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    • List of Articles Behzad Chahkandi

      • Open Access Article

        1 - Theoretical investigation of tautomerisation of 3-Amino-1H-1,2,4-Triazol-5(4H)-One by using quantum calculations by DFT method.
        بهزاد چهکندی
        در این تحقیق بررسی توتومریزاسیون و حالت‌های گذار مولکول 3-آمینو-1H-4،2،1- تری‌آزول-5)4H (- اٌن که حاصل از انتقالات 1و3 پروتون بین اتم های اکسیژن و نیتروژن است با استفاده از محاسبات کوانتومی در سطح محاسباتیDFT-B3LYP/6-311++G(d,p)، در فاز گازی و در محیطی با حضور یک و دو م More
        در این تحقیق بررسی توتومریزاسیون و حالت‌های گذار مولکول 3-آمینو-1H-4،2،1- تری‌آزول-5)4H (- اٌن که حاصل از انتقالات 1و3 پروتون بین اتم های اکسیژن و نیتروژن است با استفاده از محاسبات کوانتومی در سطح محاسباتیDFT-B3LYP/6-311++G(d,p)، در فاز گازی و در محیطی با حضور یک و دو مولکول آب انجام شده است. بدین منظور ساختار بهینه توتومرهای مختلف مولکول مورد نظر بدست آمده‌اند. همچنین با استفاده از محاسبات فرکانس در سطح محاسباتی مشابه، خواص ترمودینامیکی تعادل‌های مختلف توتومری از قبیل E∆، H∆، G∆ وKeq بدست آمده‌اند. سپس با استفاده از روش‌های QST2 و QST3 حالت های گذار تعادل‌های توتومری مختلف مولکول3-آمینو-1H-4،2،1- تری‌آزول-5)4H (- اٌن و مقادیر سینتیکی و ترمودینامیکی آنها محاسبه شده‌اند. اثرات تونل‌زنی نیز بر روی سرعت واکنش‌های مربوطه بررسی شده‌اند. نتایج نشان میدهند ثابت سرعت واکنش‌های توتومری مورد بررسی نسبت به اثرات تونل‌زنی حساسیت بالایی دارند و سرعت واکنش های توتومری در حدود چهار تا پنج برابر افزایش می‌یابند. همچنین محاسبات حالت گذارنشان می دهند در غیاب مولکول‌های آب سد انرژی مقدار بالایی دارد و سرعت واکنش های توتومری عمدتاً بدون حضور کاتالیزور خیلی آهسته بوده به عبارتی انجام‌پذیر نیستند. Manuscript profile
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        2 - Investigation of C-O tautomerism in a derivative of Flucytosine: A DFT study
        بهزاد چهکندی
        In this research investigation of tautomerism and transition states of 6-Hydroxy 5-Flourocytosine from 1,3 proton transfer between oxygen and carbon atoms in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by quan More
        In this research investigation of tautomerism and transition states of 6-Hydroxy 5-Flourocytosine from 1,3 proton transfer between oxygen and carbon atoms in the gas phase and in solution and in a micro hydrated environment with 1-3 water molecules was performed by quantum calculations at the DFT/B3LYP/6-31++G(d,p) level of theory. For this purpose, the optimized geometries of various tautomers of the desired molecule were obtained. Also by using frequency calculations at the same level thermodynamic properties of different tautomeric equilibriums such as ΔE, ΔH, ΔG and Keq were obtained. Then transition states of various tautomeric interconversion of 6-Hydroxy 5-Flourocytosine and it’s kinetic and thermodynamic amounts were calculated by QST2 and QST3 methods. And also the tunneling effects on rates of reaction were investigated. The results show in both gas phase and solution, rate constants of tautomeric reactions have high sensitivity on tunneling effects and rate of tautomeric interconversion increase by about five or more. Also transition state calculations show in absence of water assisted molecules the tautomeric interconversion reacctions have high barrier energy and so are very slow, in other word they can not be done Manuscript profile
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        3 - Quantitative Structure-Property Relationship Study for Prediction of the Solvent Polarity Using Quantum Mechanics Descriptors and Support Vector Machine
        mehdi nekoei بهزاد چهکندی
        Quantitative structure-property relationship (QSPR) study for prediction of the polarity some of solvents using quantum mechanics descriptors and support vector machine. Experimental S′ values for 69 solvents were assembled. This set included saturated and unsatur More
        Quantitative structure-property relationship (QSPR) study for prediction of the polarity some of solvents using quantum mechanics descriptors and support vector machine. Experimental S′ values for 69 solvents were assembled. This set included saturated and unsaturated hydrocarbons, solvents containing halogen, cyano, nitro, amide, sulfide, mercapto, sulfone, phosphate, ester, ether, etc. After drawing the structure of the molecules, the suitable molecular descriptors were calculated. Then, the stepwise multiple linear regressions (SW-MLR) variable selection method was subsequently employed to select and implement the prominent descriptors having the most significant contributions to the polarity of the molecules. At first, multiple linear regressions (MLR) model was constructed. Then, support vector machine (SVM) model was used for to obtain better results. A comparison of results by the two methodologies indicated the superiority of SW-SVM over the SW-MLR method. Manuscript profile
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        4 - Conformational analysis of For-L-Ser-L-Ala-NH2 protected dipeptide using quantum calculations: A DFT study
        Behzad Chahkandi Rezvan Mohammad Abadi Mehdi Nekoei
        IIn this study conformational analysis of HCO-Ser-Ala-NH2 dipeptide were performed using DFT method at the B3LYP/6-31G(d) level of theory. For this purpose 54 conformations of serine-alanine protected dipeptide that derived from varying the backbone and sidechain dihedr More
        IIn this study conformational analysis of HCO-Ser-Ala-NH2 dipeptide were performed using DFT method at the B3LYP/6-31G(d) level of theory. For this purpose 54 conformations of serine-alanine protected dipeptide that derived from varying the backbone and sidechain dihedral angles ( and ), were optimized. Then by using frequency calculations at the same level of calculations the stable conformers and thermodynamic values were obtained. Of the 54 considered conformations in this research, 35 conformations were found and 19 conformers were not found. Those that were not found have converged to a different geometry of lower energy and greater stability. Among 35 found conformers the and have the lowest and highest relative energy respectively, therefore are the most stable and unstable conformers respectively. The relative energy of is 14.64 kcalmol-1. The migration pattern show that of the 19 not found conformers with and general structures, migration to is more favorable. Keywords: Dipeptide model; For-Ser-Ala-NH2; Ramachandran plot; sidechain; DFT. Manuscript profile
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        5 - Theoretical study on the kinetics and mechanism of the atmospheric oxidation of acenaphthylene initiated by hydroxyl radical. Hydrogen Abstraction pathway
        maryam talebi Ehsan Zahedi Abolfazl Shiroudi Behzad Chahkandi
        In this research kinetics and mechanism of the atmospheric hydrogen abstraction of acenaphthylene initiated by hydroxyl radical has been investigated theoretically at the MN15L/aug-cc-pVTZ level of theory. The hydrogen abstraction from the four possible positions are ex More
        In this research kinetics and mechanism of the atmospheric hydrogen abstraction of acenaphthylene initiated by hydroxyl radical has been investigated theoretically at the MN15L/aug-cc-pVTZ level of theory. The hydrogen abstraction from the four possible positions are exergonic and exothermic processes. The rate constants (with and without correction by quantum tunneling effects of Wigner and Eckart), activation energies, and activation themodynamic parameters indicated that hydrogen abstraction of acenaphthylene by hydroxyl radical from 4 pathways are kinetically controlled. The values of branching ratios exhibited that the products of hydrogen abstraction reactions from positions 2, 3, and 4 can be observed. . . Manuscript profile
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        6 - Modeling and quantitative structure-activity study of some carboxylate derivatives as anticancer drugs using multivariate linear regression and artificial neural networks
        mehdi nekoei Mahmood Ebrahimi پرستو فتاحی Behzad Chahkandi
        Chemotherapy is one of the most effective treatments for cancers, but many cancers become resistant to the therapeutic effects of a drug during treatment with chemotherapy, which is called Multi Drug Resistance. Currently, some new drugs, including carboxylate derivativ More
        Chemotherapy is one of the most effective treatments for cancers, but many cancers become resistant to the therapeutic effects of a drug during treatment with chemotherapy, which is called Multi Drug Resistance. Currently, some new drugs, including carboxylate derivatives, have been used to reduce drug resistance. In the present study, a structure-activity quantitative relationship (QSAR) study was performed to predict the drug activity of some carboxylate derivatives using multivariate linear regression (MLR) and artificial neural networks (ANN). First, the structure of drug compounds, drawing and appropriate group of descriptors were calculated. Then, the step selection method was used to obtain the best descriptors that were most related to the drug activity of the compounds. First, the linear model of multiple linear regression (MLR) was developed. ANN was then used to obtain better results. Statistical data show the superiority of ANN method over MLR method. Manuscript profile
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        7 - Theoretical investigation of Curtius rearrangement of oxalyl di azide molecule using quantum calculations in gas phase and solution
        Roghaye Taheryan بهزاد چهکندی Ehsan Zahedi
        In this study, was investigated the Curtius rearrangement reaction of the molecule oxalyl diazide (ODA) for syn-syn and anti-anti-conformers in the gas and solvent phases ( water and cyclohexane ). the syn-syn and anti-anti-ODA conformers and transition states related t More
        In this study, was investigated the Curtius rearrangement reaction of the molecule oxalyl diazide (ODA) for syn-syn and anti-anti-conformers in the gas and solvent phases ( water and cyclohexane ). the syn-syn and anti-anti-ODA conformers and transition states related to their rearrangement reactions are optimized in the gas phase using by Density functional theory (DFT) at computational levels WB97XD, M06-2X, B3LYP and the basis sets 6-311 ++ G (2d, d, p) and the CBS-QB3 method .in the solvent phase, calculations have been performed at the level of B3LYP / 6-311 ++ G (2d, d, p).the syn-syn conformer through a concerted mechanism and anti-anti-conformer using a stepwise mechanism product Carbonyl di isosyanate (CAI) , respectively by passing 1 and 2 transition states under curtius rearrangement.in the concerted mechanism the Gibbs free activation energy of the path went is less than the return path of the reaction, in other words, the Gibbs free activation energy of the return path is about 4 times the path went reaction.in the step wise mechanism, the first stage is the endothermic and the second stage is the exothermic process. Manuscript profile
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        ch چهکندی بهزاد چهکندی
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        مهدی نکوئی مهدی مهام بهزاد چهکندی محسن بابازاده
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        مبارکه شمسیان سعید رضا امامیان بهزاد ch
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        بهزاد چهکندی
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        بهزاد چهکندی علی محبوبی فر مجید محمد حسینی
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        مجید محمد حسینی مهدی نکوئی بهزاد چهکندی حسین علی مشایخی مهدی رحیمی
      • Open Access Article

        14 - Theoretical investigation of β-turn structures of serine-alanine protected dipeptide using quantum calculations
        Behzad Chahkandi
             In this research the β-turn structures of L form of serine-alanine protected dipeptide on Ramachandran map were investigated using quantum calculations at the  B3LYP/6-311+G(d,p) and M06-2X/6-311+G(d,p) levels of theory in gas phase. A More
             In this research the β-turn structures of L form of serine-alanine protected dipeptide on Ramachandran map were investigated using quantum calculations at the  B3LYP/6-311+G(d,p) and M06-2X/6-311+G(d,p) levels of theory in gas phase. Amongst of 243 plossible conformers of N-For-ser-ala-NH2 protected dipeptide, 26 of the found conformers having β-turn structures. The quantum theory of atoms in molecules were carried out to characterize the nature of the intramolecular hydrogen bonding in β-turn structures. The obtained results reveal that the  conformer of type V because of including of three HBs is the most stable one between all β-turn structures. However, the most unstable ( ) β-turn conformer of type I bears two and one HBs at the B3LYP and M06-2X levels of theory, respectively. Manuscript profile