Publications by authors named "Gholamhassan Azimi"

13 Publications

  • Page 1 of 1

Theoretical insights on the excited-state-deactivation mechanisms of protonated thymine and cytosine.

Phys Chem Chem Phys 2021 Apr 6;23(14):8916-8925. Epub 2021 Apr 6.

Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.

Ab initio and surface-hopping nonadiabatic dynamics simulation methods were employed to investigate relaxation mechanisms in protonated thymine (TH) and cytosine (CH). A few conical intersections were located between ππ* and S states for each system with the CASSCF (8,8) theoretical model and relevant contributions to the deactivation mechanism of titled systems were addressed by the determination of potential energy profiles at the CASPT2 (12,10) theoretical level. It was revealed that the relaxation of the ππ* state of the most stable conformer of both systems to the ground state is mostly governed by the accessible S/S conical intersection resulting from the barrier-free out-of-plane deformation. Interestingly, it was exhibited that the ring puckering coordinate driven from the C position of the heterocycle ring in TH and CH plays the most prominent role in the deactivation mechanism of considered systems. Our ab initio results are also supported by excited-state nonadiabatic dynamics simulations based on ADC(2), describing the ultrashort S lifetime of TH/CH by analyzing trajectories leading excited systems to the ground. It was confirmed that the excited-state population mostly relaxes to the ground via the ring puckering coordinate from the C moiety. Overall, the theoretical results of this study shed light on the deactivation mechanism of protonated DNA bases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/d0cp06673gDOI Listing
April 2021

Excited State Deactivation Mechanism in Protonated Uracil: New Insights from Theoretical Studies.

J Phys Chem A 2020 Jun 12;124(25):5089-5097. Epub 2020 Jun 12.

Department of Chemistry, University of Isfahan, 81746-73441 Isfahan, Iran.

We have conducted here a theoretical exploration, discussing the distinct excited state lifetimes reported experimentally for the two lowest lying protonated isomers of uracil. In this regard, the first-principal computational levels as well as the nonadiabatic surface hopping dynamics have been employed. It has been revealed that relaxation of the ππ* state of enol-enol form (EE) to the ground is barrier-free via out-of-plane coordinates, resulting in an ultrashort S lifetime of this species. For the second most stable isomer (EK), however, a significant barrier predicted in the CASPT2 S potential energy profile along the twisting coordinate has been proposed to explain the relevant long lifetime reported experimentally.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpca.0c02284DOI Listing
June 2020

Bioassay-directed isolation of quaternary benzylisoquinolines from with bactericidal activity against .

Res Pharm Sci 2018 Apr;13(2):149-158

Brucellosis Department, Razi Vaccine and Serum Research Institute, Karaj, I.R. Iran.

Bonge. (Syn: Boiss. & Buhse) is a shrub widely distributed in Middle East and central part of Asia. An ethnobotanical study revealed that indigenous and tribal people in Iran use root decoction for treatment of brucellosis. Therefore, the aim of this study was bioassay directed isolation of antibacterial compounds from this plant based on their bactericidal activity against . Briefly, the ethanol extract of was fractioned and subjected to preliminary antibacterial screening tests against Brucella. The more active fraction (Fr.3) was subjected to purification by repeated chromatography systems. Quaternary benzylisoquinoline alkaloids including columbamine, palmatine, berberine, and jatrorhizine were four main components identified in the selected active fraction. Except for berberine which is reported before, palmatine, columbamine and jatrorhizine are isolated for the first time from this plant. Anti-brucellosis properties of isolated compounds were studied against under different test conditions. In minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) results, jatrorhizine () showed more antibacterial activity with MIC and MBC of 0.78 and 1.56 μg/mL, respectively. In both agar well diffusion and disk diffusion ANOVA results showed that there were statistically significant differences between compounds versus placebo in all of the tested concentration ( <0.001). In conclusion, all of four alkaloids showed potent antibacterial activity against but jatrorhizine and columbamine with free hydroxyl group on C-3 or C-2 showed more activity than palmatine and berberine without any free hydroxyl group on their structures. The antibacterial effects of columbamine (15 μg/mL) and jatrorhizine (15 μg/mL) were comparative to streptomycin (10 μg/mL) as standard drug which candidate them for more pharmacological researches to find new antibacterial agents against brucellosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4103/1735-5362.223797DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5842486PMC
April 2018

Self-recognition of the racemic ligand in the formation of homochiral dinuclear V(V) complex: In vitro anticancer activity, DNA and HSA interaction.

Eur J Med Chem 2017 Jul 22;135:230-240. Epub 2017 Apr 22.

Department of Chemistry, University of Isfahan, Isfahan, 81746-73441, Iran.

The reaction of a racemic mixture of Schiff base tridentate ligand with vanadium(V) affords homochiral vanadium complex, (VO(R-L))O and (VO(S-L))O due to ligand "self-recognition" process. The formation of homochiral vanadium complex was confirmed by H NMR, C NMR and X-ray diffraction. The HSA- and DNA-binding of the resultant complex is assessed by absorption, fluorescence and circular dichroism (CD) spectroscopy methods. Based on the results, the HSA- and DNA-binding constant, K, were found to be 8.0 × 10 and 1.9 × 10 M, respectively. Interestingly, in vitro cytotoxicity assay revealed the potent anticancer activity of this complex on two prevalent cancer cell lines of MCF-7 (IC50 value of 14 μM) and HeLa (IC50 value of 36 μM), with considerably low toxicity on normal human fibroblast cells. The maximum cell mortality of 12.3% obtained after 48 h incubation of fibroblast cells with 100 μM of the complex. Additionally, the specific DNA- and HSA-binding was also shown using molecular docking method. The synthesized complex displayed high potential for biomedical applications especially for development of novel and efficient anticancer agents.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejmech.2017.04.053DOI Listing
July 2017

Protonated serotonin: Geometry, electronic structures and photophysical properties.

Spectrochim Acta A Mol Biomol Spectrosc 2017 Jul 1;182:8-16. Epub 2017 Apr 1.

Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.

The geometry and electronic structures of protonated serotonin have been investigated by the aim of MP2 and CC2 methods. The relative stabilities, transition energies and geometry of sixteen different protonated isomers of serotonin have been presented. It has been predicted that protonation does not exhibit essential alteration on the S←S electronic transition energy of serotonin. Instead, more complicated photophysical nature in respect to its neutral analogue is suggested for protonated system owing to radiative and non-radiative deactivation pathways. In addition to hydrogen detachment (HD), hydrogen/proton transfer (H/PT) processes from ammonium to indole ring along the NH⋯π hydrogen bond have been predicted as the most important photophysical consequences of SERH at S excited state. The PT processes is suggested to be responsible for fluorescence of SERH while the HD driving coordinate is proposed for elucidation of its nonradiative deactivation mechanism.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.saa.2017.03.069DOI Listing
July 2017

Synthesis, characterization and separation of chiral and achiral diastereomers of Schiff base Pd(II) complex: A comparative study of their DNA- and HSA-binding.

J Photochem Photobiol B 2016 Oct 25;163:246-60. Epub 2016 Aug 25.

Department of Biotechnology, Faculty of Advanced Sciences and Technologies, University of Isfahan, Isfahan, Iran.

A racemic mixture of a new chiral Schiff base ligand (HL: R/S-(1-phenylethylimino)methylnaphtalen-2-ol) has been utilized to prepare Pd(II) complex. Crystallization technique has been employed to separate diastereomeric pairs of Pd(II) complex: (mesoPdL2) and (racPdL2) that in this paper are known as PdL2(1) and PdL2(2), respectively. The synthesized complexes have been characterized by means of elemental analysis (CHN), FT-IR, (1)H and (13)C NMR spectroscopies. Moreover, PdL2(1) has been structurally characterized by single-crystal X-ray diffraction. The geometry around the metal center is square-planar. The interaction of two diastereomers of Pd(II) complex with FS-DNA has been explored, using UV-vis spectroscopy, fluorescence quenching, chemometrics and viscosity measurement methods. The PdL2(1) exhibited higher binding constant, about 10-fold, (1.0×10(6)M(-1)) as compared to PdL2(2) (1.51.5×10(5)M(-1)). Moreover, the human serum albumin (HSA) binding ability has been monitored by absorption, quenching of tryptophan fluorescence emission and circular dichroism (CD) studies. The slight difference is observed between HSA binding affinity with the complexes: PdL2(1) (6.2×10(4)M(-1)) and PdL2(2) (3.3×10(4)M(-1)). Also, the thermodynamic parameters were determined at three different temperatures (298, 308 and 318K). In this study, molecular docking was also carried out to confirm and illustrate the specific DNA- and HSA-binding of the Pd(II) complexes. In the PdL2(1)-HSA system a T-shaped π-π interaction with PHE206 was observed. While in the PdL2(2)-HSA system there are a hydrogen bond, a π-cation and two T-shaped π-π interactions with ASB324, LYS212 and PHE228, respectively. The groove binding mode of DNA interaction has been proposed for both diastereomers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jphotobiol.2016.08.035DOI Listing
October 2016

Electronically Excited States of Neutral, Protonated α-Naphthol and Their Water Clusters: A Theoretical Study.

J Phys Chem A 2015 Jun 15;119(25):6650-60. Epub 2015 Jun 15.

Department of Chemistry, University of Isfahan, 81746-73441, Isfahan, Iran.

The RI-MP2 and RI-CC2 methods have been employed to determine the potential energy profiles of neutral and protonated α-naphthol, in their individual forms and microhydrated with 1 and 3 water molecules, at different electronic states. According to calculated results, it has been predicted that dynamics of nonradiative processes in protonated α-naphthol is essentially different from that of its neutral homologue. In protonated α-naphthol, the calculations reveal that (1)σπ* state, is the most important photophysical state, having a bound nature with a broad potential curve along the OH coordinate of isolated system, while it is dissociative in monohydrated homologue. In neutral system, similar to phenol, the (1)πσ* state, plays the fundamental relaxation role along the O-H stretching coordinate. Moreover, microhydration strongly affects the photophysical properties of α-naphthol, mostly by alteration of the (1)ππ* PE profile, from a bound state in an isolated analogue to a dissociative state in hydrated systems. Furthermore, it has been found that three water molecules are necessary for ground state proton transfer between protonated α-naphthol and water; with a small barrier; (ΔE< 0.1 eV).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jpca.5b02249DOI Listing
June 2015

Photophysics and photochemistry of cis- and trans-hydroquinone, catechol and their ammonia clusters: a theoretical study.

Photochem Photobiol Sci 2015 Feb;14(2):457-64

Department of Chemistry, University of Isfahan, 81746-73441 Isfahan, Iran.

Excited state hydrogen transfer in hydroquinone- and catechol-ammonia clusters has been extensively investigated by high level ab initio methods. The potential energy profiles of the title systems at different electronic states have been determined at the MP2/CC2 levels of theory. It has been predicted that double hydrogen transfer (DHT) takes place as the main consequence of photoexcited tetra-ammoniated systems. Consequently, the DHT processes lead the excited systems to the (1)πσ*-S0 conical intersections, which is responsible for the ultrafast non-radiative relaxation of UV-excited clusters to their ground states. Moreover, according to our calculated results, the single hydrogen detachment or hydrogen transfer process essentially governs the relaxation dynamics of smaller sized clustered systems (mono- and di-ammoniated).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1039/c4pp00356jDOI Listing
February 2015

Optimization and application of microwave-assisted acid hydrolysis for rapid quantification of protein oxidation markers using LC-MS.

Talanta 2011 Sep 21;85(4):1835-41. Epub 2011 Jul 21.

Institute of Analytical Chemistry and Food Chemistry, Graz University of Technology, Stremayrgasse 9, 8010 Graz, Austria.

Simple and efficient microwave-assisted acid hydrolysis (MAAH) of proteins was used for rapid quantification of α-aminoadipic semialdehyde (AAS) and γ-glutamic semialdehyde (GGS) as major protein oxidation markers. The precursor amino acid residues corresponding to AAS and GGS in oxidized proteins were derivatized by reductive amination with sodium cyanoborohydride (NaCNBH(3)) and p-aminobenzoic acid (ABA) followed by MAAH to generate the marker derivatives AAS-ABA and GGS-ABA. The quantification was performed using electrospray ionization liquid chromatography-mass spectrometry (ESI LC-MS). The important parameters for hydrolysis were optimized, which include the temperature, the reaction time, the acid concentration and volume as well as the microwave power. Compared to the conventional acid hydrolysis of 18-24h using 6-12 M HCl at 110°C applied commonly in the literature and also in this work, MAAH of proteins can be completed as fast as in only 2-10 min and, additionally, with a 3-5 times higher yield of the final derivatization products. Furthermore, a better agreement between the ratio of the detected derivatization products and the theoretical yields from the studied protein has also been achieved, which indicates that MAAH may serve as a more reliable method of acid hydrolysis for this purpose than that with conventional thermal heating. The MAAH method is demonstrated to be a time-saving, reproducible and efficient technique for studying AAS and GGS as protein oxidation markers using LC-MS.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.talanta.2011.07.050DOI Listing
September 2011

A QSAR study for modeling of 8-azaadenine analogues proposed as A1 adenosine receptor antagonists using genetic algorithm coupling adaptive neuro-fuzzy inference system (ANFIS).

Anal Sci 2010 ;26(8):897-902

Department of Chemistry, University of Arak, Iran.

A quantitative structure activity relationship (QSAR) study of 8-azaadenine, as antagonists for the A1 receptor, is described. A genetic algorithm (GA) method was used as the feature selection tool, and an adaptive neuro-fuzzy inference system (ANFIS) was employed for feature mapping. The best descriptors (GATS4v and BELv7) were applied to train the ANFIS model. The optimum number and shape of related functions were obtained through a subtractive clustering algorithm. The ability and robustness of the GA-ANFIS model in predicting the affinity of 8-azaadenine derivatives (pK(i)) are illustrated by validation techniques of Leave One Out, heuristic and randomized methods. The results have indicated that the proposed model of ANFIS in this work is superior over two other methods, radial basis function (RBF) and multiple linear regression (MLR).
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2116/analsci.26.897DOI Listing
December 2010

In situ monitoring of pH titration by Raman spectroscopy.

Spectrochim Acta A Mol Biomol Spectrosc 2010 May 4;75(5):1403-10. Epub 2010 Feb 4.

Raman Spectroscopy Group, University Analytical Centre, Division of Chemical and Forensic Sciences, University of Bradford, West Yorkshire BD7 1DP, UK.

Molecular speciation of organic compounds in solution is essential for the understanding of ionic complexation. The Raman technique was chosen because it allows the identification of compounds in different states, and it can give information about the molecular geometry from the analysis of the vibrational spectra. The effect of pH on organic compounds can give information about the ionisation of molecule species. In this study the ionisation steps of salicylic acid and paracetamol have been studied by means of potentiometry coupled with Raman spectroscopy at 30.0 degrees C in a solution of ionic strength 0.96moldm(-3) (KNO(3)) and 0.04moldm(-3) (HNO(3)). The protonation and deprotonation behaviour of the molecules were studied in different pH regions. The abundance of the three different species in the Raman spectra of aqueous salicylic acid have been identified satisfactorily, characterised, and determined by numeric treatment of the data using a multiwavelength curve-fitting program and confirmed with the observed spectral information.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.saa.2010.01.008DOI Listing
May 2010

Spectrophotometric determination of trace amounts of fluoride using an Al-xylenol orange complex as a colored reagent.

Anal Sci 2009 Oct;25(10):1249-53

Department of Chemistry, Faculty of Science, Arak University, Arak 38156-879, Iran.

A new spectrophotometric reagent for the determination of trace amounts of fluoride has been introduced. This method is based on the decolorization of a complex of Al(III) with xylenol orange (XO) as an ultra-sensitive colored reagent. Since the Al-XO complex plays an important role in this method, the protonation and complexation of XO with Al(III) at an ionic strength of 0.1 mol L(-1) at 25 degrees C has been studied by a spectrophotometric global analysis method. The EQUISPEC program was used to evaluate the protonation constants of XO and the stability constants of the formed complexes with Al(III). The protonation and the stability constants of the major complex species such as ML, MLH and MLH2, were determined. Finally, a spectrophotometric method for the assay of fluoride based on a decrease of the color intensity of the Al-XO complex, in an aqueous solution has been designed. The effects of some important variables on the determination of fluoride based on the proposed method were investigated. The method was applied to the determination of fluoride under the optimum conditions (pH 5.2, ionic strength 0.1 mol L(-1), 25 degrees C). The determination of fluoride in the range of 0.08-1.4 microg mL(-1) (SD = 1.2%) was successfully performed. Interferences of Fe(III) were easily eliminated by using ascorbic acid. The proposed method was applied to the determination of trace amounts of fluoride content of some real water samples.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2116/analsci.25.1249DOI Listing
October 2009

Solid phase selective and extractive preconcentration of silver ion from aqueous samples on modified silica gel with 5-(4-dimethylaminobenzylidene)-rhodanine; prepared by sol-gel method.

Anal Sci 2009 May;25(5):711-6

Department of Chemistry, Faculty of Sciences, University of Arak, Iran.

A new modified silica gel doped with 5-(4-dimethylaminobenzylidene)-rhodanine was prepared for separation, preconcentration and determination of silver ion by atomic absorption spectrometry. This new modified silica gel was used as an effective adsorbent for the solid phase extraction of Ag(+) from aqueous solutions. The variables that influence the adsorption/desorption of trace levels of Ag(+) were optimized in the column process. The preconcentration factor and capacity of the adsorbent at optimum conditions were found as 220 and 420 microg Ag(+) per gram of adsorbent, respectively. The relative standard deviation and the detection limit for measurement of Ag(+) in our experiments were less than 1.5% (n = 10) and 0.02 microg L(-1), respectively. Common coexisting ions did not interfere with the separation and determination of silver ion. The proposed method was successfully applied for preconcentration and determination of silver ion in some spiked water samples.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2116/analsci.25.711DOI Listing
May 2009
-->