DNA Binding Potency Research Articles

Structural investigations of new tridentate-phenylacetohydrazide Schiff base metal chelates: X-ray diffraction, Hirshfeld surface analyses, DFT, antibacterial and molecular docking studies

The coordination complexes of a tridentate-phenylacetohydrazide Schiff base (2-hydroxybenzylidene-2-phenylacetohydrazide, HL) with metal ions, namely, iron(II), zinc(II), palladium (II), silver(I) and cadmium(II), were synthesized and investigated using various analytical and spectroscopic techniques. A single-crystal X-ray diffraction analysis was performed on the silver derivative. The HL ligand and Ag complex were also characterized via Hirshfeld surface analyses. Both X-ray and Hirshfeld surface analysis revealed intriguing structure and geometric characteristics, as well as remarkably intramolecular and intermolecular hydrogen bonding. All metal ions, with the exception of palladium one, bonded to two molecules of ligand without deprotonation of the hydroxyl moieties. In addition, 1H NMR studies of the diamagnetic complexes and X-ray analysis of the silver complex revealed the presence of the unprotonated OH. DFT-B3LYP calculations were used to determine the energy-minimized molecular geometric arrangements of the Pd(II), Ag(I), and Cd(II) derivatives. Quantum global reactivities of the complexes were also computed. Antibacterial and molecular docking studies of complexes were carried out to examine the potential applications of derivatives as therapeutic reagents. The Ag(I) complex showed the highest antibacterial inhibition towards the tested bacteria with zone diameter = 21.7, 21.0, 19.3 and 15.7 mm. Molecular docking analysis revealed that the complexes have high binding affinities against the selected receptors (PDB: 1BNA and 5AEP) and demonstrated different DNA binding potencies.

Synthesis, crystal structure elucidation, DNA-binding and micellization behavior of copper(II) carboxylate complexes

Three new oxygen bridged binuclear and mononuclear copper(II) complexes having general formulae [L2Cu(2,2′-bipyridine)2CuL2] (A), [L′2Cu(2,2′-bipyridine)H2O] (B), [L″2Cu(2,2′-bipyridine)2CuL″2] (C) where L = ortho-nitrophenyl acetate, L′ = para-methoxyphenyl acetate and L″ = para-bromophenyl acetate have been prepared and characterized spectroscopically as well as structurally. The geometry around each Cu(II) ion was found square pyramidal in all the complexes. FT-IR data of the complexes were in agreement with that of the single crystal XRD. Electronic absorption spectra indicated broad absorption bands with λmax = 671, 715 and 700 nm typical of Cu2+ with 2B1g as ground state in A-C, respectively. Crystalline nature of the complexes was ascertained from its powder XRD spectra which showed several peaks in 2θ range 5–30. Electrochemistry yielded two redox pairs conforming to irreversible Cu(III)/Cu(II) and Cu(II)/Cu(I) processes typical of complexes with Cu2+ redox centers. Complex-surfactant interactions were studied via conductometry and absorption spectrophotometry. DNA binding abilities of complexes A-C were studied via absorption spectrophotometry, cyclic voltammetry, spectrofluorometry and viscosity measurement. The former three techniques yielded excellent intrinsic binding constant values for complexes. The excellent DNA-binding potency heralds the biological importance of the synthesized complexes.

New transition metal complexes of 1‐phenyl‐2‐((quinolin‐2‐ylmethylene)amino)ethan‐1‐ol Schiff base: Spectroscopic, X‐ray, DFT, Hirshfeld surface analysis, biological, and molecular docking studies

A novel Schiff base ligand (HL), derived from the condensation of phenylethanolamine and quinoline‐2‐carboxaldehyde, and its coordination complexes with some transition metal ions, Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pd(II), were synthesized. The reported new compounds were characterized using different analytical and spectroscopic techniques. The structure ofHLand its cobalt complex was also solved by conventional X‐ray diffraction technique. Hirshfeld surface analysis of the ligand and cobalt complexes was investigated. Interesting structural features with unique hydrogen bonding formation were observed. Molecular geometries ofHLand the reported complexes were investigated using the DFT‐B3LYP level of theory. The quantum global reactivity descriptors were also calculated. Biological screening and molecular docking studies of the ligand and complexes are reported to explore their potential application as therapeutic drugs. The biological studies and molecular docking were correlated to each other and with the quantum reactivity descriptors. The studies supported that the complexes could bind to DNA via intercalative mode and showed various DNA binding potency.

Abstract P2-13-33: Preclinical development of DHES0815A: A HER2-directed antibody-drug conjugate comprised of a reduced potency PBD dimer linked to a domain I binding HER2 antibody

Abstract Background: Many HER2-directed antibody-drug conjugates (ADCs) in early development employ trastuzumab linked to tubulin binding agents as the cytotoxic drug. DHES0815A is an ADC consisting of a THIOMABTM humanized IgG1 anti-HER2 monoclonal antibody (hu7C2), which binds domain 1 of the HER2 ECD, conjugated via a disulfide linker to PBD-monoamide (MA), a DNA mono-alkylating agent. The reduced potency of the PBD-MA payload compared to PBD dimers and the stability of the conjugation site and linker were designed to improve tolerability, whereas the binding of hu7C2 to a HER2 epitope distinct from trastuzumab and pertuzumab allows combination with existing HER2 therapies. . Methods: Modifications at one imine in the PBD (pyrrolobenzodiazepine) dimer produced mono-alkylating PBDs that were assessed for DNA binding, permeability and cell potency. Each modified PBD was conjugated to hu7C2 LC K149C via a disulfide linker and assessed in HER2-positive models in vitro and in vivo. Safety studies were performed in female and male cynomolgus monkey treated every 3 weeks X 5, with a 7-week follow-up. Assessments included hematology, clinical chemistry, anti-drug antibody, standard clinical, neurological and ophthalmic exams and histopathology. Results: Our goal was design of a reduced potency PBD dimer ADC to achieve dosing in the linear PK range for optimal exposure, efficacy and safety. PBD dimers contain 2 reactive imines that bis-alkylate and crosslink DNA. Mono-alkylating PBD dimers were assessed in DNA binding, potency and permeability assays to select the optimal mono-alkylator, PBD-MA, for further investigation. hu7C2-disulfide-PBD-MA, or DHES0815A, was potent across HER2-positive breast and gastric cancer models in vitro and in vivo, with little effect on HER2-negative tumors or normal primary cells in vitro. DHES0815A was more potent than T-DM1 in HER2-positive and HER2-low breast and gastric cancer PDX models and demonstrated combination activity with standard of care agents T-DM1 or docetaxel. Mechanistically, treatment of HER2-positive cells with DHES0815A resulted in late S-phase cell cycle arrest; induction of DNA damage markers γH2AX, phospho-p53, phospho-CHK2, induction of apoptosis, and bystander activity. Pharmacokinetic analysis showed dose-proportional PK, with linear biphasic PK >/= 4mg/kg in cynomolgus monkey. Safety studies in cynomolgus monkey treated with 4, 8 or 12 mg/kg demonstrated that findings were non-adverse, monitorable and manageable. All doses were tolerated with few clinical observations and minimal to mild clinical pathology changes. Target organs were skin, bone marrow, lung and eye. The HNSTD (highest non-severely toxic dose) was 12 mg/kg. This dose enabled a starting dose of 0.6 mg/kg for phase 1 testing. Conclusions: DHES0815A is a HER2-directed ADC comprised of a domain I binding antibody linked to a reduced potency PBD dimer, PBD-MA, via a reducible disulfide linker. The antibody does not interfere with trastuzumab or pertuzumab binding, allowing combination with existing HER2 therapies. The reduced potency payload allows dosing in the linear PK range, supporting our hypothesis. DHES0815A demonstrated dose-dependent anti-tumor efficacy in multiple HER2+ breast and gastric cancer models, and showed efficacy in HER2-low models, where T-DM1 was inactive. Enhanced anti-tumor activity was observed combining DHES0815A with T-DM1, trastuzumab/pertuzumab or docetaxel. Studies in cynomolgus monkey demonstrated a safety profile compatible with initiating a phase 1 clinical trial. The phase 1 data will be presented in a separate presentation. Citation Format: Gail Lewis Phillips, Guangmin Li, Jun Guo, Shang-Fan Yu, Genee Lee, Donglu Zhang, Peter Dragovich, Thomas Pillow, Binqing Wei, M. Violet Lee, Ola Saad, Shab Masih, Douglas Leipold, Lisa Crocker, Melissa Schutten. Preclinical development of DHES0815A: A HER2-directed antibody-drug conjugate comprised of a reduced potency PBD dimer linked to a domain I binding HER2 antibody [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-13-33.

Synthesis, spectroscopic, DFT calculations, biological activities and molecular docking studies of new isoxazolone, pyrazolone, triazine, triazole and amide derivatives

Ethyl-2-cyano-2-(2-(3-nitrophenyl)hydrazono)acetate was synthesized and used as a versatile reagent for the synthesis of different heterocyclic compounds such as isoxazolone, pyrazolone, triazine, triazole and amide derivatives via its reactions with different nucleophiles. Conventional, microwave and grinding techniques were used for synthesis of the newly isolated derivatives. Various physical parameters were calculated from the percentage yield and reaction time in order to compare between the three techniques. The reported compounds were characterized by elemental analyses and different spectroscopic tools such as IR, 1H NMR, 13C NMR and mass spectrometry. The optimized molecular geometries of some selected compounds were investigated using the density functional theory (DFT/B3LYP) method with the use of double zeta plus polarization basis set 6–31 G (d,p) for the C, H, N, O and S atoms. The quantum global reactivity descriptors were also calculated and discussed. The antibacterial and cytotoxicity screening of those compounds were performed to determine their therapeutic potential. Molecular docking of the compounds was also examined. The different biological studies as well as the molecular docking were correlated to each other, and supported that the compounds could bind to DNA, possibly, via intercalative mode and showed a various DNA binding potency.

Centrosymmetric paddlewheel copper(II) complexes as potent intercalators: synthesis, crystal structure description and DNA-binding studies

ABSTRACT Two copper(II) paddlewheel carboxylate complexes 1 and 2 of the general formula ACuL4CuA, where A is DMSO (1) and meta-bromopyridine (2) and L is meta-chlorophenyl acetate, have been synthesised, isolated quantitatively, crystallised and characterised using FTIR, UV-Visible spectroscopy, electrochemistry and XRD. FTIR spectra contained all the required peaks with the most prominent peaks those of carboxylate moiety indicating the bridging bidentate carboxylate binding mode. Electrochemistry yielded results typical of complexes containing Cu2+ centres. The structures were completely solved by XRD technique assigning square pyramidal geometry to each copper ion of the dinuclear complexes. The square base is formed by four oxygen atoms of the carboxylate moiety while the apical position is occupied by the fifth oxygen (of the DMSO molecule in 1) or nitrogen of the meta-bromopyridine in complex 2. The DNA-binding potency of the complexes was explored by viscometry, cyclic voltammetry, UV-Visible spectrophotometry and spectrofluorimetry. All these techniques provided coincident results and showed that the complexes bonded with DNA via an intercalative-binding mode. Additionally, these complexes were found to scavenge the free radical DPPH effectively. The complexes add interesting and valuable addition to the existing treasury on the copper paddlewheel complexes and their biological relevance.

Spectroscopic, density functional theory, nonlinear optical properties and in vitro biological studies of Co(II), Ni(II), and Cu(II) complexes of hydrazide Schiff base derivatives

Complexes of three molecularly designed phenylacetohydrazide Schiff base derivatives—N′‐(2‐hydroxybenzylidene)‐2‐phenylacetohydrazid (HL1), N‐(1‐(2‐hydroxyphenyl)ethylidene)‐2‐phenylacetohydrazide (HL2), and N′‐((1‐hydroxynaphthalen‐2‐yl)methylene)‐2‐phenylacetohydrazide (HL3)—with some bivalent metal ions were synthesized and investigated by several spectroscopic and analytical techniques. The crystal structure of HL1 ligand has been solved by conventional X‐ray diffraction technique. Molecular geometries of HL1 and the studied complexes were investigated using the DFT‐B3LYP/GENECP level of theory. Quantum and non‐quantum global reactivity descriptors as well as the nonlinear optical properties were calculated. Biological parameters such as antimicrobial and antioxidant activities, fluorescence quenching studies, and viscosity measurements of the complexes were carried out. Molecular docking studies of HL1 and complexes using Molecular Operating Environment (MOE) software are reported. The different biological studies and the molecular docking were correlated to each other. The biological studies supported that the complexes can bind to DNA via intercalative mode and showed a various DNA binding potency.

Spectroscopic, crystal structural, theoretical and biological studies of phenylacetohydrazide Schiff base derivatives and their copper complexes

Two phenylacetohydrazide Schiff base derivatives: N’-(1-(2-hydroxyphenyl)ethylidene))-2-phenylacetohydrazide, HL1, and N’-((1-hydroxynaphthalen-2-yl)methylene)-2-phenylacetohydrazide, HL2, were synthesized. HL1 dimerizes in presence of HCl, probably via radical mechanism to give (2,2’-((1E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))diphenol (DIM). Thermal reactions of Cu(II) ions with the two Schiff base ligands resulted in formation of the binuclear complexes [(CuL1)2] and [(CuL2)2]. The stoichiometry and structures of the reported compounds were investigated by several spectroscopic and analytical techniques. The structure of the HL1 ligand and its complex [(CuL1)2] as well as the DIM derivative were analyzed by single crystal X-ray analysis. The X-ray analysis revealed the binuclear coordination of the copper complex with the formation of five- and six-membered rings with every ligand. The molecular geometries of the ligands and their copper complexes were investigated using the DFT-B3LYP/GENECP level of theory. The optimized structures of the studied complexes are consistent with the finding of the X-ray analysis. The quantum, non-quantum global reactivity descriptors and the non-linear optical properties were calculated. Biological studies including, antimicrobial and antioxidant activities of the complexes along with fluorescence quenching studies and viscosity measurements are carried out. The molecular docking of the two ligands and [(CuL2)2] complex is also reported. The different biological studies as well as molecular docking are correlated to each other and supported the fact that the complexes can bind to DNA via intercalative mode and showed a various DNA binding potency.

DNA Binding Potency and Antimicrobial Analysis of New Indole and Pyrazolone Based Transition Metal(II) Complexes

Some novel series of 5-chloro isatin and 4-aminoantipyrine based Schiff bases with transition metal(II) complexes of (Cu, Co, Ni and Zn) have been prepared and characterized by physical, analytical and spectral data. The synthesized ligand behaves as a neutral tridentate is confirmed by spectral techniques. During the complexation, the stoichiometry ratio 1:2 (metal:ligand) is followed and an octahedral arrangement is adopted by all the metal complexes. The calf-thymus DNA interacts with complexes via an intercalative mode is studied by electronic absorption titration. Moreover, all these synthesized metal(II) complexes were tested against a set of bacterial and fungal strains reveals that complexes exhibit better activity than free ligand.

Conjugating a groove binder analogue to a styryl-quinolinium scaffold for the light-up detection of duplex and G-Quadruplex DNA with different binding modes.

The rational design of novel small molecules, which can target specific DNA sequences or secondary structural DNAs, is one of the most important goals in medicinal chemistry. Also the studies of DNA binding potency which can give fundamental insight into binding mechanisms and specificity are essential. In this paper, a N-methylated quinolinium probe NSQ functionalized with a G-Quadruplex DNA groove binder analogue was designed and synthesized. NSQ was found to express selective and sensitive for "light-up" detection of both G-Quadruplex and duplex DNAs over RNA and other biomolecules. The characteristics of NSQ and its interactions with DNAs were comprehensively evaluated by means of fluorescence, UV-Vis, circular dichroism, FID assay, DFT calculation and molecular docking. NSQ exhibited higher binding affinity to G-Quadruplex than to duplex DNA. Binding mechanism analysis indicated NSQ interacted with G-Quadruplex DNA mainly through end-stacking mode, while bound with duplex DNA into the minor groove of AT-rich regions. Further, NSQ exhibited potent invitro anti-tumor activity, and to elucidate the cellular applications, confocal cell imaging was carried out and validated its mainly nuclear localization.

Mono- and poly-nuclear copper(II) carboxylates with flourous ligands: Synthesis, structure and improved properties

Polynuclear copper(II) complexes [Cu(para-fluorophenyl acetate)2]n (1) and [Cu(para-nitrophenyl acetate)2]n (2) were converted in-situ to mono-nuclear complexes [Cu(para-fluorophenyl acetate)2(1,10-Phenanthroline)(H2O)] (3) and [Cu(para-nitrophenyl acetate)2(2,2́-Bipyridine)(H2O)].3H2O (4). The complexes were isolated in quantitative yield, purified and characterized using FT-IR, absorption, electrochemical, electron paramagnetic resonance and powder XRD techniques yielding results in accordance with structural data. Structures of 1 and 2 consist of directly interlinked paddlewheel units with square pyramidal geometry while those of 3 and 4 are mononuclear with octahedral and square pyramidal geometry around Cu. Fluorinated complexes 1 and 3 were found to consist of extensive intermolecular interactions while 2 and 4 contained no such interactions. Their optical band gap was around 1.4 eV which indicates semiconducting property of the complexes. Moreover, the flourous complex 3 was found to possess significant activity against Bacillus subtilis and Escherichia coli and good activity against Micrococcus luteus. A similar trend was observed in their DNA-binding potency studied through absorption as well as electrochemical solution studies yielding Kb values 1.494 × 104, 1.342 × 104 and 1.411 × 104 M−1 and 7.547 × 104, 2.457 × 104 and 3.667 × 104 M−1 for 1–3, respectively. The electronic structures of the complexes elucidated using density functional theory ab-initio calculations confirmed the Intermediate states which play important role in the enhancement of the optoelectronic properties. The structure and properties of the flourous complexes were found different than their non-flourous analogues which was attributable to fluorine.

New bioactive ferrocene-substituted heteroleptic copper(I) complex: Synthesis, structural elucidation, DNA interaction, and DFT study

In the present work, a new para-ferrocenylbenzoate copper(I) complex (a4) has been synthesized and characterized by numerous spectroscopic techniques such as: FT-IR, AAS, and CHNS analysis. Moreover, the single-crystal X-ray structure of the compound a4 was also explored. The DNA binding potency was determined by cyclic voltammetry, UV-visible spectroscopy, and viscometry. The redox behavior of the complex studied by cyclic voltammetry revealed a single quasi-reversible voltammogram, attributed to the dominant redox-active ferrocenyl moiety. The electrochemical study reveals that the complex binds to DNA non-covalently, the mode of interaction in particular, was found to be an electrostatic. The DNA binding constant was found to be 4.3 × 104 M−1, which is very significant and impressive for non-covalent interactions, and is in close agreement with the UV-visible spectroscopic results. DFT/B3LYP method was used to ascertain the energies of frontier molecular orbitals (HOMO/LUMO) and the charge distribution on the molecular structure. The ferrocene-based copper(I) complex (a4) demonstrated to be a decent candidate in terms of cytotoxicity, although less active than that of the standard chemotherapeutic drug (cisplatin).

Genome-Wide Mapping of the Binding Sites and Structural Analysis of Kaposi's Sarcoma-Associated Herpesvirus Viral Interferon Regulatory Factor 2 Reveal that It Is a DNA-Binding Transcription Factor.

The oncogenic herpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV) is known to encode four viral interferon regulatory factors (vIRF1 to -4) to subvert the host antiviral immune response, but their detailed DNA-binding profiles as transcription factors in the host remain uncharacterized. Here, we first performed genome-wide vIRF2-binding site mapping in the human genome using chromatin immunoprecipitation coupled with high-throughput sequencing (ChIP-seq). vIRF2 was capable of binding to the promoter regions of 100 putative target genes. Importantly, we confirmed that vIRF2 can specifically interact with the promoters of the genes encoding PIK3C3, HMGCR, and HMGCL, which are associated with autophagosome formation or tumor progression and metastasis, and regulate their transcription in vivo. The crystal structure of the vIRF2 DNA-binding domain (DBD) (referred to here as vIRF2DBD) showed variable loop conformations and positive-charge distributions different from those of vIRF1 and cellular IRFs that are associated with DNA-binding specificities. Structure-based mutagenesis revealed that Arg82 and Arg85 are required for the in vitro DNA-binding activity of vIRF2DBD and can abolish the transcription regulation function of vIRF2 on the promoter reporter activity of PIK3C3, HMGCR, and HMGCL. Collectively, our study provided unique insights into the DNA-binding potency of vIRF2 and suggested that vIRF2 could act as a transcription factor of its target genes in the host antiviral immune response. The oncogenic herpesvirus KSHV is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. KSHV has developed a unique mechanism to subvert the host antiviral immune responses by encoding four homologues of cellular interferon regulatory factors (vIRF1 to -4). However, none of their DNA-binding profiles in the human genome have been characterized until now, and the structural basis for their diverse DNA-binding properties remain poorly understood. In this study, we performed the first genome-wide vIRF2-binding site mapping in the human genome and found vIRF2 can bind to the promoter regions of 100 target cellular genes. X-ray structure analysis and functional studies provided unique insights into its DNA-binding potency and regulation of target gene expression. Our study suggested that vIRF2 could act as a transcription factor of its target genes and contribute to KSHV infection and pathogenesis through versatile functions.

Synthesis, Chemical Characterization, DNA Interaction and Antioxidant, Studies of New Nitrosubstituted Thioureas and Their Copper Complexes

AbstractIn the present work new nitro substituted thioureas, and their copper complexes have been synthesized and characterized by FTIR and multinuclear NMR techniques. Some of the compounds namely 1‐benzoyl‐3‐(4‐chloro‐3‐nitrophenyl) thiourea (A‐1), 1‐benzoyl‐3‐(4‐chloro‐3‐nitrophenyl) thiourea (A‐2) and 1‐benzoyl‐3‐(2‐methoxy‐4‐nitrophenyl) thiourea (A‐2) have also been characterized by single crystal XRD. All the synthesized compounds have been screened for DNA binding potencies (using cyclic voltametry, UV‐vis spectroscopy) and free radical scavanging activities.

Bioactivity of new ferrocene incorporated N,N′-disubstituted ureas: Synthesis, structural elucidation and DFT study

We report here the synthesis, structural characterization and biological assessment of three new ferrocene incorporated ureas (1–3). The synthesis of these complexes was accomplished by the deprotection of ferrocene-based thioureas to the corresponding oxo analogues using NaOH(aq) and mercuric chloride. The new ferrocenyl ureas were characterized by FT-IR, multinuclear (1H and 13C) NMR, AAS and elemental analysis. Furthermore, the single-crystal X-ray structure of compound 2 was also determined. The DNA binding potency of these ureas was evaluated by UV–Vis spectroscopy and cyclic voltammetry (CV). The three complexes interact electrostatically with DNA and have impressive binding constants ranging from 3.42×104 to 8.15×104M−1. The diffusion coefficients of the drug–DNA adducts are lower than is that for the free drug indicating the formation of a high molecular weight complex that diffuses slowly towards the electrode. The small binding site size of 0.509 (1), 0.528 (2) and 0.473 (3) base pairs is also indicative of an electrostatic mode of interaction. The DFT calculated HOMO and LUMO energies correlate well with the experimentally determined redox potential values. The synthesized ureas (1–3) were screened for their antibacterial, antifungal and protein kinase inhibition potency. These compounds play a significant role in arresting microbial growth and are potent protein kinase inhibitors.

Synthesis, structural characterization, DNA binding and antioxidant potency of new ferrocene incorporated acyl ureas

In this article, we have reported the synthesis of three new ferrocene incorporated ureas namely; 1-(4-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea (P4Cl), 1-(3-Chlorobenzoyl)-3-(4-ferrocenyl phenyl)urea (P3Cl) and 1-(2-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea (P2Cl). All new compounds were unambiguously characterized by common analytical techniques (NMR, FT-IR, AAS, CHNS and molecular docking). Furthermore, single crystal XRD analysis was done for 1-(3-Chlorobenzoyl)-3-(4-ferrocenylphenyl)urea. DNA binding is a pre-requisite for a compound to be used as an antitumor agent. The DNA binding study was done by cyclic voltammetry, UV–vis spectroscopy and viscometry. The drug–DNA binding constant was found to vary in the sequence: KP2Cl (6.056 × 104 M−1) > KP4Cl (5.713 × 104 M−1) > KP3Cl (4.631 × 104 M−1). Diffusion coefficient of the drug–DNA adduct for all the compounds is lower than the free drug, indicating that drug–DNA adduct is of higher molecular weight and slow diffusing as compared to the free drug. Small binding site size of 0.440 (P3Cl), 0.585 (P4Cl) and 0.673 (P2Cl) base pairs is consistent with electrostatic interaction. All the compounds exhibited good antioxidant activities with IC50 values of 82, 136 and 54 μM for P4Cl, P3Cl and P2Cl respectively, against DPPH.

Preliminary investigation of anticancer activity by determining the DNA binding and antioxidant potency of new ferrocene incorporated N,N′,N″-trisubstituted phenylguanidines

Six new bioactive ferrocene based phenylguanidines were successively synthesized and characterized by means of various analytical techniques like elemental analysis, FT-IR, multinuclear (1H and 13C) NMR, UV–Vis spectroscopy and cyclic voltammetry. The interaction of compounds with DNA was investigated by spectroscopic and cyclic voltammetric measurements. The interaction was found to be the electrostatic and the binding constants values were impressively larger. Compounds f-1, f-2, f-3 have slight larger binding constant values ranging from 0.8×105 to 2.4×105 as compared to g-1, g-2 and g-3 ranging from 7.6×104 to 1.1×105 which is most probably due to the presence of ferrocene at para position where the delocalization of electrons is maximum. Antioxidant activity was determined by UV–Vis spectrophotometer by using DPPH as a free radical. All the compounds exhibit good antioxidant activity and the results so obtained support the structure activity relationship.

EGCG debilitates the persistence of EBV latency by reducing the DNA binding potency of nuclear antigen 1

Because the expression of EBNA1 is prevalent in all EBV-associated tumors, it has become one of the most attractive drug targets for the discovery of anti-EBV compounds. In a cell-based reporter system, EBNA1 consistently upregulated the transcription of an oriP-Luc mini-EBV episome by 6- to 8-fold. The treatment of cells with 50μM EGCG effectively blocked the binding of EBNA1 to oriP-DNA both in vivo and in vitro, which led to the abrogation of EBNA1-dependent episome maintenance and transcriptional enhancement. Importantly, the anti-EBNA1 effects caused by EGCG ultimately impaired the persistence of EBV latent infection. Our data suggest that the inhibition of EBNA1 activity by EGCG could be a promising starting point for the development of new protocols for anti-EBV therapy.

477 POSTER Sequence-selective inhibition of the DNA binding potencies of Pit-1 and Brn-3 transcription factors by phenyl-furan-benzimidazole DNA ligands

477 POSTER Sequence-selective inhibition of the DNA binding potencies of Pit-1 and Brn-3 transcription factors by phenyl-furan-benzimidazole DNA ligands

The genotoxic effect of carcinogenic PAHs, their artificial and environmental mixtures (EOM) on human diploid lung fibroblasts

The aim of this study was to investigate the genotoxic effect of single carcinogenic polycyclic aromatic hydrocarbons (c-PAHs), as well as their binary and artificial mixtures containing c-PAHs in the same relative proportions as real complex mixtures, and to investigate the genotoxic effect of environmental mixtures such as EOM (extractable organic matter adsorbed to respirable air particles). We used normal human diploid lung fibroblasts (HEL) in a confluent (“quiescent”) state as being closer to in vivo conditions. We determined DNA adducts by 32 P -postlabelling and the expression of p53 and p21 WAF1 proteins by Western blotting. Our results showed that the DNA binding potencies of c-PAHs in quiescent HEL cells were as follows: DB[al]P⪢B[a]P⪢B[b]F∼CHRY∼B[k]F∼B[a]A∼DB[ah]A∼I[cd]P>B[ghi]P. Both DB[al]P and B[a]P were chosen to assess the genotoxic effect of other c-PAHs when present in binary mixtures. In all cases, co-treatment resulted in significantly lower DNA adduct levels as compared with adduct levels resulting from single compounds. The highest inhibitory effect was found in the presence of DB[ah]A followed by B[k]F. In both artificial and EOM mixtures a strong inhibitory effect of other compounds was observed. BPDE-adduct levels were up to five-fold lower in an artificial c-PAH mixture and up to 10-fold lower in an EOM sample than expected from applying B[a]P alone at the same concentration. These results suggest a competition for the metabolic activation enzymes, their saturation and/or inactivation by PAH metabolites. We did not observe the decrease of DNA adducts and induced levels of both p53 and p21 WAF1 proteins during the post-treatment period up to 6 days following exposure. We suggest that parent c-PAHs accumulate inside cells and that they are further activated by newly synthesised enzymes during the post-treatment period. Therefore, unaltered c-PAHs may act as a reservoir inside the cells for the long-term production of active metabolites. The total DNA adduct levels induced in HEL cells after exposure to EOM were generally low as compared with exposure to B[a]P alone under the same conditions. Human diploid lung fibroblasts possess low metabolic capacity than other human target cells. Therefore, it may be easier to competitively inhibit the metabolising enzymes in this cell system. We hypothesise that this finding might explain the generally low PAH–DNA adduct levels detected in human studies using surrogate cells such as blood WBC or lymphocytes that also possess low metabolic capacity.