israel enoch | Karunya University (original) (raw)
Papers by israel enoch
Journal of Inclusion Phenomena and Macrocyclic Chemistry
Journal of Biological Physics, Jul 30, 2014
We report the binding of the drug raloxifene with Calf thymus DNA (ctDNA) and bovine serum albumi... more We report the binding of the drug raloxifene with Calf thymus DNA (ctDNA) and bovine serum albumin (BSA) in the presence and absence of β-cyclodextrin (β-CD) and explain the influence of β-cyclodextrin on the binding of the drug to macromolecules. UV-Vis absorption, fluorescence, proton nuclear magnetic resonance and two-dimensional rotating-frame nuclear overhauser effect spectroscopic techniques are used to study the stoichiometry and the binding strength of the complexes. Molecular modeling is used in combination with other techniques to propose the structure of the inclusion complex and the interaction with ctDNA. The Stern-Volmer quenching constants of the interaction of raloxifene with ctDNA in aqueous and β-CD solution are compared. The competition for binding of ctDNA with raloxifene and Methylene Blue is studied. The apparent binding constant and the number of binding sites for the binding of raloxifene with BSA in aqueous solution are significantly different from those in the presence of β-CD. The influence of β-CD on the binding of the small molecules with biological macromolecules is discussed. We infer that the binding strengths between raloxifene and macromolecules viz., ctDNA and BSA are influenced by the β-CD encapsulation. These results may suggest new ways to tune the drug binding to biomacromolecules by encapsulating specific moieties of drugs.
Journal of Molecular Recognition, Sep 8, 2014
We report in this paper that the binding of coumarin 6 (C6) to DNA can be tuned by complexing it ... more We report in this paper that the binding of coumarin 6 (C6) to DNA can be tuned by complexing it with host structures, viz. β-cyclodextrin (β-CD) and C-hexylpyrogallol-4-arene (C-HPA). Because host molecules are used as carriers of small molecules onto target sites, the exposed part of the guest molecule needs to be found out, and the relationship between the host : guest ratio and the mode of binding with the target macromolecule, that is, the DNA needs to be analyzed, in order to comprehend the preferred binding moiety and tune the binding. In this paper, the formation of the inclusion complex of C6 with β-CD and with C-HPA is studied by UV-visible, fluorescence, 2D rotating-frame nuclear Overhauser effect correlation spectroscopy and diffusion-ordered spectroscopy nuclear magnetic resonance spectra and molecular modeling. C6 forms a 1:1 complex with β-CD and a 1:2 complex with C-HPA. The studies on the protonation of C6 in the presence and the absence of the host molecules suggest that the chromone part of C6 is outside the β-CD molecule, whereas it is fully covered by C-HPA. The binding of C6 with calf thymus DNA (ctDNA) occurs through intercalation and hydrogen bonding, and the host-guest structures remain intact on binding with ctDNA. The oxygens of the C6 molecules are exposed when inside the host molecules and aid in the hydrogen bonding with DNA.
Analytical and Bioanalytical Chemistry Research, Dec 1, 2019
The objective of the paper is to determine the effect of β-cyclodextrin complexation on the inter... more The objective of the paper is to determine the effect of β-cyclodextrin complexation on the interaction of the popular drug, Atorvastatin to bovine serum albumin. Fluorescence and 2D Rotating-frame Overhauser effect spectroscopic techniques are used to determine the stoichiometry, the binding contant, and the mode of binding of Atorvastatin to β-cyclodextrin. The role of the Atorvastatin-β-cyclodextrin complexation in modulating the binding strength of the drug to the model carrier protein bovine serum albumin is studied using absorption and fluorescence spectral measurements and molecular docking. Atorvastatin shows a fluorescence enhancement on comlplex formation with β-cyclodextrin. The results of the binding of the drug to bovine serum albumin in free-and β-cyclodextrin-bound forms. The magnitude of quenching of the fluorescence of bovine serum albumin due to drug binding, an d the Fӧrster energy transfer efficiency between the protein and the drug are decreased in the presence of β-cyclodextrin. The binding constant value of the drug-protein binding in the absence and presence of β-cyclodextrin are 5.36 × 10 4 M-1 to 2.32 × 10 4 M-1 , respectively. Atorvastatin forms a 1:2 inclusion complex with cyclodextrin. The isopropyl substituent in the pyrrole ring of Atorvastatin binds to β-cyclodextrin. Cyclodextrin modulated the binding of drug to the serum albumin, i.e., the cyclodextrin complex of Atorvastatin binds to bovine serum albumin with diminished binding strength. Nevertheless, the exposed part of the drug is found to be sufficient for interaction with the same binding pocket as the free drug binds to.
Journal of Solution Chemistry, Oct 1, 2011
Curculigosides A and B, two of the phyto-constituents of the medicinal plant Curculigo orchioides... more Curculigosides A and B, two of the phyto-constituents of the medicinal plant Curculigo orchioides gatern, were isolated. The binding properties of these curculigosides with β-cyclodextrin, and their interaction with bovine serum albumin in free and β-cyclodextrincomplexed forms, were studied using fluorescence spectroscopy. The stoichiometry and binding constants of these complexes together with their binding modes are reported. Both of the curculigoside-cyclodextrin complexes are found to bind more weakly to the bovine serum albumin molecule than their free forms. The difference in the binding strengths of curculigoside A and curculigoside B with cyclodextrin makes a difference in their binding with bovine serum albumin.
Journal of inclusion phenomena and macrocyclic chemistry, Sep 30, 2014
ABSTRACT The possible structure of the host–guest complex, Coumarin 7/β-cyclodextrin and the site... more ABSTRACT The possible structure of the host–guest complex, Coumarin 7/β-cyclodextrin and the site of binding with DNA are optimized by UV–Visible absorption, fluorescence, molecular modeling and Nuclear Magnetic Resonance spectroscopy techniques. The study of the effect of acid strength on the absorption and emission of Coumarin 7 in the presence and the absence of β-cyclodextrin shows that Coumarin 7 becomes less basic in the excited state and the encapsulation by the host molecule makes it less susceptible to get protonated. Coumarin 7 is encapsulated by β-cyclodextrin, forming a 1:1 inclusion complex. It binds to DNA with a binding constant of 3.45 × 105 M−1. The role of β-cyclodextrin on the binding of Coumarin 7 with calf thymus DNA is explained. The possibility of β-cyclodextrin encapsulation to the exposed parts of Coumarin 7–calf thymus DNA complex is reported. These studies provide insight to increase the aqueous solubility and bioavailability of Coumarin 7 by the formation of an inclusion complex with β-cyclodextrin. Graphical Abstract
Applied Nanoscience, Mar 1, 2018
Magnetic nanoparticles are envisaged to overcome the impediments in the methods of targeted drug ... more Magnetic nanoparticles are envisaged to overcome the impediments in the methods of targeted drug delivery and hence cure cancer effectively. We report herein, manganese ferrite nanoparticles, coated with β-cyclodextrin-modified polyethylene glycol as a carrier for the drug, camptothecin. The particles are of the size of ~ 100 nm and they show superparamagnetic behaviour. The saturation magnetization does not get diminished on polymer coverage of the nanoparticles. The β-cyclodextrin-polyethylene glycol conjugates are characterized using NMR and mass spectrometric techniques. By coating the magnetic nanoparticles with the cyclodextrin-tethered polymer, the drug-loading capacity is enhanced and the observed release of the drug is slow and sustained. The cell viability of HEK293 and HCT15 cells is evaluated and the cytotoxicity is enhanced when the drug is loaded in the polymer-coated magnetic nanoparticles. The noncovalent-binding based and enhanced drug loading on the nanoparticles and the sustained release make the nanocarrier a promising agent for carrying the payload to the target.
Journal of Luminescence, Jun 1, 2013
ABSTRACT
Journal of Biomolecular Structure & Dynamics, Dec 8, 2014
This work deals with the synthesis of 6-methyl-3-[(4&... more This work deals with the synthesis of 6-methyl-3-[(4'-methylphenyl)imino]methyl-4H-chromen-4-one (MMPIMC), its binding to β-cyclodextrin, and the influence of the cyclodextrin complexation on the compound's binding to bovine serum albumin (BSA). The 1:2 stoichiometry for the complexation of MMPIMC with β-cyclodextrin is determined with the binding constant of 1.90 × 10(4) M(-2). The structure of host-guest complex plays a role in protein binding of MMPIMC. One- and two-dimensional NMR spectra are used to determine the mode of binding of the guest to β-cyclodextrin cavity and the structure of the inclusion complex is proposed. The binding of MMPIMC with BSA in the absence and the presence of β-cyclodextrin is studied. The binding strengths of MMPIMC-BSA (1.73 × 10(5) M(-1)) and β-cyclodextrin-complexed MMPIMC-BSA (9.0 × 10(4) M(-1)) show difference in magnitude. The Förster Resonance Energy Transfer efficiency and the proximity of the donor and acceptor molecules, are modulated by β-cyclodextrin. Molecular modeling is used to optimize the sites and mode of binding of MMPIMC with bovine serum albumin.
Colloids and Surfaces B: Biointerfaces, 2018
75 nm-sized calcium ferrite nanoparticles are prepared as drug delivery agents. 2 The β-Cyclo... more 75 nm-sized calcium ferrite nanoparticles are prepared as drug delivery agents. 2 The β-Cyclodextrin-tethered dextran-coated nanoparticles are loaded with camptothecin. Cytotoxicity on human cervical cancer cells is studied. The toxicity of the nanoparticles on brine shrimp, Artemia salina, is reduced on the polymer coating.
Chemical Papers, 2012
The interaction of 6-methoxyflavanone (6MF, 6-methoxy-2-phenyl-4H-1-benzopyran-4-one) with calf t... more The interaction of 6-methoxyflavanone (6MF, 6-methoxy-2-phenyl-4H-1-benzopyran-4-one) with calf thymus DNA (ctDNA) was investigated by absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry in the presence and absence of β-cyclodextrin (β-CD) acting as capping agent. Molecular modelling was used to optimise the study of 6MF-β-CD and 6MF-DNA interactions. Enhancement in the fluorescence intensity of 6MF was observed due to the formation of 1 : 1 complex with β-CD. In the presence and absence of DNA, 6MF showed different characteristics such as hyperchromic effect, red shift of absorption spectra and fluorescence quenching of 6MF due to binding between 6MF and ctDNA. The nature of the binding group was found to be different for the 6MF-ctDNA and 6MF-ctDNA-β-CD systems. An increase in fluorescence intensity was observed for the 6MF-ctDNA system while varying the concentration of β-CD due to encapsulation of a part of 6MF in cyclodextrin. The results are compatible with the possibility of the interaction of dihydrobenzopyran-4-one moiety of 6MF with ctDNA as well as with β-CD. Cyclic voltammetric studies confirmed the binding interaction between 6MF and ctDNA in the absence and presence of β-CD and molecular modelling explains the site of the interaction of 6MF with cyclodextrin and ctDNA.
Nucleosides, Nucleotides & Nucleic Acids
Inorganic Chemistry Communications
Asian Journal of Chemistry
The densities (ρ), speeds of sound (u), and viscosities (η) have been measured for ternary liquid... more The densities (ρ), speeds of sound (u), and viscosities (η) have been measured for ternary liquid mixtures of tetrahydrofuran in cyclohexanone with 1-hexanol and 1-octanol at 303.15-313.15 K over the entire range of mole fractions and at atmospheric pressure 0.1 MPa. These experimental data have been used to estimate the thermophysical properties of heterocyclic compounds with aliphatic alcohols at T = 303.15, 308.15 and 313.15 K. Preliminary data was used to assess the excess free volume, internal pressure and free energy of Gibbs, which were discussed in light of the molecular interaction surviving in the mixtures. Analysis of each of the two contributions, namely interaction, free volume VE showed that the contributions are positive for all systems. The variations of these parameters with the composition and the temperature were discussed with regard to the intermolecular interactions prevailing in these mixtures. These values also indicate the formation of a hydrogen bonding (C=...
International Journal of Pharmaceutics
Journal of Molecular Structure
Inorganic Chemistry Communications
Journal of Porous Materials
Journal of Cluster Science
Journal of Inclusion Phenomena and Macrocyclic Chemistry
Journal of Biological Physics, Jul 30, 2014
We report the binding of the drug raloxifene with Calf thymus DNA (ctDNA) and bovine serum albumi... more We report the binding of the drug raloxifene with Calf thymus DNA (ctDNA) and bovine serum albumin (BSA) in the presence and absence of β-cyclodextrin (β-CD) and explain the influence of β-cyclodextrin on the binding of the drug to macromolecules. UV-Vis absorption, fluorescence, proton nuclear magnetic resonance and two-dimensional rotating-frame nuclear overhauser effect spectroscopic techniques are used to study the stoichiometry and the binding strength of the complexes. Molecular modeling is used in combination with other techniques to propose the structure of the inclusion complex and the interaction with ctDNA. The Stern-Volmer quenching constants of the interaction of raloxifene with ctDNA in aqueous and β-CD solution are compared. The competition for binding of ctDNA with raloxifene and Methylene Blue is studied. The apparent binding constant and the number of binding sites for the binding of raloxifene with BSA in aqueous solution are significantly different from those in the presence of β-CD. The influence of β-CD on the binding of the small molecules with biological macromolecules is discussed. We infer that the binding strengths between raloxifene and macromolecules viz., ctDNA and BSA are influenced by the β-CD encapsulation. These results may suggest new ways to tune the drug binding to biomacromolecules by encapsulating specific moieties of drugs.
Journal of Molecular Recognition, Sep 8, 2014
We report in this paper that the binding of coumarin 6 (C6) to DNA can be tuned by complexing it ... more We report in this paper that the binding of coumarin 6 (C6) to DNA can be tuned by complexing it with host structures, viz. β-cyclodextrin (β-CD) and C-hexylpyrogallol-4-arene (C-HPA). Because host molecules are used as carriers of small molecules onto target sites, the exposed part of the guest molecule needs to be found out, and the relationship between the host : guest ratio and the mode of binding with the target macromolecule, that is, the DNA needs to be analyzed, in order to comprehend the preferred binding moiety and tune the binding. In this paper, the formation of the inclusion complex of C6 with β-CD and with C-HPA is studied by UV-visible, fluorescence, 2D rotating-frame nuclear Overhauser effect correlation spectroscopy and diffusion-ordered spectroscopy nuclear magnetic resonance spectra and molecular modeling. C6 forms a 1:1 complex with β-CD and a 1:2 complex with C-HPA. The studies on the protonation of C6 in the presence and the absence of the host molecules suggest that the chromone part of C6 is outside the β-CD molecule, whereas it is fully covered by C-HPA. The binding of C6 with calf thymus DNA (ctDNA) occurs through intercalation and hydrogen bonding, and the host-guest structures remain intact on binding with ctDNA. The oxygens of the C6 molecules are exposed when inside the host molecules and aid in the hydrogen bonding with DNA.
Analytical and Bioanalytical Chemistry Research, Dec 1, 2019
The objective of the paper is to determine the effect of β-cyclodextrin complexation on the inter... more The objective of the paper is to determine the effect of β-cyclodextrin complexation on the interaction of the popular drug, Atorvastatin to bovine serum albumin. Fluorescence and 2D Rotating-frame Overhauser effect spectroscopic techniques are used to determine the stoichiometry, the binding contant, and the mode of binding of Atorvastatin to β-cyclodextrin. The role of the Atorvastatin-β-cyclodextrin complexation in modulating the binding strength of the drug to the model carrier protein bovine serum albumin is studied using absorption and fluorescence spectral measurements and molecular docking. Atorvastatin shows a fluorescence enhancement on comlplex formation with β-cyclodextrin. The results of the binding of the drug to bovine serum albumin in free-and β-cyclodextrin-bound forms. The magnitude of quenching of the fluorescence of bovine serum albumin due to drug binding, an d the Fӧrster energy transfer efficiency between the protein and the drug are decreased in the presence of β-cyclodextrin. The binding constant value of the drug-protein binding in the absence and presence of β-cyclodextrin are 5.36 × 10 4 M-1 to 2.32 × 10 4 M-1 , respectively. Atorvastatin forms a 1:2 inclusion complex with cyclodextrin. The isopropyl substituent in the pyrrole ring of Atorvastatin binds to β-cyclodextrin. Cyclodextrin modulated the binding of drug to the serum albumin, i.e., the cyclodextrin complex of Atorvastatin binds to bovine serum albumin with diminished binding strength. Nevertheless, the exposed part of the drug is found to be sufficient for interaction with the same binding pocket as the free drug binds to.
Journal of Solution Chemistry, Oct 1, 2011
Curculigosides A and B, two of the phyto-constituents of the medicinal plant Curculigo orchioides... more Curculigosides A and B, two of the phyto-constituents of the medicinal plant Curculigo orchioides gatern, were isolated. The binding properties of these curculigosides with β-cyclodextrin, and their interaction with bovine serum albumin in free and β-cyclodextrincomplexed forms, were studied using fluorescence spectroscopy. The stoichiometry and binding constants of these complexes together with their binding modes are reported. Both of the curculigoside-cyclodextrin complexes are found to bind more weakly to the bovine serum albumin molecule than their free forms. The difference in the binding strengths of curculigoside A and curculigoside B with cyclodextrin makes a difference in their binding with bovine serum albumin.
Journal of inclusion phenomena and macrocyclic chemistry, Sep 30, 2014
ABSTRACT The possible structure of the host–guest complex, Coumarin 7/β-cyclodextrin and the site... more ABSTRACT The possible structure of the host–guest complex, Coumarin 7/β-cyclodextrin and the site of binding with DNA are optimized by UV–Visible absorption, fluorescence, molecular modeling and Nuclear Magnetic Resonance spectroscopy techniques. The study of the effect of acid strength on the absorption and emission of Coumarin 7 in the presence and the absence of β-cyclodextrin shows that Coumarin 7 becomes less basic in the excited state and the encapsulation by the host molecule makes it less susceptible to get protonated. Coumarin 7 is encapsulated by β-cyclodextrin, forming a 1:1 inclusion complex. It binds to DNA with a binding constant of 3.45 × 105 M−1. The role of β-cyclodextrin on the binding of Coumarin 7 with calf thymus DNA is explained. The possibility of β-cyclodextrin encapsulation to the exposed parts of Coumarin 7–calf thymus DNA complex is reported. These studies provide insight to increase the aqueous solubility and bioavailability of Coumarin 7 by the formation of an inclusion complex with β-cyclodextrin. Graphical Abstract
Applied Nanoscience, Mar 1, 2018
Magnetic nanoparticles are envisaged to overcome the impediments in the methods of targeted drug ... more Magnetic nanoparticles are envisaged to overcome the impediments in the methods of targeted drug delivery and hence cure cancer effectively. We report herein, manganese ferrite nanoparticles, coated with β-cyclodextrin-modified polyethylene glycol as a carrier for the drug, camptothecin. The particles are of the size of ~ 100 nm and they show superparamagnetic behaviour. The saturation magnetization does not get diminished on polymer coverage of the nanoparticles. The β-cyclodextrin-polyethylene glycol conjugates are characterized using NMR and mass spectrometric techniques. By coating the magnetic nanoparticles with the cyclodextrin-tethered polymer, the drug-loading capacity is enhanced and the observed release of the drug is slow and sustained. The cell viability of HEK293 and HCT15 cells is evaluated and the cytotoxicity is enhanced when the drug is loaded in the polymer-coated magnetic nanoparticles. The noncovalent-binding based and enhanced drug loading on the nanoparticles and the sustained release make the nanocarrier a promising agent for carrying the payload to the target.
Journal of Luminescence, Jun 1, 2013
ABSTRACT
Journal of Biomolecular Structure & Dynamics, Dec 8, 2014
This work deals with the synthesis of 6-methyl-3-[(4&... more This work deals with the synthesis of 6-methyl-3-[(4'-methylphenyl)imino]methyl-4H-chromen-4-one (MMPIMC), its binding to β-cyclodextrin, and the influence of the cyclodextrin complexation on the compound's binding to bovine serum albumin (BSA). The 1:2 stoichiometry for the complexation of MMPIMC with β-cyclodextrin is determined with the binding constant of 1.90 × 10(4) M(-2). The structure of host-guest complex plays a role in protein binding of MMPIMC. One- and two-dimensional NMR spectra are used to determine the mode of binding of the guest to β-cyclodextrin cavity and the structure of the inclusion complex is proposed. The binding of MMPIMC with BSA in the absence and the presence of β-cyclodextrin is studied. The binding strengths of MMPIMC-BSA (1.73 × 10(5) M(-1)) and β-cyclodextrin-complexed MMPIMC-BSA (9.0 × 10(4) M(-1)) show difference in magnitude. The Förster Resonance Energy Transfer efficiency and the proximity of the donor and acceptor molecules, are modulated by β-cyclodextrin. Molecular modeling is used to optimize the sites and mode of binding of MMPIMC with bovine serum albumin.
Colloids and Surfaces B: Biointerfaces, 2018
75 nm-sized calcium ferrite nanoparticles are prepared as drug delivery agents. 2 The β-Cyclo... more 75 nm-sized calcium ferrite nanoparticles are prepared as drug delivery agents. 2 The β-Cyclodextrin-tethered dextran-coated nanoparticles are loaded with camptothecin. Cytotoxicity on human cervical cancer cells is studied. The toxicity of the nanoparticles on brine shrimp, Artemia salina, is reduced on the polymer coating.
Chemical Papers, 2012
The interaction of 6-methoxyflavanone (6MF, 6-methoxy-2-phenyl-4H-1-benzopyran-4-one) with calf t... more The interaction of 6-methoxyflavanone (6MF, 6-methoxy-2-phenyl-4H-1-benzopyran-4-one) with calf thymus DNA (ctDNA) was investigated by absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry in the presence and absence of β-cyclodextrin (β-CD) acting as capping agent. Molecular modelling was used to optimise the study of 6MF-β-CD and 6MF-DNA interactions. Enhancement in the fluorescence intensity of 6MF was observed due to the formation of 1 : 1 complex with β-CD. In the presence and absence of DNA, 6MF showed different characteristics such as hyperchromic effect, red shift of absorption spectra and fluorescence quenching of 6MF due to binding between 6MF and ctDNA. The nature of the binding group was found to be different for the 6MF-ctDNA and 6MF-ctDNA-β-CD systems. An increase in fluorescence intensity was observed for the 6MF-ctDNA system while varying the concentration of β-CD due to encapsulation of a part of 6MF in cyclodextrin. The results are compatible with the possibility of the interaction of dihydrobenzopyran-4-one moiety of 6MF with ctDNA as well as with β-CD. Cyclic voltammetric studies confirmed the binding interaction between 6MF and ctDNA in the absence and presence of β-CD and molecular modelling explains the site of the interaction of 6MF with cyclodextrin and ctDNA.
Nucleosides, Nucleotides & Nucleic Acids
Inorganic Chemistry Communications
Asian Journal of Chemistry
The densities (ρ), speeds of sound (u), and viscosities (η) have been measured for ternary liquid... more The densities (ρ), speeds of sound (u), and viscosities (η) have been measured for ternary liquid mixtures of tetrahydrofuran in cyclohexanone with 1-hexanol and 1-octanol at 303.15-313.15 K over the entire range of mole fractions and at atmospheric pressure 0.1 MPa. These experimental data have been used to estimate the thermophysical properties of heterocyclic compounds with aliphatic alcohols at T = 303.15, 308.15 and 313.15 K. Preliminary data was used to assess the excess free volume, internal pressure and free energy of Gibbs, which were discussed in light of the molecular interaction surviving in the mixtures. Analysis of each of the two contributions, namely interaction, free volume VE showed that the contributions are positive for all systems. The variations of these parameters with the composition and the temperature were discussed with regard to the intermolecular interactions prevailing in these mixtures. These values also indicate the formation of a hydrogen bonding (C=...
International Journal of Pharmaceutics
Journal of Molecular Structure
Inorganic Chemistry Communications
Journal of Porous Materials
Journal of Cluster Science