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Three new N,N′,N′′-trisubstituted guanidine derivatives (L1, L2 and L3) were synthesized and characterized using NMR and mass spectral studies. The structures of these ligands have been confirmed using single-crystal XRD studies. The interactions between these ligands and calf-thymus DNA (CT-DNA) were investigated in vitro using different spectroscopic methods and molecular docking and simulation methods in a physiological buffer (pH 7.4). UV-Vis spectral titrations suggested the formation of an L2/CT-DNA complex. The addition of increasing amounts of CT-DNA enhanced the fluorescence of L2 with a binding constant on the order of 104 M−1, indicating fairly strong binding between them. Thermodynamic parameters ΔG0 < 0 and ‖ΔH0‖ < T‖ΔS0‖ suggested that the complexation is spontaneous and entropy-driven where hydrophobic interaction plays a dominant role in stabilizing the complex. Molecular docking and metadynamics simulation studies indicated partial intercalation of one of the phenyl rings between the base pairs of DNA, which is strongly supported by circular dichroism, viscosity measurements and KI quenching studies. [ABSTRACT FROM AUTHOR]

A new naked-eye chromogenic and fluorogenic probe KS5 has been developed for the detection of CN - ions in neat DMSO and H 2 O:DMSO (1:1 v/v) media. The probe KS5 exhibited selectivity towards CN - and F - ions in organic and high selectivity towards CN - ions in aquo-organic media resulting in a colour change from brown to colourless and a turn-on fluorescence response. The probe could able to detect CN - ions via a deprotonation process, which was conceived by consecutive addition of hydroxide and hydrogen ions and confirmed using 1 H NMR studies. The limit of detection (LOD) of KS5 towards CN - ions were in the range of 0.07-0.62 µM in both these solvent systems. Suppression of intra-molecular charge transfer (ICT) transition and photoinduced electron transfer (PET) process of KS5 by the added CN - ions are responsible for the chromogenic and fluorogenic changes observed, respectively. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations strongly supported the proposed mechanism along with the optical properties of the probe before and after the addition of CN - ions. To prove the practical applicability, KS5 was successfully utilized to detect CN - ions in cassava powder and bitter almonds as well as to determine CN - ions in various real water samples., 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 © 2023 Elsevier B.V. All rights reserved.)

UV-vis, fluorescence, circular dichroism (CD) and 1 H NMR spectroscopic techniques have been employed to explore the mode of binding of Mebendazole (MBZ) drug with calf thymus DNA (CT-DNA). UV-vis and fluorescence spectral studies suggested a complex formation between the drug and nucleic acid. The fluorescence of MBZ was found to enhance upon binding with CT-DNA through a ground state complex formation with K b in the order of 10 4 M -1 . The thermodynamic aspects indicated that the complex formation is a spontaneous process and an entropy-driven one. ΔH 0  > 0 and ΔS 0  > 0 revealed that hydrophobic interaction plays a dominant role in the stabilization of the complex. Competitive dye displacement assays with ethidium bromide (EB) and Hoechst 33258 dyes and viscosity measurements pointed out that MBZ binds with CT-DNA via intercalation mode, which is confirmed by CD and 1 H NMR spectral studies as well as denaturation studies. Molecular docking analysis could not match well with the experimental results. However, molecular simulation studies and the resultant free energy surface (FES) analysis clearly showed that the benzimidazole ring of MBZ intercalated between the base pairs of the nucleic acid, which is in excellent agreement with the results of the various biophysical experiments., 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 © 2023 Elsevier B.V. All rights reserved.)

A simple fluorescent probe (KS4) containing multiple reaction sites (phenolic -OH, imine and C = C bonds) is successfully synthesized and characterized using 1 H NMR, 13 C NMR, mass and single crystal XRD techniques. KS4 exhibits high selectivity towards CN - over a wide range of common anions in H 2 O:DMSO (1:1 v/v) leading to an amazing turn-on fluorescence at 505 nm via deprotonation of the phenolic -OH group. The limit of detection (1.3 µM) for CN - was much below the standard (1.9 µM) set by the World Health Organization (WHO). Stoichiometry of the interaction between KS4 and CN - was ascertained as 1:1 by the Job's plot method and the binding constant was determined to be 1.5x10 4 M -1 . Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) based theoretical insight has been appealed to understand the optical properties of KS4 before and after the addition of CN - ion. The probe shows respectable real-time applicability for qualitative detection of CN - in almond and cassava powder as well as quantification in real water samples with excellent recoveries (98.8 - 99.8%). In addition, KS4 is found to safe towards living HeLa cells and successfully applied to the detection of endogenous cyanide ions in HeLa cells., 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 © 2023 Elsevier Inc. All rights reserved.)

The interaction between oral contraceptive drug Ormeloxifene (ORM) and calf thymus DNA (CT-DNA) was studied using UV-Vis, fluorescence, circular dichroism (CD) and 1 H NMR spectral techniques under physiological buffer (pH 7.4). Competitive binding assays with ethidium bromide (EB) and Hoechst 33258, viscosity measurements, KI quenching studies, molecular docking and metadynamics simulation studies were also substantiated the spectroscopic results. ORM is found to binds in the minor groove of CT-DNA as evidenced by: (1) non-displacement of EB from EB/CT-DNA complex; (2) appreciable displacement of Hoechst 33258 from its CT-DNA complex; (3) slight alteration in the CD signal; (4) small shifts (Δδ < 0.033 ppm) without broadening in 1 H NMR signals and (5) the nearly equal extent of quenching of fluorescence of ORM by KI in the absence and presence of CT-DNA. Negative values of both enthalpy and entropy changes pointed out that the interaction between ORM and CT-DNA is governed mainly by H-bonding and van der Waals forces. Negative free energy change suggested a spontaneous interaction between ORM and CT-DNA. The free energy landscape of the binding process was computed using metadynamics simulation. The simulation study results disclosed that ORM binds to the minor groove of DNA through H-bonding and π-π stacking interactions. The results of molecular docking and simulation studies corroborate the available experimental data., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Remdesivir (REM) is an antiviral drug, which exercises its effect by targeting specifically RNA-dependent RNA polymerase. The interaction of REM with calf thymus DNA (CT-DNA) was investigated by multi-spectroscopic techniques (UV-Vis, fluorescence, circular dichroism and 31 P NMR) in combination with different biophysical experiments and metadynamics simulation studies. UV-Vis and fluorescence spectroscopic analysis indicated formation of a complex between REM and CT-DNA, whose binding constant is in the order of 10 4 M -1 . Competitive displacement assays with ethidium bromide (EB) and Hoechst 33258 shown that REM binds to CT-DNA via intercalation mode. Significant alteration in the band due to base stacking pairs at 274 nm in the circular dichroism spectrum, appreciable increase in relative viscosity of the biomolecule upon binding with REM and the results of potassium iodide quenching studies confirmed that REM intercalates into the base pairs of CT-DNA. Thermodynamic parameters revealed that the binding of REM to CT-DNA is a spontaneous process (ΔG 0  < 0) and the main force which holds them together in the REM/CT-DNA complex is electrostatic interaction (ΔH 0  < 0 and ΔS 0  > 0). The up-field shift in the 31 P NMR signal of REM on interaction with CT-DNA suggested that phenyl ring adjacent to the phosphate moiety of REM may involve in the intercalation process. This is well supported by the analysis of free energy surface landscape derived from metadynamics simulation studies., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Binding of voglibose (VOG), an alpha glucosidase inhibitor, with CT-DNA has been investigated using various spectroscopic techniques including UV-Vis, fluorescence and circular dichroism (CD) coupled with relative viscosity. Isothermal titration calorimetric studies have been used to calculate the thermodynamic parameters such as ΔH (0.0188 cal/mol), ΔS (63.3 cal/mol/K) and ΔG (-18.8 kcal/mol), which reveal that the binding is a spontaneous process and hydrophobic and H-bonding interactions play major roles in the binding process. Effect of ionic strength confirms the existence of hydrophobic interaction between VOG and CT-DNA. Competitive displacement assays with ethidium bromide (EB) and Hoechst 33258 suggest that VOG possibly binds on the surface of CT-DNA. Viscosity measurements also disclose that the binding could be mainly surface binding. Corroborating the experimental observations, metadynamics molecular simulation studies confirm that VOG binding on the surface of the DNA molecule through hydrophobic interactions and direct and water molecule mediated H-bonding., 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 © 2022 Elsevier B.V. All rights reserved.)