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Gopinatha Suresh Kumar - One of the best experts on this subject based on the ideXlab platform.
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interaction of Proflavine with the rna polynucleotide polyriboadenylic acid polyribouridylic acid photophysical and calorimetric studies
Journal of Biomolecular Structure & Dynamics, 2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:The binding of Proflavine, an acriflavine derivative, with the RNA polynucletodide polyadenylic acid–polyuridylic acid is investigated here to understand the structural and thermodynamic basis of t...
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a calorimetric characterization of the interaction of quinacrine with poly i poly c and its comparison to Proflavine
The Journal of Chemical Thermodynamics, 2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Abstract Thermodynamics of the interaction of quinacrine with poly(I).poly(C) was studied in comparison to Proflavine using microcalorimetry. Isothermal titration calorimetry results suggested that the binding of quinacrine to poly(I).poly(C) was enthalpy dominated with a smaller but favourable entropic contribution at 298.15 K. For Proflavine, the binding was predominantly entropy dominated at 298.15 K. The equilibrium constant for quinacrine-poly(I).poly(C) complexation was calculated to be (5.11 ± 0.88)·105 M−1 while for Proflavine the equilibrium constant was (3.45 ± 0.85)·105 M−1 at 298.15 K. With increasing temperature the equilibrium constant decreased, the standard molar enthalpic contribution increased in magnitude, the positive standard molar entropic contribution decreased while standard molar Gibbs energy remained almost invariant for both the systems. An enthalpy-entropy compensation phenomenon was observed for the complexation of both quinacrine and Proflavine with poly(I).poly(C). Negative standard molar heat capacity values were also observed for the complexation of both quinacrine and Proflavine with poly(I).poly(C) which suggested the involvement of hydrophobic forces in the binding reaction. Salt dependent calorimetric data and the dissection of the standard molar Gibbs energy suggested the involvement of a dominant non-electrostatic component in the binding reaction for both quinacrine and Proflavine.
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Interaction of Proflavine with the RNA polynucleotide polyriboadenylic acid–polyribouridylic acid: photophysical and calorimetric studies
2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:The binding of Proflavine, an acriflavine derivative, with the RNA polynucletodide polyadenylic acid–polyuridylic acid is investigated here to understand the structural and thermodynamic basis of the binding process. Such binding data are crucial for designing viable theraperutic agents. Spectroscopic studies clearly suggest a strong binding interaction between Proflavine and polyadenylic acid–polyuridylic acid leading to efficient energy transfer between the poly AU base pairs and Proflavine. The stoichiometry of Proflavine polyadenylic acid–polyuridylic acid binding was independently estimated by continuous variation analysis of Job. An intercalative binding model is envisaged for the binding from hydrodynamic studies. Circular dichroism experiments revealed that the binding induced conformational changes in the RNA, and also led to induction of optical activity in the bound dye molecules. The binding affinity of the complex was deduced to be (6.57 ± 0.75) 105 M−1 at (298.15 ± 0.10) K from isothermal titration calorimetry experiment. Positive entropy and negative enthalpy changes characterized the complexation. The binding was observed to be weaker both at higher temperatures and increased [Na+]. The affinity of binding decreased with increasing [Na+]. When the Gibbs energy was parsed between polyelectrolytic and nonpolyelectropytic components, it surprisingly revealed a higher role for the non-polyelectrolytic forces. These results present new data for developing RNA targeted ligands. Communicated by Ramaswamy H. Sarma
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a biophysical investigation on the binding of Proflavine with human hemoglobin insights from spectroscopy thermodynamics and afm studies
Journal of Photochemistry and Photobiology B-biology, 2016Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Interaction of Proflavine with hemoglobin (Hgb) was studied employing spectroscopy, calorimetry, and atomic force microscopy. The equilibrium constant was found to be of the order 104M-1. The quenching of Hgb fluorescence by Proflavine was due to the complex formation. Calculation of the molecular distance (r) between the donor (β-Trp37 of Hgb) and acceptor (Proflavine) suggested that energy can be efficiently transferred from the β-Trp37 residue at the α1β2 interface of the protein to the dye. Proflavine induced significant secondary structural changes in Hgb. Synchronous fluorescence studies showed that Proflavine altered the microenvironment around the tryptophan residues to a greater extent than the tyrosine residues. Circular dichroism spectral studies showed that Proflavine caused significant reduction in the α-helical content of Hgb. The esterase activity assay further complemented the circular dichroism data. The Soret band intensity of Hgb decreased upon complexation. Differential scanning calorimetry and circular dichroism melting results revealed that Proflavine induced destabilization of Hgb. The binding was driven by both positive entropy and negative enthalpy. Atomic force microscopy studies revealed that the essential morphological features of hemoglobin were retained in the presence of Proflavine. Overall, insights on the photophysical aspects and energetics of the binding of Proflavine with Hgb are presented.
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calorimetric investigation on the interaction of Proflavine with human telomeric g quadruplex dna
The Journal of Chemical Thermodynamics, 2016Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Abstract The interaction of an acridine dye, Proflavine, with human telomeric G-quadruplex DNA was characterized by isothermal titration calorimetry and differential scanning calorimetry. The equilibrium constant of binding was deduced to be (1.36 ± 0.09) · 10 6 M −1 at T = 298.15 K. The binding reaction was driven by both negative enthalpy and positive entropy contributions. The equilibrium constant decreased and the reaction became increasingly enthalpy driven with rise in temperature. However, the standard molar Gibbs energy change exhibited only marginal alterations suggesting the occurrence of enthalpy–entropy compensation. Negative heat capacity values were also obtained from the temperature dependence of enthalpy change. Parsing of the standard molar Gibbs energy using the salt dependent calorimetric data revealed that the binding was dominated by non-polyelectrolytic forces which remained virtually unaltered with changing salt concentration. Proflavine binding also significantly enhanced the thermal stability of G-quadruplex DNA against thermal unfolding.
Anirban Basu - One of the best experts on this subject based on the ideXlab platform.
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interaction of Proflavine with the rna polynucleotide polyriboadenylic acid polyribouridylic acid photophysical and calorimetric studies
Journal of Biomolecular Structure & Dynamics, 2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:The binding of Proflavine, an acriflavine derivative, with the RNA polynucletodide polyadenylic acid–polyuridylic acid is investigated here to understand the structural and thermodynamic basis of t...
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a calorimetric characterization of the interaction of quinacrine with poly i poly c and its comparison to Proflavine
The Journal of Chemical Thermodynamics, 2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Abstract Thermodynamics of the interaction of quinacrine with poly(I).poly(C) was studied in comparison to Proflavine using microcalorimetry. Isothermal titration calorimetry results suggested that the binding of quinacrine to poly(I).poly(C) was enthalpy dominated with a smaller but favourable entropic contribution at 298.15 K. For Proflavine, the binding was predominantly entropy dominated at 298.15 K. The equilibrium constant for quinacrine-poly(I).poly(C) complexation was calculated to be (5.11 ± 0.88)·105 M−1 while for Proflavine the equilibrium constant was (3.45 ± 0.85)·105 M−1 at 298.15 K. With increasing temperature the equilibrium constant decreased, the standard molar enthalpic contribution increased in magnitude, the positive standard molar entropic contribution decreased while standard molar Gibbs energy remained almost invariant for both the systems. An enthalpy-entropy compensation phenomenon was observed for the complexation of both quinacrine and Proflavine with poly(I).poly(C). Negative standard molar heat capacity values were also observed for the complexation of both quinacrine and Proflavine with poly(I).poly(C) which suggested the involvement of hydrophobic forces in the binding reaction. Salt dependent calorimetric data and the dissection of the standard molar Gibbs energy suggested the involvement of a dominant non-electrostatic component in the binding reaction for both quinacrine and Proflavine.
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Interaction of Proflavine with the RNA polynucleotide polyriboadenylic acid–polyribouridylic acid: photophysical and calorimetric studies
2019Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:The binding of Proflavine, an acriflavine derivative, with the RNA polynucletodide polyadenylic acid–polyuridylic acid is investigated here to understand the structural and thermodynamic basis of the binding process. Such binding data are crucial for designing viable theraperutic agents. Spectroscopic studies clearly suggest a strong binding interaction between Proflavine and polyadenylic acid–polyuridylic acid leading to efficient energy transfer between the poly AU base pairs and Proflavine. The stoichiometry of Proflavine polyadenylic acid–polyuridylic acid binding was independently estimated by continuous variation analysis of Job. An intercalative binding model is envisaged for the binding from hydrodynamic studies. Circular dichroism experiments revealed that the binding induced conformational changes in the RNA, and also led to induction of optical activity in the bound dye molecules. The binding affinity of the complex was deduced to be (6.57 ± 0.75) 105 M−1 at (298.15 ± 0.10) K from isothermal titration calorimetry experiment. Positive entropy and negative enthalpy changes characterized the complexation. The binding was observed to be weaker both at higher temperatures and increased [Na+]. The affinity of binding decreased with increasing [Na+]. When the Gibbs energy was parsed between polyelectrolytic and nonpolyelectropytic components, it surprisingly revealed a higher role for the non-polyelectrolytic forces. These results present new data for developing RNA targeted ligands. Communicated by Ramaswamy H. Sarma
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a biophysical investigation on the binding of Proflavine with human hemoglobin insights from spectroscopy thermodynamics and afm studies
Journal of Photochemistry and Photobiology B-biology, 2016Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Interaction of Proflavine with hemoglobin (Hgb) was studied employing spectroscopy, calorimetry, and atomic force microscopy. The equilibrium constant was found to be of the order 104M-1. The quenching of Hgb fluorescence by Proflavine was due to the complex formation. Calculation of the molecular distance (r) between the donor (β-Trp37 of Hgb) and acceptor (Proflavine) suggested that energy can be efficiently transferred from the β-Trp37 residue at the α1β2 interface of the protein to the dye. Proflavine induced significant secondary structural changes in Hgb. Synchronous fluorescence studies showed that Proflavine altered the microenvironment around the tryptophan residues to a greater extent than the tyrosine residues. Circular dichroism spectral studies showed that Proflavine caused significant reduction in the α-helical content of Hgb. The esterase activity assay further complemented the circular dichroism data. The Soret band intensity of Hgb decreased upon complexation. Differential scanning calorimetry and circular dichroism melting results revealed that Proflavine induced destabilization of Hgb. The binding was driven by both positive entropy and negative enthalpy. Atomic force microscopy studies revealed that the essential morphological features of hemoglobin were retained in the presence of Proflavine. Overall, insights on the photophysical aspects and energetics of the binding of Proflavine with Hgb are presented.
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calorimetric investigation on the interaction of Proflavine with human telomeric g quadruplex dna
The Journal of Chemical Thermodynamics, 2016Co-Authors: Anirban Basu, Gopinatha Suresh KumarAbstract:Abstract The interaction of an acridine dye, Proflavine, with human telomeric G-quadruplex DNA was characterized by isothermal titration calorimetry and differential scanning calorimetry. The equilibrium constant of binding was deduced to be (1.36 ± 0.09) · 10 6 M −1 at T = 298.15 K. The binding reaction was driven by both negative enthalpy and positive entropy contributions. The equilibrium constant decreased and the reaction became increasingly enthalpy driven with rise in temperature. However, the standard molar Gibbs energy change exhibited only marginal alterations suggesting the occurrence of enthalpy–entropy compensation. Negative heat capacity values were also obtained from the temperature dependence of enthalpy change. Parsing of the standard molar Gibbs energy using the salt dependent calorimetric data revealed that the binding was dominated by non-polyelectrolytic forces which remained virtually unaltered with changing salt concentration. Proflavine binding also significantly enhanced the thermal stability of G-quadruplex DNA against thermal unfolding.
Marcella Venturini - One of the best experts on this subject based on the ideXlab platform.
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change of the binding mode of the dna Proflavine system induced by ethanol
Journal of Physical Chemistry B, 2010Co-Authors: Begona Garcia, Fernando Secco, Jose M Leal, R Ruiz, Tarita Biver, Marcella VenturiniAbstract:The equilibria and kinetics of the binding of Proflavine to poly(dG-dC)·poly(dG-dC) and poly(dA-dT)·poly(dA-dT) were investigated in ethanol/water mixtures using spectrophotometric, circular dichroism, viscometric, and T-jump methods. All methods concur in showing that two modes of interaction are operative: intercalation and surface binding. The latter mode is favored by increasing ethanol and/or the Proflavine content. Both static and kinetic experiments show that, concerning the poly(dG-dC)·poly(dG-dC)/Proflavine system, intercalation largely prevails up to 20% EtOH. For higher EtOH levels surface binding becomes dominant. Concerning the poly(dA-dT)·poly(dA-dT)/Proflavine system, melting experiments show that addition of Proflavine stabilizes the double stranded structure, but the effect is reduced in the presence of EtOH. The ΔH° and ΔS° values of the melting process, measured at different concentrations of added Proflavine, are linearly correlated, revealing the presence of the enthalpy−entropy compe...
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relaxation kinetics of the interaction between rna and metal intercalators the poly a poly u platinum Proflavine system
Archives of Biochemistry and Biophysics, 2005Co-Authors: Tarita Biver, Fernando Secco, Marcella VenturiniAbstract:Abstract The interactions of Poly(A)·Poly(U) with the cis-platinum derivative of Proflavine [{PtCl(tmen)}2{HNC13H7(NHCH2CH2)2}]+ (PRPt) and Proflavine (PR) are investigated by spectrophotometry, spectrofluorimetry and T-jump relaxation at I = 0.2 M, pH 7.0, and T = 25 °C. Base–dye interactions prevail at high RNA/dye ratio and binding isotherms analysis reveals that both dyes bind to Poly(A)·Poly(U) according to the excluded site model (n = 2). Only one relaxation effect is observed for the Poly(A)·Poly(U)/PRPt system, whereas two effects are observed with Poly(A)·Poly(U)/PR. The results agree with the sequence D + S ⇆ D, S ⇆ DSI ⇆ DSII, where D,S is an external complex, DSI is a partially intercalated species, and DSII is the fully intercalated complex. Formation of DSII could be observed in the case of Proflavine only. This result is interpreted by assuming that the platinum-containing residue of PRPt hinders the full intercalation of the acridine residue.
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Intercalation of Proflavine and a Platinum Derivative of Proflavine into Double-Helical Poly(A)
Biophysical journal, 1999Co-Authors: Carlo Ciatto, M. L. D'amico, Giovanni Natile, Fernando Secco, Marcella VenturiniAbstract:Abstract The equilibria and kinetics of the interactions of Proflavine (PR) and its platinum-containing derivative [{PtCl(tmen)} 2 {HNC 13 H 7 (NHCH 2 CH 2 ) 2 }] + (PRPt) with double-stranded poly(A) have been investigated by spectrophotometry and Joule temperature-jump relaxation at ionic strength 0.1M, 25°C, and pH 5.2. Spectrophotometric measurements indicate that base-dye interactions are prevailing. T-jump experiments with polarized light showed that effects due to field-induced alignment could be neglected. Both of the investigated systems display two relaxation effects. The kinetic features of the reaction are discussed in terms of a two-step series mechanism in which a precursor complex DS I is formed in the fast step, which is then converted to a final complex in the slow step. The rate constants of the fast step are k 1 =(2.5±0.4)×10 6 M −1 s −1 , k −1 =(2.4±0.1)×10 3 s −1 for poly(A)-PR and k 1 =(2.3±0.1)×10 6 M −1 s −1 , k −1 =(1.6±0.2)×10 3 s −1 for poly(A)-PRPt. The rate constants for the slow step are k 2 =(4.5±0.5)×10 2 s −1 , k −2 =(1.7±0.1)×10 2 s −1 for poly(A)-PR and k 2 =9.7±1.2s −1 , k −2 =10.6±0.2s −1 for poly(A)-PRPt. Spectrophotometric measurements yield for the equilibrium constants and site size the values K =(4.5±0.1)×10 3 M −1 , n =1.3±0.5 for poly(A)-PR and K =(2.9±0.1)×10 3 M −1 , n =2.3±0.6 for poly(A)-PRPt. The values of k 1 are similar and lower than expected for diffusion-limited reactions. The values of k −1 are similar as well. It is suggested that the formation of DS I involves only the Proflavine residues in both systems. In contrast, the values of k 2 and k −2 in poly(A)-PRPt are much lower than in poly(A)-PR. The results suggest that in the complex DS II of poly(A)-PRPt both Proflavine and platinum residues are intercalated. In addition, a very slow process was detected and ascribed to the covalent binding of Pt(II) to the adenine.
P Natarajan - One of the best experts on this subject based on the ideXlab platform.
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photoprocesses of molecules encapsulated in porous solids xi excited state dynamics of Proflavine and photosensitization of tio2 in nanoporous materials
Microporous and Mesoporous Materials, 2014Co-Authors: Karuppannan Senthilkumar, Singaravelu Chandra Mohan, Shanmugam Easwaramoorthi, Kandasamy Jothivenkatachalam, P NatarajanAbstract:Abstract Photosensitization of titanium dioxide (TiO2) encapsulated in the nanoporous materials of different pore size using Proflavine dye as the sensitizer was studied using steady state and time resolved fluorescence spectral techniques. The titanium dioxide encapsulated nanoporous materials was prepared by ion exchange method and were characterized by UV–visible diffuse reflectance spectra, ICP-OES, BET and powder XRD techniques. The observed results show that TiO2 were encapsulated in the nanochannels and nanocavities of the host materials. The photophysical properties of Proflavine are found to be influenced by the pore size and the Si/Al ratio of the host materials. Photosensitization of TiO2 in the host by Proflavine was inferred from the decreased stead state fluorescence intensity of the dye molecule. In the case of the dye encapsulated TiO2 loaded ZSM-5, fluorescence intensity decreases with red shifted emission maximum. Excitation of Proflavine in presence of TiO2 nanoparticles leads to protonation of Proflavine in the excited state as confirmed in ultrafast time resolved fluorescence and decay associated spectral studies. On the other hand, no protonated Proflavine was detected when zeolite-Y and MCM-41 were used as the host material.
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existence of a new emitting singlet state of Proflavine femtosecond dynamics of the excited state processes and quantum chemical studies in different solvents
Journal of Physical Chemistry A, 2012Co-Authors: Karuppannan Senthil Kumar, Chellappan Selvaraju, Ezekiel Padma J Malar, P NatarajanAbstract:Proflavine (3,6-diaminoacridine) shows fluorescence emission with lifetime, 4.6 ± 0.2 ns, in all the solvents irrespective of the solvent polarity. To understand this unusual photophysical property, investigations were carried out using steady state and time-resolved fluorescence spectroscopy in the pico- and femtosecond time domain. Molecular geometries in the ground and low-lying excited states of Proflavine were examined by complete structural optimization using ab initio quantum chemical computations at HF/6-311++G** and CIS/6-311++G** levels. Time dependent density functional theory (TDDFT) calculations were performed to study the excitation energies in the low-lying excited states. The steady state absorption and emission spectral details of Proflavine are found to be influenced by solvents. The femtosecond fluorescence decay of the Proflavine in all the solvents follows triexponential function with two ultrafast decay components (τ1 and τ2) in addition to the nanosecond component. The ultrafast dec...
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novel excited state proton transfer reaction observed for Proflavine encapsulated in the channels of modified mcm 41
Microporous and Mesoporous Materials, 2007Co-Authors: K Ananthanarayanan, Chellappan Selvaraju, P NatarajanAbstract:Proflavine (3,6-diamino acridine) was encapsulated in mesoporous MCM-41 and in a silane modified MCM-41. Synthesised MCM-41 and modified MCM-41 materials were characterised by XRD, BET, and FT-IR methods. In the dye-encapsulated mesoporous materials the interactions between encapsulated Proflavine and the internal surfaces of the porous materials are found to modify the optical spectra and the excited state dynamics of the confined Proflavine molecules. In MCM-41 as evidenced by the absorption and emission spectra, Proflavine exists in the monocationic form (PFH + ) with a characteristic absorption maximum at 444 nm. In the silane modified MCM-41, Proflavine is found to be present in the neutral form with the characteristic absorption maximum at 394 nm. Steady state fluorescence spectra for all the dye-encapsulated mesoporous materials and lifetimes of the excited state of Proflavine encapsulated in these hosts were investigated. Excited state proton transfer reaction is observed for the dye lodged in the nanometer-sized pores of the silane modified MCM-41. A delayed emission in the picosecond time resolved emission decay measurements of the excited state of the dye confirms this process.
Martine Demeunynck - One of the best experts on this subject based on the ideXlab platform.
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Proflavine derivatives as fluorescent imaging agents of amyloid deposits
Bioorganic & Medicinal Chemistry Letters, 2011Co-Authors: Dominique Garin, Fatima Oukhatar, Andrew B Mahon, Andrew C Try, Michel Duboisdauphin, Frank M Laferla, Martine Demeunynck, M Sallanon, Sabine ChiericiAbstract:Abstract A series of Proflavine derivatives for use to further image Aβ amyloid deposits were synthesized and characterized. Aged 3xTg-AD (23 months old) mice hippocampus sections incubated with these derivatives revealed preferential labeling of amyloid plaques. Furthermore an in vitro binding study showed an inhibitory effect, although moderate, of these compounds on Aβ 40 fibril formation. This study highlights the potential of Proflavine as a molecular scaffold for designing new Aβ imaging agents, its native fluorescence allowing in vitro neuropathological staining in AD damaged brain sections.
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synthesis and dna interaction of a mixed Proflavine phenanthroline troger base
European Journal of Medicinal Chemistry, 2002Co-Authors: Brigitte Baldeyrou, Christian Bailly, Christelle Tardy, Pierre Colson, Claude Houssier, Franck Charmantray, Martine DemeunynckAbstract:We report the synthesis of an asymmetric Troger base containing the two well characterised DNA binding chromophores, Proflavine and phenanthroline. The mode of interaction of the hybrid molecule was investigated by circular and linear dichroism experiments and a biochemical assay using DNA topoisomerase I. The data are compatible with a model in which the Proflavine moiety intercalates between DNA base pairs and the phenanthroline ring occupies the DNA groove. DNase I cleavage experiments were carried out to investigate the sequence preference of the hybrid ligand and a well resolved footprint was detected at a site encompassing two adjacent 5'-GTC.5-GAC triplets. The sequence preference of the asymmetric molecule is compared to that of the symmetric analogues.
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enantiospecific recognition of dna sequences by a Proflavine troger base
Biochemical and Biophysical Research Communications, 2000Co-Authors: Christian Bailly, Martine Demeunynck, William Laine, Jean LhommeAbstract:Abstract The DNA interaction of a chiral Troger base derived from Proflavine was investigated by DNA melting temperature measurements and complementary biochemical assays. DNase I footprinting experiments demonstrate that the binding of the Proflavine-based Troger base is both enantio- and sequence-specific. The (+)-isomer poorly interacts with DNA in a non-sequence-selective fashion. In sharp contrast, the corresponding (−)-isomer recognizes preferentially certain DNA sequences containing both A · T and G · C base pairs, such as the motifs 5′-GTT · AAC and 5′-ATGA · TCAT. This is the first experimental demonstration that acridine-type Troger bases can be used for enantiospecific recognition of DNA sequences.