Simultaneous Occurrence of Energy Transfer and Photoinduced Electron Transfer in Interactions of Hen Egg White Lysozyme with 4‐Nitroquinoline‐1‐Oxide

Abstract

The carcinogenic drug 4-nitroquinoline-1-oxide (4NQO) has been found to bind with the protein hen egg white lysozyme as evident from fluorescence quenching experiments. The binding constant and stoichiometry have been determined. The values of the thermodynamic parameters indicate that the interaction is an enthalpy-driven spontaneous phenomenon. The experimental value of change in free energy is similar to that obtained from the docking study. The far UV circular dichroism spectra show some changes in the secondary structure of protein. The high value of bimolecular quenching constant leads to the possibility of Förster resonance energy transfer (FRET). Along with FRET, the photoinduced electron transfer (PET) from tryptophan residue of protein to 4NQO has also been evident from the transient absorption spectra obtained in laser flash photolysis experiments. The simultaneous occurrence of FRET and PET is the key factor for quenching of intrinsic fluorescence of the protein as it binds with the drug.

Spectroscopic exploration of drug–protein interaction: a study highlighting the dependence of the magnetic field effect on inter-radical separation distance formed during photoinduced electron transfer

“…52 A similar case of absence of MF effect is also obtained by our group while studying the interaction of 4-nitroquinoline-1-oxide and hen egg white lysozyme as the donor-acceptor separation distance is about 3.1 Å, which inhibits spin conversion. 60 On the contrary, in the present case of AD-HSA system the separation distance (13.5 Å) between the donor and the acceptor moieties of PET is tting for appreciable MF effect. Our previous report shows that during interaction with HSA, two other acridine derivatives, viz.…”

Oxidative Interaction between OxyHb and ATP: A Spectroscopic Study

“…With the help of K SV and fluorescence lifetime (τ 0 ) values, a k q value has been determined from eq 4 which is 1.449 × 10 12 M −1 s −1 . The upper limit of k q is 10 10 M −1 s −1 for a diffusion control phenomenon from eq 5, 31 which indicates that the quenching is static in nature, suggesting the formation of a ground state complex.…”

Interaction of Retinoic Acid Radical Cation with Lysozyme and Antioxidants: Laser Flash Photolysis Study in Microemulsion

“…Tyr and Trp, the aromatic amino acid residues of proteins, are prime targets for oxidation by various forms of reactive oxidative species (ROS) . Previous reports indicated that Lyso could be attacked by ROS via the interaction of ROS with its Tyr and Trp residues . The ability of ATRA •+ to react with Tyr and Trp was evaluated in this study.…”

“…To evaluate the potential of ATRA •+ to damage biomolecules, we herein investigated the interactions of ATRA •+ with Lyso and two amino acids. Lyso was chosen as a model protein because of its extensive use in the studies of photodamage of proteins (35)(36)(37)(38)(39)(40). Result shows that the decay of ATRA •+ at 590 nm is accelerated by the presence of Lyso at pH 7.4, indicating that ATRA •+ can interact with Lyso (Fig.…”