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Item STRUCTURE AND REACTIVITY OF HALOGENATED GC PNA BASE PAIRS – A DFT APPROACH (Article)(Editorial board of Journal of Experimental Biology and Agricultural Sciences, 2023-11-30) Ranjithkumar, Rajamani; Indumathi, K; Srimathi, P; Praveena, G; Ling, Shing Wong; Sinouvassane, DjearamaneThe present study explored the structural and reactivity relationship of halogenated G-C PNA base pairs using density functional theory (DFT) calculations. The halogens such as F, Cl, and Br are substituted by replacing H atoms involved in H-bonds of the base pairs. All structures were optimized using the B3LYP/6-311++G** theory level, and positive frequencies confirmed their equilibrium states. To understand the structural variations of the considered halogenated systems, the bond distances of R─X, R─H, and X/H•••Y and the bond angles of R─X•••Y were analyzed. The obtained structural parameters and interaction energies are comparable with the previous theoretical reports. In addition, the interaction energies (Eint) and quantum molecular descriptors (QMD) are also calculated to understand the difference between halogenated PNA systems and their non-halogenated counterparts. In this study, the enhancement in the reactivity properties of halogenated PNA systems has been demonstrated, which indicates their improved responsive characteristics in various chemical reactions. Based on the available results, the halogenated PNA systems, carefully considering their substitutional position, facilitate better accommodation for the triplex formation of dsDNA/dsRNA. Therefore, it is concluded that the improved reactivity properties of halogenated PNA base pairs would make them potential candidates for various biological applications.Item STRUCTURE AND REACTIVITY OF HALOGENATED GC PNA BASE PAIRS – A DFT APPROACH(Journal of Experimental Biology and Agricultural Sciences, 2023-11-30) Ranjithkumar, Rajamani; Indumathi, K; Srimathi, P; Praveena, G; Ling Shing, Wong; Sinouvassane, DjearamaneThe present study explored the structural and reactivity relationship of halogenated G-C PNA base pairs using density functional theory (DFT) calculations. The halogens such as F, Cl, and Br are substituted by replacing H atoms involved in H-bonds of the base pairs. All structures were optimized using the B3LYP/6-311++G** theory level, and positive frequencies confirmed their equilibrium states. To understand the structural variations of the considered halogenated systems, the bond distances of R─X, R─H, and X/H•••Y and the bond angles of R─X•••Y were analyzed. The obtained structural parameters and interaction energies are comparable with the previous theoretical reports. In addition, the interaction energies (Eint) and quantum molecular descriptors (QMD) are also calculated to understand the difference between halogenated PNA systems and their non-halogenated counterparts. In this study, the enhancement in the reactivity properties of halogenated PNA systems has been demonstrated, which indicates their improved responsive characteristics in various chemical reactions. Based on the available results, the halogenated PNA systems, carefully considering their substitutional position, facilitate better accommodation for the triplex formation of dsDNA/dsRNA. Therefore, it is concluded that the improved reactivity properties of halogenated PNA base pairs would make them potential candidates for various biological applications.Item EFFECT OF PEPTIDIC BACKBONE ON THE NUCLEIC ACID DIMERIC STRANDS(Taylor & Francis Online, 2020) Indumathi, K; Abiram, A; Praveena, GThis study explores the effect of N-(2-aminoethyl)-glycine peptide chain incorporated at the backbone of nucleic acid dimeric strands on the basis of reactivity descriptors. The structures of obtained PNA dimeric strands were examined through backbone (α, β, γ, δ, ε and ω) and linker (χ1, χ2 and χ3) torsions. The calculated torsions were found to coincide well the available experimental and theoretical data. The peptidic chain incorporated nucleic acid dimers show a drastic change in global reactivity descriptor (gr) values. The vertical ionisation potential (VIP) and polarizability (α′) of peptide chain incorporated Guanine constructs are found to be higher by about 0.24 eV and 98.49 Å3 than their natural counterparts. The obtained gr along with frontier molecular orbitals depict G-containing dimeric strands to have efficient donor and acceptor capability with improved sensitivity upon peptide chain inclusion. This study in general could serve as a basic tool to understand the reactivity properties of PNA modularities, which are the possible building blocks of extended nanostructures.Item EXPLORING THE STRUCTURE AND STABILITY OF Β-DIPEPTIDE – A QUANTUM CHEMICAL AND MOLECULAR DYNAMICS STUDY(Indian Journal of Pure & Applied Physics, 2018-07) Abiram, A; Praveena, GDensity functional theory (DFT) calculations followed by molecular dynamics study has been performed to analyze the structure and stability of β-dipeptide structures in aqueous medium. From DFT study, three local minima with folded conformations and one local minimum with unfolded conformation have been identified. In gas phase, the most stable β-dipeptide has a folded conformation with a weak hydrogen bonding. The interaction of water molecules, approximated from the first solvation shell, also confirms the folded conformation to be the most stable structure. The DFT optimized β-dipeptide conformers have been simulated in explicit water to evaluate the tendency of folded and unfolded state formation. Simulations confirmed the transition of the structure from folded to unfolded and vice versa and further indicated the former to happen rapidly within a few pico second time scale.