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    Theoretical investigation on antioxidant activity of bromophenols from the marine red alga Rhodomela confervoides: H-atom vs electron transfer mechanism

    , Article Journal of Agricultural and Food Chemistry ; Volume 61, Issue 7 , 2013 , Pages 1534-1541 ; 00218561 (ISSN) Javan, A. J ; Javan, M. J ; Tehrani, Z. A ; Sharif University of Technology
    2013
    Abstract
    Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired... 

    Facile synthesis of highly substituted 2-pyrone derivatives via a tandem Knoevenagel condensation/lactonization reaction of β-formyl-esters and 1,3-cyclohexadiones

    , Article Tetrahedron Letters ; Vol. 55, issue. 18 , April , 2014 , p. 2908-2911 ; ISSN: 00404039 Moghaddam, F. M ; Mirjafary, Z ; Javan, M. J ; Motamen, S ; Saeidian, H ; Sharif University of Technology
    Abstract
    A mild and efficient tandem process for the synthesis of new highly substituted 2-pyrones starting from commercially available 2-arylacetic acids has been developed. The synthesis is based on the Knoevenagel condensation of 1,3-cyclohexadiones with various β-formyl-esters, followed by lactonization in the presence of nano ZnO (20 mol %). Moderate to high yields and readily available cheap starting materials are the key features of the present method  

    Interactions of glutathione tripeptide with gold cluster: Influence of intramolecular hydrogen bond on complexation behavior

    , Article Journal of Physical Chemistry A ; Volume 116, Issue 17 , 2012 , Pages 4338-4347 ; 10895639 (ISSN) Tehrani, Z. A ; Jamshidi, Z ; Javan, M. J ; Fattahi, A ; Sharif University of Technology
    2012
    Abstract
    Understanding the nature of the interaction between metal nanoparticles and biomolecules has been important in the development and design of sensors. In this paper, structural, electronic, and bonding properties of the neutral and anionic forms of glutathione tripeptide (GSH) complexes with a Au 3 cluster were studied using the DFT-B3LYP with 6-31+G**-LANL2DZ mixed basis set. Binding of glutathione with the gold cluster is governed by two different kinds of interactions: Auâ€"X (X = N, O, and S) anchoring bond and Au··•·•H-X nonconventional hydrogen bonding. The influence of the intramolecular hydrogen bonding of glutathione on the interaction of this peptide with the gold cluster has been... 

    Effect of cation radical formation on reactivity and acidity enhancement of cytosine nucleobase: Natural bond orbital and atom in molecule analysis

    , Article Journal of Theoretical and Computational Chemistry ; Volume 11, Issue 2 , 2012 , Pages 313-327 ; 02196336 (ISSN) Tehrani, Z. A ; Javan, M. J ; Fattahi, A ; Hashemi, M. M ; Sharif University of Technology
    Abstract
    The radical cations of DNA constituents generated by the ionizing radiation initiate an alteration of the bases, which is one of the main types of cytotoxic DNA lesions. These cation radical spices are known for their role in producing nucleic acid strand break. In this study, the gas-phase intrinsic chemical properties of the gaseous radical cations of cytosine and its base pair with guanine were examined by employing density functional theory (B3LYP) with the 6-311++G(d,p) basis set. Structures, geometries, adiabatic ionization energies, adiabatic electron affinities, charge distributions, molecular orbital analysis and proton-transfer process of these molecules were investigated. The... 

    DFT study on conformational behavior of hydrogen ion abstractions of cytosine nucleosides: AIM and NBO analysis

    , Article Journal of Theoretical and Computational Chemistry ; Volume 10, Issue 6 , 2011 , Pages 803-817 ; 02196336 (ISSN) Tehrani, Z. A ; Fattahi, A ; Javan, M. J ; Hashemi, M. M ; Sharif University of Technology
    Abstract
    In this paper, we explore theoretically energetic and structural properties of the possible cations formed via hydride ion abstraction at various sites of sugar part of cytosine nucleosides by employing B3LYP exchange-correlation functional with 6-311++G (d,p) orbital basis sets. In general, the hydride ion abstracted sugar cations of cytosine nucleosides have the following stability sequence: caH2′ > caH1′ > caH3′ > caH4′ > caH5′ for cytidine and caH1′ > caH4′ > caH3′ > caH5′ > caH2′ for deoxycytidine. Furthermore, the effect of solvent environment on the stability order of cations integral equation formalism of the polarized model (IEF-PCM) was employed to model aqueous solution. The... 

    Structures, stabilities & conformational behaviors of hydrogen-atom abstractions of cytosine nucleosides: AIM & NBO analysis

    , Article Computational and Theoretical Chemistry ; Volume 971, Issue 1-3 , September , 2011 , Pages 19-29 ; 2210271X (ISSN) Tehrani, Z. A ; Javan, M. J ; Fattahi, A ; Hashemi, M. M ; Sharif University of Technology
    2011
    Abstract
    Abstraction of hydrogen atom from DNA and RNA subunits leads to formation of a neutral radical. The formation of these radicals can lead to harmful structural alternations and formation of multiple lesions in helixes of DNA and RNA. In the present work, we explore theoretically energetic and structural properties of the possible radicals formed via hydrogen atom abstraction at various sites of sugar part of cytosine nucleosides by employing B3LYP exchange-correlation functional with 6-311++G (d,p) orbital basis sets. Two types of free radicals may be found by hydrogen abstraction of sugar part of cytosine nucleosides: carbon centered radicals and the oxygen centered radicals. The computation...