling. The ultraviolet–vis absorbance and circular dichroism spectral results indicated that the binding interactions existed between hydroxylated single-walled carbon nanotubes and hemoglobin/myoglobin. These binding interactions partially affected the soret/heme bands of hemoglobin and myoglobin. The secondary structures of hemoproteins were partially destroyed by hydroxylated single-walled carbon nanotubes. Fluorescence studies suggested that the complexes formed between hydroxylated single-walled carbon nanotubes and hemoglobin/myoglobin by hydrogen bonding, hydrophobic, and π–π stacking interactions. In addition, molecular modeling analysis well supported the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The interactions between human hemoglobin and orange I (or orange II) were investigated by UV/vis absorption, circular dichroism, fluorescence spectra techniques, and molecular modeling method. Orange I and orange II effectively quenched the intrinsic fluorescence of human hemoglobin by static quenching. The processes of the binding orange I and orange II on human hemoglobin were spontaneous molecular interaction procedure with hydrogen bonds, van der Waals force, hydrophobic and electrostatic interactions according to van’t Hoff equation and molecular modeling. There is a single class of binding site of orange I (orange II) in human hemoglobin and the molecular modeling study shows that orange I and orange II are dipped into α2 chain. The results of CD, synchronous fluorescence and three-dimensional fluorescence spectra indicated a small loss of α-helical secondary structure of human hemoglobin induced by orange I and orange II. [Copyright &y& Elsevier]

Abstract: The nature of the interaction between human hemoglobin and C.I. acid red 27 was investigated systematically by ultraviolet–vis absorbance, circular dichroism, fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques at pH 7.40. The quenching mechanism, binding constants, and the number of binding sites were determined by the quenching of human hemoglobin fluorescence in presence of C.I. acid red 27. The results showed that the nature of the quenching was of static type and the process of binding acid red 27 on human hemoglobin was a spontaneous molecular interaction procedure. The electrostatic and hydrophobic interactions played a major role in stabilizing the complex; The distance r between donor and acceptor was obtained to be 4.40nm according to Förster’s theory; The effect of acid red 27 on the conformation of human hemoglobin was analyzed using synchronous fluorescence, circular dichroism and three-dimensional fluorescence spectra. [Copyright &y& Elsevier]

Abstract: The interaction between imidacloprid (IMI) and human serum albumin (HSA) was investigated using fluorescence and UV/vis absorption spectroscopy. The experimental results showed that the fluorescence quenching of HSA by IMI was a result of the formation of IMI–HSA complex; static quenching was confirmed to result in the fluorescence quenching. The apparent binding constant K A between IMI and HSA at three differences were obtained to be 1.51×104, 1.58×104, and 2.19×104 Lmol−1, respectively. The thermodynamic parameters, ΔH° and ΔS° were estimated to be 28.44kJmol−1, 174.76Jmol−1 K−1 according to the van’t Hoff equation. Hydrophobic interactions played a major role in stabilizing the complex. The distance r between donor (HSA) and acceptor (IMI) was obtained according to fluorescence resonance energy transfer. The effect of IMI on the conformation of HSA was analyzed using synchronous fluorescence spectroscopy CD and three-dimensional fluorescence spectra, the environment around Trp and Tyr residues were altered. [Copyright &y& Elsevier]

Abstract: The binding interactions of lysozyme with 2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were investigated by UV–vis absorption, CD, fluorescence, synchronous fluorescence, and three-dimensional fluorescence spectra techniques under physiological pH 7.40. The binding constants, quenching mechanism, and the number of binding sites were determined by the quenching of lysozyme fluorescence in presence of chlorophenols. H-bonds and hydrophobic interactions played major roles in stabilizing the chlorophenols–lysozyme complex. The distances r between chlorophenols and lysozyme were calculated to be 1.94nm, 2.75nm, 3.54nm, and 3.76nm for 2-CP, 2,4-DCP, 2,4,6-TCP, and PCP, respectively. The effects of chlorophenols on the conformation of lysozyme were analyzed using CD, synchronous fluorescence and three-dimensional fluorescence spectra. [Copyright &y& Elsevier]