Publications by authors named "Mozhgan Khorasani-Motlagh"

38 Publications

A novel mode of control of nickel uptake by a multifunctional metallochaperone.

PLoS Pathog 2021 01 14;17(1):e1009193. Epub 2021 Jan 14.

Institut Pasteur, Département de Microbiologie, Unité Pathogenèse de Helicobacter, CNRS UMR 2001, Paris, France.

Cellular metal homeostasis is a critical process for all organisms, requiring tight regulation. In the major pathogen Helicobacter pylori, the acquisition of nickel is an essential virulence determinant as this metal is a cofactor for the acid-resistance enzyme, urease. Nickel uptake relies on the NixA permease and the NiuBDE ABC transporter. Till now, bacterial metal transporters were reported to be controlled at their transcriptional level. Here we uncovered post-translational regulation of the essential Niu transporter in H. pylori. Indeed, we demonstrate that SlyD, a protein combining peptidyl-prolyl isomerase (PPIase), chaperone, and metal-binding properties, is required for the activity of the Niu transporter. Using two-hybrid assays, we found that SlyD directly interacts with the NiuD permease subunit and identified a motif critical for this contact. Mutants of the different SlyD functional domains were constructed and used to perform in vitro PPIase activity assays and four different in vivo tests measuring nickel intracellular accumulation or transport in H. pylori. In vitro, SlyD PPIase activity is down-regulated by nickel, independently of its C-terminal region reported to bind metals. In vivo, a role of SlyD PPIase function was only revealed upon exposure to high nickel concentrations. Most importantly, the IF chaperone domain of SlyD was shown to be mandatory for Niu activation under all in vivo conditions. These data suggest that SlyD is required for the active functional conformation of the Niu permease and regulates its activity through a novel mechanism implying direct protein interaction, thereby acting as a gatekeeper of nickel uptake. Finally, in agreement with a central role of SlyD, this protein is essential for the colonization of the mouse model by H. pylori.
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http://dx.doi.org/10.1371/journal.ppat.1009193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7840056PMC
January 2021

Experimental and computational interaction studies of terbium (III) and lanthanide (III) complexes containing 2,2'-bipyridine with bovine serum albumin and their anticancer and antimicrobial activities.

J Biomol Struct Dyn 2020 Jul 16:1-12. Epub 2020 Jul 16.

Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, ON, Canada.

To investigate the chemotherapeutic and pharmacokinetic aspects of two lanthanide complexes (Tb(III) and La(III) containing 2,2'-bipyridine ligand), binding studies were carried out with BSA by employing multiple biophysical methods and molecular modeling study. There are different techniques containing fluorescence, absorption spectroscopy and competitive experiments to determine the interaction mode between BSA and these complexes. These complexes efficiently quenched the BSA emission through a static procedure. The results showed that the terbium and lanthanum complexes exhibited a high propensity for BSA interaction van der Waals force. Further, competitive examination and docking study showed that the interaction site of these complexes on BSA is site III. The results of docking calculations were in good agreement with experimental examinations. Also, the energy transfer from BSA to these complexes has happened with high possibility. Moreover, antimicrobial studies of different bacterial and fungi indicated its promising antibacterial activity. cytotoxicity of the Tb complex and La complex was carried out in MCF-7 and A-549 cell lines, which revealed significantly good activity.Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2020.1792988DOI Listing
July 2020

Evaluation of parent and nano-encapsulated terbium(III) complex toward its photoluminescence properties, FS-DNA, BSA binding affinity, and biological applications.

J Trace Elem Med Biol 2020 May 21;61:126564. Epub 2020 May 21.

Department of Physical and Environmental Sciences, University of Toronto Scarborough 1265 Military Trail, Toronto, Ontario, M1C 1A4, Canada. Electronic address:

Background: There is a crucial need for finding and developing new compounds as the anticancer and antimicrobial agents with better activity, specific target, and less toxic side effects.

Objectives: Base on the potential anticancer properties of lanthanide complexes, in the paper, the biological applications of terbium (Tb) complex, containing 2,9-dimethyl- 1,10-phenanthroline (MePhen) such as anticancer, antimicrobial, DNA cleavage ability, the interaction with FS-DNA (Fish-Salmon DNA) and BSA (Bovine Serum Albumin) was examined.

Methods: The interaction of Tb-complex with BSA and DNA was studied by emission spectroscopy, absorption titration, viscosity measurement, CD spectroscopy, competitive experiments, and docking calculation. Also, the ability of this complex to cleave DNA was reported by gel electrophoresis. Tb-complex was concurrently screened for its antibacterial activities by different methods. Besides, the nanocarriers of Tb-complex (lipid nanoencapsulation (LNEP) and the starch nanoencapsulation (SNEP)), as active anticancer candidates, were prepared. MTT technique was applied to measure the antitumor properties of these compounds on human cancer cell lines.

Results: The experimental and docking results suggest significant binding between DNA as well as BSA with terbium-complex. Besides, groove binding plays the main role in the binding of this compound with DNA and BSA. The competitive experiment with hemin demonstrated that the terbium complex was bound at site III of BSA, which was confirmed by the docking study. Also, Tb-complex was concurrently screened for its DNA cleavage, antimicrobial, and anticancer activities. The anticancer properties of LNEP and SNEP are more than the terbium compound.

Conclusions: Tb-complex can bond to DNA/BSA with high binding affinity. Base on biological applications of Tb-complex, it can be concluded that this complex and its nanocarriers can suggest as novel anticancer, antimicrobial candidates.
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http://dx.doi.org/10.1016/j.jtemb.2020.126564DOI Listing
May 2020

Experimental and theoretical investigations of Dy(III) complex with 2,2'-bipyridine ligand: DNA and BSA interactions and antimicrobial activity study.

J Biomol Struct Dyn 2020 Oct 14;38(16):4746-4763. Epub 2019 Nov 14.

Department of Physical and Environmental Sciences, University of Toronto Scarborough, Toronto, Ontario, Canada.

In this study, the interactions of a novel metal complex [Dy(bpy)Cl.OH] (bpy is 2,2'-bipyridine) with fish salmon DNA (FS-DNA) and bovine serum albumin (BSA) were investigated by experimental and theoretical methods. All results suggested significant binding between the Dy(III) complex with FS-DNA and BSA. The binding constants (), Stern-Volmer quenching constants () of Dy(III)-complex with FS-DNA and BSA at various temperatures as well as thermodynamic parameters using Van't Hoff equation were obtained. The experimental results from absorption, ionic strength, iodide ion quenching, ethidium bromide (EtBr) quenching studies and positive Δ˚ and Δ˚ suggested that hydrophobic groove-binding mode played a predominant role in the binding of Dy(III)-complex with FS-DNA. Indeed, the molecular docking results for DNA-binding were in agreement with experimental data. Besides, the results found from experimental and molecular modeling indicated that the Dy(III)complex bound to BSA Van der Waals interactions. Moreover, the results of competitive tests by phenylbutazone, ibuprofen, and hemin (as a site-I, site-II and site-III markers, respectively) considered that the site-III of BSA is the most possible binding site for Dy(III)-complex. In addition, Dy(III) complex was concurrently screened for its antimicrobial activities. The presented data provide a promising platform for the development of novel metal complexes that target nucleic acids and proteins with antimicrobial activity.Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2019.1689170DOI Listing
October 2020

Bimodal Nickel-Binding Site on [NiFe]-Hydrogenase Metallochaperone HypA.

Inorg Chem 2019 Oct 5;58(20):13604-13618. Epub 2019 Jul 5.

Department of Chemistry , University of Toronto , Toronto , Ontario M5S 3H6 , Canada.

[NiFe]-hydrogenase enzymes catalyze the reversible oxidation of hydrogen at a bimetallic cluster and are used by bacteria and archaea for anaerobic growth and pathogenesis. Maturation of the [NiFe]-hydrogenase requires several accessory proteins to assemble and insert the components of the active site. The penultimate maturation step is the delivery of nickel to a primed hydrogenase enzyme precursor protein, a process that is accomplished by two nickel metallochaperones, the accessory protein HypA and the GTPase HypB. Recent work demonstrated that nickel is rapidly transferred to HypA from GDP-loaded HypB within the context of a protein complex in a nickel selective and unidirectional process. To investigate the mechanism of metal transfer, we examined the allosteric effects of nucleotide cofactors and partner proteins on the nickel environments of HypA and HypB by using a combination of biochemical, microbiological, computational, and spectroscopic techniques. We observed that loading HypB with either GDP or a nonhydrolyzable GTP analogue resulted in a similar nickel environment. In addition, interaction with a mutant version of HypA with disrupted nickel binding, H2Q-HypA, does not induce substantial changes to the HypB G-domain nickel site. Instead, the results demonstrate that HypB modifies the acceptor site of HypA. Analysis of a peptide maquette derived from the N-terminus of HypA revealed that nickel is predominately coordinated by atoms from the N-terminal Met-His motif. Furthermore, HypA is capable of two nickel-binding modes at the N-terminus, a HypB-induced mode and a binding mode that mirrors the peptide maquette. Collectively, these results reveal that HypB brings about changes in the nickel coordination of HypA, providing a mechanism for the HypB-dependent control of the acquisition and release of nickel by HypA.
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http://dx.doi.org/10.1021/acs.inorgchem.9b00897DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6803039PMC
October 2019

Evaluation of DNA, BSA binding, DNA cleavage and antimicrobial activity of ytterbium(III) complex containing 2,2'-bipyridine ligand.

J Biomol Struct Dyn 2020 Apr 27;38(6):1711-1725. Epub 2019 May 27.

Department of Chemistry, University of Sistan and Baluchestan, Zahedan, Iran.

In order to estimate the biological potential of a synthesized complex [Yb(bpy)Cl.OH] where bpy is 2,2'-bipyridine, its binding behavior with fish salmon-DNA (FS-DNA) and bovine serum albumin (BSA) were studied by different kinds of spectroscopy and molecular modeling methods. This complex was selected for its antibacterial and antifungal activities as well as the DNA cleavage activities were examined by agarose gel electrophoresis. The analyses of fluorescence data at four temperatures were done in order to evaluate the binding and thermodynamic parameters of the interaction of Yb(III) complex with DNA and BSA. The experimental results indicated that the major binding modes were based on groove binding with DNA and BSA. In addition, iodide quenching studies, ethidium bromide (EtBr) exclusion assay, ionic strength effect, circular dichroism, and viscosity studies reflected the binding of Yb(III) complex explicitly with the FS-DNA mainly in a groove binding mode. Moreover, molecular docking studies indicated that this complex was bound to the minor groove of DNA and to polar and apolar residues located in the subdomain IB of BSA (site 3). Also, the results of competitive experiments assessed site 3 of BSA as the most probable binding site for this complex. The molecular docking results were in good agreement with our experimental results. From both experimental and docking results, the binding constant values displayed the remarkably high affinity of Yb(III) complex to DNA as well as BSA.Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2019.1617788DOI Listing
April 2020

Complex formation between the Escherichia coli [NiFe]-hydrogenase nickel maturation factors.

Biometals 2019 06 13;32(3):521-532. Epub 2019 Feb 13.

Department of Chemistry, University of Toronto, Toronto, ON, M5S 3H6, Canada.

The biosynthesis of the dinuclear metal cluster at the active sites of the [NiFe]-hydrogenase enzymes is a multi-step process executed by a suite of accessory proteins. Nickel insertion during maturation of Escherichia coli [NiFe]-hydrogenase 3 is achieved by the metallochaperones HypA, SlyD and the GTPase HypB, but how these proteins cooperate to ensure nickel delivery is not known. In this study, the complexes formed between the individual purified proteins were examined by using several methods. Size exclusion chromatography (SEC) indicated that SlyD and HypB interact primarily in a 1:1 complex. The affinity of HypB-SlyD was measured by using surface plasmon resonance, which revealed a K of 24 ± 10 nM in the absence of nucleotide and an interaction several fold tighter in the presence of GDP. A ternary complex between all three proteins was not detected, and instead SlyD blocked the interaction of HypA with HypB in competitive binding experiments. Furthermore, cross-linking experiments suggest a weak interaction between HypA and SlyD, which is not detectable by SEC. Electrochemical analysis confirmed each of the pairwise interactions and that the relative affinities of these complexes are on the order of HypB-SlyD > HypB-HypA > HypA-SlyD. These results indicate a hierarchy of interactions, as opposed to a single multiprotein complex, and provide insight into the nickel delivery process during hydrogenase enzyme maturation.
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http://dx.doi.org/10.1007/s10534-019-00173-9DOI Listing
June 2019

cytotoxicity studies of parent and nanoencapsulated Holmium-2,9-dimethyl-1,10-phenanthroline complex toward fish-salmon DNA-binding properties and antibacterial activity.

J Biomol Struct Dyn 2019 10 16;37(17):4437-4449. Epub 2019 Jan 16.

Department of Biotechnology, Institute of Science, High Technology & Environmental Science, Graduate University of Advance Technology , Kerman , Iran.

In this study, the interaction of Holmium (Ho) complex including 2, 9-dimethyl-1,10-phenanthroline, also called Neocuproine (Neo), [Ho(Neo)Cl.HO], as fluorescence probe with fish-salmon DNA (FS-DNA) is studied during experimental investigations. Multi-spectroscopic methods are utilized to determine the affinity binding constants () of complex-FS-DNA. It is found that fluorescence of Ho complex is strongly quenched by the FS-DNA through a static quenching procedure. Under optimal conditions in Tris(trishydroxymethyl-aminomethane)-HCl buffer at 25 °C with pH ≈ 7.2, intrinsic binding constant of Ho complex is 6.12 ± 0.04 × 10 M. Also, the binding site number and Stern-Volmer quenching constant are calculated. There are different approaches, including iodide quenching assay, salt effect and thermodynamical assessment to determine the features of the binding mode between Ho complex and FS-DNA. Also, the parent and starch and lipid nanoencapsulated Ho complex, as potent antitumor candidates, were synthesized. The main structure of Ho complex is maintained after encapsulation using starch and lipid nanoparticles. 3-[4,5-Dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) method was used to assess the anticancer properties of Ho complex and its encapsulated forms on human cancer cell lines of human lung carcinoma cell line and breast cancer cell line. In conclusion, these compounds could be considered as new antitumor candidates. Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2018.1557077DOI Listing
October 2019

Electronic and fluorescent studies on the interaction of DNA and BSA with a new ternary praseodymium complex containing 2,9-dimethyl 1,10-phenanthroline and antibacterial activities testing.

J Biomol Struct Dyn 2019 Jun 1;37(9):2283-2295. Epub 2018 Nov 1.

a Department of Chemistry , University of Sistan and Baluchestan , Zahedan , Iran.

In this study, fluorescence emission spectra, UV-vis absorption spectra, ethidium bromide (EB)-competition experiment, and iodide quenching experiment were used for the interaction study of the Fish salmon DNA (FS-DNA) with [Pr(dmp)2Cl3(OH2)] where dmp is 2,9-dimethyl 1,10-phenanthroline. The binding constant and the number of binding sites of the complex with FS-DNA were 6.09 ± 0.04 M and 1.18, respectively. The free energy, enthalpy, and entropy changes (ΔG°, ΔH°, and ΔS°) in the binding process of the Pr(III) complex with FS-DNA were -8.02 kcal mol, +39.44 kcal mol1, and +159.56 cal mol K, respectively. Based on these results, the interaction process between FS-DNA with [Pr(dmp)2Cl3(OH2)] was spontaneous and the main binding interaction force was groove binding mode. Also, Fluorescence and electronic absorption spectroscopy were used in order to evaluate the binding characteristics, stoichiometry, and interaction mode of praseodymium(III) (Pr(III)) complex with bovine serum albumin (BSA). Title complex showed good binding propensity to BSA presenting moderately high Kb values. The fluorescence quenching of BSA by Pr(III) complex has been observed to be the static process. The positive ΔH° and ΔS° values showed that the hydrophobic interaction is the main force in the binding of Pr(III) complex and BSA. Eventually, the average aggregation number, , of BSA potentially induced by title complex confirmed the 1:1 stoichiometry for title complex-BSA adducts. In vitro, antimicrobial activity of title complex was indicated that the complex is more active against both Escherichia coli and Enterococcus faecalis bacterial strains than Staphylococcus aureus, and Pseudomonas aeruginosa. Communicated by Ramaswamy H. Sarma.
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http://dx.doi.org/10.1080/07391102.2018.1479657DOI Listing
June 2019

Synthesis, characterization, and binding assessment with human serum albumin of three bipyridine lanthanide(III) complexes.

J Biomol Struct Dyn 2019 Apr 18;37(6):1438-1450. Epub 2018 May 18.

b Department of Chemistry , University of Sistan & Baluchestan , Zahedan 98155-147 , Iran.

In this work, the terbium(III), dysprosium(III), and ytterbium(III) complexes containing 2, 2'-bipyridine (bpy) ligand have been synthesized and characterized using CHN elemental analysis, FT-IR, UV-Vis and H-NMR techniques and their binding behavior with human serum albumin (HSA) was studied by UV-Vis, fluorescence and molecular docking examinations. The experimental data indicated that all three lanthanide complexes have high binding affinity to HSA with effective quenching of HSA fluorescence via static mechanism. The binding parameters, the type of interaction, the value of resonance energy transfer, and the binding distance between complexes and HSA were estimated from the analysis of fluorescence measurements and Förster theory. The thermodynamic parameters suggested that van der Waals interactions and hydrogen bonds play an important role in the binding mechanism. While, the energy transfer from HSA molecules to all these complexes occurs with high probability, the order of binding constants (BpyTb > BpyDy > BpyYb) represents the importance of radius of Ln ion in the complex-HSA interaction. The results of molecular docking calculation and competitive experiments assessed site 3 of HSA, located in subdomain IB, as the most probable binding site for these ligands and also indicated the microenvironment residues around the bound mentioned complexes. The computational results kept in good agreement with experimental data.
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http://dx.doi.org/10.1080/07391102.2018.1464959DOI Listing
April 2019

High-affinity metal binding by the Escherichia coli [NiFe]-hydrogenase accessory protein HypB is selectively modulated by SlyD.

Metallomics 2017 05;9(5):482-493

Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada.

[NiFe]-hydrogenase, which catalyzes the reversible conversion between hydrogen gas and protons, is a vital component of the metabolism of many pathogens. Maturation of [NiFe]-hydrogenase requires selective nickel insertion that is completed, in part, by the metallochaperones SlyD and HypB. Escherichia coli HypB binds nickel with sub-picomolar affinity, and the formation of the HypB-SlyD complex activates nickel release from the high-affinity site (HAS) of HypB. In this study, the metal selectivity of this process was investigated. Biochemical experiments revealed that the HAS of full length HypB can bind stoichiometric zinc. Moreover, in contrast to the acceleration of metal release observed with nickel-loaded HypB, SlyD blocks the release of zinc from the HypB HAS. X-ray absorption spectroscopy (XAS) demonstrated that SlyD does not impact the primary coordination sphere of nickel or zinc bound to the HAS of HypB. Instead, computational modeling and XAS of HypB loaded with nickel or zinc indicated that zinc binds to HypB with a different coordination sphere than nickel. The data suggested that Glu9, which is not a nickel ligand, directly coordinates zinc. These results were confirmed through the characterization of E9A-HypB, which afforded weakened zinc affinity compared to wild-type HypB but similar nickel affinity. This mutant HypB fully supports the production of [NiFe]-hydrogenase in E. coli. Altogether, these results are consistent with the model that the HAS of HypB functions as a nickel site during [NiFe]-hydrogenase enzyme maturation and that the metal selectivity is controlled by activation of metal release by SlyD.
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http://dx.doi.org/10.1039/c7mt00037eDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5473619PMC
May 2017

Evaluation of DNA, BSA binding, and antimicrobial activity of new synthesized neodymium complex containing 29-dimethyl 110-phenanthroline.

J Biomol Struct Dyn 2018 02 21;36(3):779-794. Epub 2017 Feb 21.

a Department of Chemistry , University of Sistan and Baluchestan , Zahedan , P.O. Box 98155-147 , Iran.

In order to evaluate biological potential of a novel synthesized complex [Nd(dmp)Cl.OH] where dmp is 29-dimethyl 110-phenanthroline, the DNA-binding, cleavage, BSA binding, and antimicrobial activity properties of the complex are investigated by multispectroscopic techniques study in physiological buffer (pH 7.2).The intrinsic binding constant (K) for interaction of Nd(III) complex and FS-DNA is calculated by UV-Vis (K = 2.7 ± 0.07 × 10) and fluorescence spectroscopy (K = 1.13 ± 0.03 × 10). The Stern-Volmer constant (K), thermodynamic parameters including free energy change (ΔG°), enthalpy change (∆H°), and entropy change (∆S°), are calculated by fluorescent data and Vant' Hoff equation. The experimental results show that the complex can bind to FS-DNA and the major binding mode is groove binding. Meanwhile, the interaction of Nd(III) complex with protein, bovine serum albumin (BSA), has also been studied by using absorption and emission spectroscopic tools. The experimental results show that the complex exhibits good binding propensity to BSA. The positive ΔH° and ∆S° values indicate that the hydrophobic interaction is main force in the binding of the Nd(III) complex to BSA, and the complex can quench the intrinsic fluorescence of BSA remarkably through a static quenching process. Also, DNA cleavage was investigated by agarose gel electrophoresis that according to the results cleavage of DNA increased with increasing of concentration of the complex. Antimicrobial screening test gives good results in the presence of Nd(III) complex system.
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http://dx.doi.org/10.1080/07391102.2017.1288170DOI Listing
February 2018

Evaluation DNA-/BSA-binding properties of a new europium complex containing 2,9-dimethyl-1,10-phenanthroline.

J Biomol Struct Dyn 2017 05 11;35(7):1518-1528. Epub 2016 Aug 11.

a Department of Chemistry , University of Sistan and Baluchestan , Zahedan , Iran.

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http://dx.doi.org/10.1080/07391102.2016.1188419DOI Listing
May 2017

Synthesis and biological evaluation of a new dysprosium(III) complex containing 2,9-dimethyl 1,10-phenanthroline.

J Biomol Struct Dyn 2017 Feb 14;35(2):300-311. Epub 2016 Apr 14.

a Department of Chemistry , University of Sistan and Baluchestan , P.O. Box 98155-147, Zahedan , Iran.

The binding of [Dy(dmp)Cl(OH)], where dmp is 2,9-dimethyl 1,10-phenanthroline, with Fish salmon DNA (FS-DNA) is investigated by absorption and emission spectroscopy, quenching studies, salt dependent, and gel electrophoresis. The binding constant (K) of the interaction is calculated as (1.27 ± .05) × 10 M from absorption spectral titration data. The Stern-Volmer constant (K), thermodynamic parameters involves ΔG°, ∆H°, and ∆S° are calculated by fluorescent data and Van't Hoff equation. The thermodynamic studies show that the reaction for the binding of the complex with FS-DNA is endothermic and entropically driven (ΔS° > 0, ΔH° > 0). The effect of the complex concentration on FS-DNA cleavage reactions is also investigated by gel electrophoresis. Furthermore, the Dy(III) complex has been screened for its antibacterial activity. The experimental results suggest that the Dy(III) complex binds significantly to FS-DNA by hydrophobic groove binding mode and the complex has more efficient antibacterial activity compared to its metal salt.
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http://dx.doi.org/10.1080/07391102.2015.1137491DOI Listing
February 2017

DNA interaction of europium(III) complex containing 2,2'-bipyridine and its antimicrobial activity.

J Biomol Struct Dyn 2016 8;34(3):612-24. Epub 2015 Jun 8.

a Department of Chemistry , University of Sistan and Baluchestan , Zahedan , P.O. Box 98155-147, Iran.

The interaction of native fish salmon DNA (FS-DNA) with [Eu(bpy)3Cl2(H2O)]Cl, where bpy is 2,2'-bipyridine, is studied at physiological pH in Tris-HCl buffer by spectroscopic methods, viscometric techniques as well as circular dichroism (CD). These experiments reveal that Eu(III) complex has interaction with FS-DNA. Moreover, binding constant and binding site size have been determined. The value of Kb has been defined 2.46 ± .02 × 10(5) M(-1). The thermodynamic parameters are calculated by Van't Hoff equation, the results show that the interaction of the complex with FS-DNA is an entropically driven phenomenon. CD spectroscopy followed by viscosity as well as fluorescence and UV--Vis measurements indicate that the complex interacts with FS-DNA via groove binding mode. Also, the synthesized Eu(III) complex has been screened for antimicrobial activities.
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http://dx.doi.org/10.1080/07391102.2015.1048481DOI Listing
December 2016

Multispectroscopic DNA-binding studies of a terbium(III) complex containing 2,2'-bipyridine ligand.

J Biomol Struct Dyn 2016 23;34(2):414-26. Epub 2015 Jun 23.

a Department of Chemistry , University of Sistan and Baluchestan , P.O. Box 98155-147, Zahedan , Iran.

Agarose gel electrophoresis, absorption, fluorescence, viscosity, and circular dichroism (CD) have been used in exploring the interaction of terbium(III) complex, [Tb(bpy)2Cl3(OH2)] where bipy is 2,2'-bipyridine, with Fish salmon DNA. Agarose gel electrophoresis assay, along with absorption and fluorescence studies, reveal interaction between the corresponding complex and FS-DNA. Also, the binding constants (Kb) and the Stern-Volmer quenching constants (Ksv) of Tb(III) complex with FS-DNA were determined. The calculated thermodynamic parameters suggested that the binding of mentioned complex to FS-DNA was driven mainly by hydrophobic interactions. A comparative study of this complex with respect to the effect of iodide-induced quenching, ionic strength effect, and ethidium bromide exclusion assay reflects binding of explicit to the FS-DNA primarily in a groove fashion. CD and viscosity data also support the groove binding mode. Furthermore, Tb(III) complex have been simultaneously screened for their antibacterial and antifungal activities.
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http://dx.doi.org/10.1080/07391102.2015.1038585DOI Listing
October 2016

Development of glassy carbon electrode modified with ruthenium red-multiwalled carbon nanotubes for simultaneous determination of epinephrine and acetaminophen.

Anal Sci 2014 ;30(9):911-8

Department of Chemistry, University of Sistan and Baluchestan.

A glassy carbon electrode modified with ruthenium red and functionalized multi-walled carbon nanotube has been developed. The electrochemical response characteristics of the modified electrode toward epinephrine (EP) and acetaminophen (AC) was investigated by differential pulse voltammetry (DPV). Linear calibration plots were obtained over the range of 0.3 - 333.3 μM for both EP and AC with sensitivities of 0.221 and 0.174 μA μM(-1) for EP and AC, respectively. The detection limits for EP and AC were 0.04 and 0.06 μM, respectively. The diffusion coefficients for the oxidation of EP and AC at the modified electrode were calculated as 2.74 ± 0.05 × 10(-5) and 1.75 ± 0.07 × 10(-5) cm(2) s(-1), respectively. The practical analytical utilities of the modified electrode were demonstrated by the determination of EP and AC in human urine and serum as well as AC tablet samples.
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http://dx.doi.org/10.2116/analsci.30.911DOI Listing
May 2015

Fluorescence studies, DNA binding properties and antimicrobial activity of a dysprosium(III) complex containing 1,10-phenanthroline.

J Photochem Photobiol B 2013 Oct 29;127:192-201. Epub 2013 Aug 29.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran. Electronic address:

Luminescence and binding properties of dysprosium(III) complex containing 1,10-phenanthroline (phen), [Dy(phen)2(OH2)3Cl]Cl2⋅H2O with DNA has been studied by electronic absorption, emission spectroscopy and viscosity measurement. The thermodynamic studies suggest that the interaction process to be endothermic and entropically driven, which indicates that the dysprosium(III) complex might interact with DNA by a non intercalation binding mode. Additionally, the competitive fluorescence study with ethidium bromide and also the effect of iodide ion and salt concentration on fluorescence of the complex-DNA system is investigated. Experimental results indicate that the Dy(III) complex strongly binds to DNA, presumably via groove binding mode. Furthermore, the complex shows a potent antibacterial activity and DNA cleavage ability.
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http://dx.doi.org/10.1016/j.jphotobiol.2013.08.009DOI Listing
October 2013

Biochemical investigation of yttrium(III) complex containing 1,10-phenanthroline: DNA binding and antibacterial activity.

J Photochem Photobiol B 2013 Mar 4;120:148-55. Epub 2013 Jan 4.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran.

Characterization of the interaction between yttrium(III) complex containing 1,10-phenanthroline as ligand, [Y(phen)2Cl(OH2)3]Cl2⋅H2O, and DNA has been carried out by UV absorption, fluorescence spectra and viscosity measurements in order to investigate binding mode. The experimental results indicate that the yttrium(III) complex binds to DNA and absorption is decreasing in charge transfer band with the increase in amount of DNA. The binding constant (Kb) at different temperatures as well as thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), were calculated according to relevant fluorescent data and Vant' Hoff equation. The results of interaction mechanism studies, suggested that groove binding plays a major role in the binding of the complex and DNA. The activity of yttrium(III) complex against some bacteria was tested and antimicrobial screening tests shown growth inhibitory activity in the presence of yttrium(III) complex.
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http://dx.doi.org/10.1016/j.jphotobiol.2012.12.010DOI Listing
March 2013

Spectroscopic studies on the binding of holmium-1,10-phenanthroline complex with DNA.

J Photochem Photobiol B 2012 Dec 11;117:132-9. Epub 2012 Oct 11.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran.

Fluorescence and absorption spectroscopy, circular dichroism (CD) as well as viscosity experiment have been used to characterize the DNA binding of [Ho(Phen)(2)Cl(3)]·H(2)O, where phen stand for 1,10-phanathroline. This complex exhibits the marked decrease in the emission intensity and some hypochromism in UV-Vis spectrum in the presence of DNA. For characterization of the binding mode between the Ho(III) complex and DNA various procedures such as: absorption and emission titration and EB quenching experiments, viscosity measurements, CD study, iodide quenching assay, salt effect and thermodynamical investigation are used. The intrinsic binding constant of [Ho(Phen)(2)Cl(3)]·H(2)O with DNA is calculated by UV-Vis and florescence spectroscopy. The value of binding constants in 296, 299 and 303 are 1.99 ± 0.07 × 10(4), 1.07 ± 0.09 × 10(4) and 0.84 ± 0.06 × 10(4), respectively. The thermodynamic studies show that the reaction is entropically driven. The above-mentioned physical measurements indicate that the Ho(III) complex binds to fish salmon DNA, presumably via groove binding mode.
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http://dx.doi.org/10.1016/j.jphotobiol.2012.09.015DOI Listing
December 2012

Binding analysis of ytterbium(III) complex containing 1,10-phenanthroline with DNA and its antimicrobial activity.

J Biomol Struct Dyn 2013 11;31(8):937-50. Epub 2012 Sep 11.

Department of Chemistry, University of Sistan & Baluchestan, Zahedan 98155-147, Iran.

To evaluate the biological preference of [Yb(phen)₂(OH₂)Cl₃](H₂O)₂ (phen is 1,10-phenanthroline) for DNA, interaction of Yb(III) complex with DNA in Tris-HCl buffer is studied by various biophysical and spectroscopic techniques which reveal that the complex binds to DNA. The results of fluorescence titration reveal that [Yb(phen)₂(OH₂)Cl₃](H₂O)₂ has strongly quenched in the presence of DNA. The binding site number n, apparent binding constant K b, and the Stern-Volmer quenching constant K SV are determined. ΔH⁰, ΔS⁰, and ΔG⁰ are obtained based on the quenching constants and thermodynamic theory (ΔH⁰ > 0, ΔS⁰ > 0, and ΔG⁰ < 0). The experimental results show that the Yb(III) complex binds to DNA by non-intercalative mode. Groove binding is the preferred mode of interaction for [Yb(phen)₂(OH₂)Cl₃](H₂O)₂ to DNA. The DNA cleavage results show that in the absence of any reducing agent, Yb(III) complex can cleave DNA. The antimicrobial screening tests are also recorded and give good results in the presence of Yb(III) complex.
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http://dx.doi.org/10.1080/07391102.2012.718525DOI Listing
February 2014

Preparation of tetraheptylammonium iodide-iodine graphite-multiwall carbon nanotube paste electrode: electrocatalytic determination of ascorbic acid in pharmaceuticals and foods.

Anal Sci 2011 ;27(9):929-35

Analytical Research Laboratory, Department of Chemistry, University of Sistan & Baluchestan, Zahedan, P. O. Box 98155-147, Iran.

The present work describes the construction of a new modified graphite-multiwall carbon nanotube paste electrode by casting the appropriate mixture of tetraheptylammonium iodide-iodine as a new modifier. The modified paste electrode was used for the determination of ascorbic acid (AA) in a phosphate buffer solution (pH 2.0). When compared to activated carbon, a graphite and multiwall carbon nanotube paste electrode containing a new modifier, the proposed modified paste electrode not only shifted the oxidation potential of AA towards a less-positive potential but also enhanced its oxidation peak current. Further, the oxidation of AA was highly stable at the modified paste electrode. The optimum analytical conditions were sought. The current response of AA increases linearly while increasing its concentration from 5.6 × 10(-5) to 1.2 × 10(-2) M with a correlation coefficient of 0.9991; the detection limit (3σ) was found to be of 3.6 × 10(-5) M. The present modified paste electrode was also successfully used for the determination of AA in the presence of common interference compounds. The present modified electrode was successfully demonstrated towards the determination of AA in pharmaceutical and food samples.
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http://dx.doi.org/10.2116/analsci.27.929DOI Listing
January 2012

Simultaneous and sensitive determination of a quaternary mixture of AA, DA, UA and Trp using a modified GCE by iron ion-doped natrolite zeolite-multiwall carbon nanotube.

Biosens Bioelectron 2011 Oct 6;28(1):56-63. Epub 2011 Jul 6.

Analytical Research Laboratory, Department of Chemistry, University of Sistan & Baluchestan, PO Box 98155-147, Zahedan, Iran.

The evaluation of a novel modified glassy carbon electrode modified with iron ion-doped natrolite zeolite-multiwalled carbon nanotube for the simultaneous and sensitive determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp) has been described. The measurements were carried out using cyclic voltammetry in buffer solution with pH 1. This modified electrode exhibits potent and persistent electroxidation behavior followed by well-separated oxidation peaks towards AA, DA, UA and Trp with increasing of the oxidation current. For the quaternary mixture containing AA, DA, UA and Trp, the 4 compounds can well separate from each other at the scan rate of 100 mVs(-1) with a potential difference of 270 mV, 150 mV and 260 mV for the oxidation peak potentials of AA-DA, DA-UA and UA-Trp, respectively, which was large enough to simultaneous determine AA, DA, UA and Trp. The catalytic peak current obtained, was linearly dependent on the AA, DA, UA and Trp concentrations in the range of 7.77-833 μM, 7.35-833 μM, 0.23-83.3 μM and 0.074-34.5 μM and the detection limits for AA, DA, UA and Trp were 1.11, 1.05, 0.033 and 0.011 μM, respectively. The analytical performance of this sensor has been evaluated for simultaneous detection of AA, DA, UA and Trp in human serum and urine samples.
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http://dx.doi.org/10.1016/j.bios.2011.06.042DOI Listing
October 2011

Fluorescence and DNA-binding properties of neodymium(III) and praseodymium(III) complexes containing 1,10-phenanthroline.

Spectrochim Acta A Mol Biomol Spectrosc 2011 Sep 7;79(5):978-84. Epub 2011 May 7.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran.

The binding of neodymium(III) and praseodymium(III) complexes containing 1,10-phenanthroline, [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)), to DNA has been investigated by absorption, emission, and viscosity measurements. The complexes show absorption decreasing in charge transfer band, fluorescence decrement when bound to DNA. The binding constant Kb has been determined by absorption measurement for both complexes and found to be (6.76±0.12)×10(4) for 1 and (1.83±0.15)×10(4)M(-1), for 2. The fluorescence of [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)) has been studied in detail. The results of fluorescence titration reveal that DNA has the strong ability to quenching the intrinsic fluorescence of Nd(III) and Pr(III) complexes through the static quenching procedure. The binding site number n, apparent binding constant Kb and the Stern-Volmer constant kSV are determined. Thermodynamic parameters, enthalpy change (ΔH°) and entropy change (ΔS°), are calculated according to relevant fluorescent data and Van't Hoff equation. The experimental data suggest that the complexes bind to DNA by non-intercalative mode. Major groove binding is the preferred mode of interaction for [M(phen)2Cl3·OH2] (M=Nd (1), Pr (2)) with DNA.
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http://dx.doi.org/10.1016/j.saa.2011.04.009DOI Listing
September 2011

Study on fluorescence and DNA-binding of praseodymium(III) complex containing 2,2'-bipyridine.

Spectrochim Acta A Mol Biomol Spectrosc 2011 Jan 30;78(1):389-95. Epub 2010 Oct 30.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran.

The fluorescence of praseodymium(III) complex containing 2,2'-bipyridine, [Pr(bpy)2Cl3·OH2] has been investigated in details. Also, the biological activity of [Pr(bpy)2Cl3·OH2] has been evaluated by examining its ability to bind to DNA with UV-vis, fluorescence as well as viscosity measurement. The fluorescence of [Pr(bpy)2Cl3·OH2] is strongly quenched through static mechanism in the presence of DNA. DNA intrinsic binding constant, Kb the binding site number, n the Stern-Volmer quenching constant, KSV and the thermodynamic parameters have been determined by fluorescence spectroscopy. For characterization of bonding mode, the effect of various experimental parameters were investigated on the interaction of [Pr(bpy)2Cl3·OH2] with DNA.
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http://dx.doi.org/10.1016/j.saa.2010.10.026DOI Listing
January 2011

Determination of cyanide in wastewaters using modified glassy carbon electrode with immobilized silver hexacyanoferrate nanoparticles on multiwall carbon nanotube.

J Hazard Mater 2011 Jan 17;185(1):255-61. Epub 2010 Sep 17.

Analytical Research Laboratory, Department of Chemistry, University of Sistan & Baluchestan, Zahedan, PO Box 98155-147, Iran.

The sensitive determination of cyanide in wastewaters using modified GC electrode with silver hexacyanoferrate nanoparticles (SHFNPs) immobilized on multiwall carbon nanotube (MWCNT) was reported. The immobilization of SHFNPs on MWCNT was confirmed by transmission electron microscopy (TEM). The TEM image showed that the SHFNPs retained the spherical morphology after immobilized on MWCNT. The size of SHFNPs was examined around 27 nm. The GC/MWCNT-SHFNPs was used for the determination of cyanide in borax buffer (BB) solution (pH 8.0). Using square wave voltammetry, the current response of cyanide increases linearly while increasing its concentration from 40.0 nM to 150.0 μM and a detection limit was found to be 8.3 nM (S/N=3). The present modified electrode was also successfully used for the determination of 5.0 μM cyanide in the presence of common contaminants at levels presenting in industrial wastewaters. The practical application of the present modified electrode was demonstrated by measuring the concentration of cyanide in industrial wastewater samples. Moreover, the studied sensor exhibited high sensitivity, good reproducibility and long-term stability.
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http://dx.doi.org/10.1016/j.jhazmat.2010.09.026DOI Listing
January 2011

Simultaneous determination of ascorbic acid and uric acid by a new modified carbon nanotube-paste electrode using chloromercuriferrocene.

Anal Sci 2010 ;26(4):425-30

Analytical Research Laboratory, Department of Chemistry, University of Sistan & Baluchestan, Zahedan, P. O. Box 98155-147, Iran.

The electrochemical behavior of ascorbic acid (AA) and uric acid (UA) at the surface of a multiwall carbon nanotube-paste electrode (MCNTPE) modified with incorporate chloromercuriferrocene (CMF) was investigated. The voltammetric studies using the MCNTPE/CMF electrode show two well-resolved anodic peaks for AA and UA with a potential difference of 430 mV, revealing the possibility of the simultaneous electrochemical detection of these compounds. The optimum analytical conditions were sought. Linear calibration plots were obtained over the range of 8.0 x 10(-6)-6.9 x 10(-4) M and 2.4 x 10(-6)-6.9 x 10(-4) M with detection limits (3sigma) of 2.6 x 10(-6) and 7.9 x 10(-7) M for AA and UA, respectively. The electrode with the best conditions is applied for selective determination of AA and UA in complex biological and clinical matrices.
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http://dx.doi.org/10.2116/analsci.26.425DOI Listing
August 2010

Preparation of silver hexacyanoferrate nanoparticles and its application for the simultaneous determination of ascorbic acid, dopamine and uric acid.

Talanta 2010 Mar 12;80(5):1657-64. Epub 2009 Oct 12.

Analytical Research Laboratory, Department of Chemistry, University of Sistan & Baluchestan, PO Box 98155-147, Zahedan, Iran.

A silver hexacyanoferrate nanoparticles/carbon nanotubes modified glassy carbon electrode was fabricated and then successfully used for the simultaneous determination of ascorbic acid, dopamine and uric acid by cyclic voltammetry. A detailed investigation by transmission electron microscopy (TEM) and electrochemistry was performed in order to elucidate the preparation process and properties of the nanocomposites. The size of silver hexacyanoferrate nanoparticles was examined by TEM around 27 nm. Linear calibration plots were obtained over the range of 4.0 x 10(-6)-7.8 x 10(-5), 2.4 x 10(-6)-1.3 x 10(-4) and 2.0 x 10(-6)-1.5 x 10(-4) mol L(-1) with detection limits of 4.2 x 10(-7),1.4 x 10(-7) and 6.0 x 10(-8) mol L(-1) for ascorbic acid, dopamine and uric acid, respectively. The practical analytical utilities of the modified electrode were demonstrated by the determination of ascorbic acid, dopamine and uric acid in urine and human blood serum samples.
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http://dx.doi.org/10.1016/j.talanta.2009.10.005DOI Listing
March 2010

Fluorescence and DNA-binding spectral studies of neodymium(III) complex containing 2,2'-bipyridine, [Nd(bpy)2Cl(3)xOH2].

Spectrochim Acta A Mol Biomol Spectrosc 2010 Feb 22;75(2):598-603. Epub 2009 Dec 22.

Department of Chemistry, University of Sistan & Baluchestan, Zahedan, Iran.

The interaction of [Nd(bpy)(2)Cl(3)xOH(2)], where bipy is 2,2'-bipyridine, with DNA has been studied by absorption, emission, and viscosity measurements. [Nd(bpy)(2)Cl(3)xOH(2)] showed absorption decreasing in charge transfer band with increasing of DNA. The binding constant, K(b) has been determined by absorption measurement and found to be (1.5+/-0.1)x10(5)M(-1). The fluorescent of [Nd(bpy)(2)Cl(3)xOH(2)] has been investigated in detail. The interaction was also studied by fluorescence quenching technique. The results of fluorescence titration revealed that DNA had the strong ability to quenching the intrinsic fluorescence of Nd(III) complex at 327 nm. The binding site number n, apparent binding constant K(b) and the Stern-Volmer quenching constant K(SV) have been determined. Thermodynamic parameters have been calculated according to relevant fluorescent data and Van't Hoff equation. Characterization of bonding mode has been studied. The results suggested that the major interaction mode between [Nd(bpy)(2)Cl(3)xOH(2)] and DNA was groove binding.
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http://dx.doi.org/10.1016/j.saa.2009.11.024DOI Listing
February 2010

Cyanide uptake from wastewater by modified natrolite zeolite-iron oxyhydroxide system: application of isotherm and kinetic models.

J Hazard Mater 2009 Jul 6;166(2-3):1060-6. Epub 2008 Dec 6.

Department of Chemistry, University of Sistan & Baluchestan, P.O. Box 98155-147, Zahedan, Iran.

A method for the removal of cyanides from wastewater is described. The method involves the adsorption of cyanides by a modified natural zeolite (natrolite) using batch technique. A new iron oxyhydroxide-natrolite system was used in this study. A combination of XRD, XRF and FTIR spectroscopies, as well as TG/DSC thermal analyses was used for characterization of zeolitic materials. Effects of parameters such as pH, amount of adsorbent and contact time on the cyanide removing yield are studied. It was observed that the yield increases by increasing dosage of adsorbent and contact time at a fixed pH 7.5. A yield of 82% was achieved at optimum conditions for removing cyanide from industrial wastewaters. The experimental data obtained for optimum conditions were selected for modeling the adsorption behavior of the materials using six isotherm equations (Freundlich, Langmuir, Langmuir-Freundlich, Dubinin-Radushkevich, Redlich-Peterson and Toth). The obtained modeling results indicated that, although the three-parameter models, taking into account the surface heterogeneity, provided the closest approach to the measurement data, the parameters estimates could be highly biased. The kinetic studies proved that the second-order kinetic was the applicable model.
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http://dx.doi.org/10.1016/j.jhazmat.2008.12.012DOI Listing
July 2009